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  • 1.
    Bhagavathiachari, Muthuraaman
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Elumalai, Viswanathan
    Vlachopoulos, Nick
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 40, p. 17419-17425Article in journal (Refereed)
    Abstract [en]

    Recently, cobalt redox electrolyte mediators have emerged as a promising alternative to the commonly used iodide/triiodide redox shuttle in dye-sensitized solar cells (DSCs). Here, we report the successful use of a new quasi-liquid, polymer-based electrolyte containing the Co3+/Co2+ redox mediator in 3-methoxy propionitrile solvent in order to overcome the limitations of high cell resistance, low diffusion coefficient and rapid recombination losses. The performance of the solar cells containing the polymer based electrolytes increased by a factor of 1.2 with respect to an analogous electrolyte without the polymer. The performances of the fabricated DSCs have been investigated in detail by photovoltaic, transient electron measurements, EIS, Raman and UV-vis spectroscopy. This approach offers an effective way to make high-performance and long-lasting DSCs.

  • 2.
    Cappel, Ute B.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Liu, Peng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Fredrik O. L.
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Philippe, Bertrand
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Lindblad, Andreas
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Rensmo, Hakan
    Uppsala Univ, Div Mol & Condensed Matter Phys, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Electronic Structure Characterization of Cross-Linked Sulfur Polymers2018In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 9, p. 1041-1047Article in journal (Refereed)
    Abstract [en]

    Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.

  • 3.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Marton, Andras
    Johns Hopkins University.
    Narducci-Sarjeant, Amy A.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Influence of ion pairing on the oxidation of iodide by MLCT excited states2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 15, p. 3830-3838Article in journal (Refereed)
    Abstract [en]

    The oxidation of iodide to diiodide, I2[radical dot]-, by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)3]2+, where deeb is 4,4[prime or minute]-(CO2CH2CH3)2-2,2[prime or minute]-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)3]2+ were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)3]2+* and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (KD = 1.0 +/- 0.01 [times] 105 M-1, kq = 4.8 [times] 1010 M-1 s-1). Excited state reactivity was observed to be the result of reductive quenching that yielded the reduced ruthenium compound, [Ru(deeb-)(deeb)2]+, and the iodine atom, I[radical dot]. In dichloromethane, excited state quenching was primarily static (photoluminescence amplitude quenching) and [Ru(deeb-)(deeb)2]+ formed within 10 ns, consistent with the formation of ion pairs in the ground state that react rapidly upon visible light absorption. In both solvents the appearance of I2[radical dot]- could be time resolved. In acetonitrile, the rate constant for I2[radical dot]- growth, 2.2 +/- 0.2 [times] 1010 M-1 s-1, was found to be about a factor of two slower than the formation of [Ru(deeb-)(deeb)2]+, indicating it was a secondary photoproduct. The delayed appearance of I2[radical dot]- was attributed to the reaction of iodine atoms with iodide. In dichloromethane, the growth of I2[radical dot]-, 1.3 +/- 0.4 [times] 1010 M-1 s-1, was similar to that in acetonitrile, yet resulted from iodine atoms formed within the laser pulse. These results are discussed within the context of solar energy conversion by dye-sensitized solar cells and storage via chemical bond formation.

  • 4.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Flash-Quench Technique Employed To Study the One-Electron Reduction of Triiodide in Acetonitrile: Evidence for a Diiodide Reaction Product2010In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 22, p. 10223-10225Article in journal (Refereed)
    Abstract [en]

    The one-electron reduction of triiodide (I3?) by a reduced ruthenium polypyridyl compound was studied in an acetonitrile solution with the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [RuII(deeb)3]2+ by iodide generated the reduced ruthenium compound [RuII(deeb?)(deeb)2]+ and diiodide (I2??). The subsequent reaction of [RuII(deeb?)(deeb)2]+ with I3? indicated that I2?? was a product that appeared with a second-order rate constant of (5.1 ± 0.2) ? 109 M?1 s?1. After correction for diffusion and some assumptions, Marcus theory predicted a formal potential of ?0.58 V (vs SCE) for the one-electron reduction of I3?. The relevance of this reaction to solar energy conversion is discussed.

  • 5.
    Freys, Jonathan C.
    et al.
    Uppsala University.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    D'Amario, Luca
    Uppsala University.
    Brown, Allison M.
    Uppsala University.
    Hammarström, Leif
    Uppsala University.
    Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 42, p. 13105-13111Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2'-bipyridine-4,4'-dicarboxylic acid)(2)N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb)(2)(NMI-phen)](PF(6))(2)) and tris-(2,2'-bipyridine-4,4'-dicarboxylic acid)(3) ruthenium(ii), [(Ru(dcb)(3))Cl(2)]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb)(2)(NMI-phen)](2+) resulted in long-lived charge separation between reduced [Ru(dcb)(2)(NMI-phen)](2+) and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb)(2)(NMI-phen)](2+), the electron localized on the distal NMI group. In tests with I(3)(-)/I(-) and Co(4,4'-di-tert-butyl-bipyridine)(3)(2+/3+) electrolytes, [Ru(dcb)(2)(NMI-phen)](2+) outperformed [Ru(dcb)(3)](2+) in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.

  • 6.
    Gao, Jiajia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    El-Zohry, Ahmed M.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Trilaksana, Herri
    Flinders Univ S Australia, Flinders Ctr NanoScale Sci & Technol CNST, Adelaide, SA 5042, Australia..
    Gabrielsson, Erik
    Dyenamo AB, Greenhouse Labs, Tekn Ringen 38A, SE-11428 Stockholm, Sweden..
    Leandri, Valentina
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ellis, Hanna
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    D'Amario, Luca
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Safdari, Majid
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Andersson, Gunther
    Flinders Univ S Australia, Flinders Ctr NanoScale Sci & Technol CNST, Adelaide, SA 5042, Australia..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 31, p. 26241-26247Article in journal (Refereed)
    Abstract [en]

    A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.

  • 7.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Abrahamsson, Maria
    Johns Hopkins University.
    Farnum, Byron H.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Visible Light Generation of Iodine Atoms and I-ˆ’I Bonds: Sensitized I-ˆ’ Oxidation and I3-ˆ’ Photodissociation2009In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 44, p. 16206-16214Article in journal (Refereed)
    Abstract [en]

    Direct 355 or 532 nm light excitation of TBAI3, where TBA is tetrabutyl ammonium, in CH3CN at room temperature yields an iodine atom, I?, and an iodine radical anion, I2??. In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I2?? with a rate constant of k = 2.5 ± 0.4 ? 1010 M?1 s?1. The I2?? intermediates are unstable with respect to disproportionation and yield initial reactants, k = 3.3 ± 0.1 ? 109 M?1 s?1. The coordination compound Ru(bpz)2(deeb)(PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(C2H5CO2)2-2,2?-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz)2(deeb)2+ displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with ε = 1.7 ? 104 M?1 cm?1. Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield ? = 0.14, and an excited state lifetime τ = 1.75 ?s from which kr = 8.36 ? 104 s?1 and knr = 5.01 ? 105 s?1 were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of ?2500 cm?1 and a pre-exponential factor of 1010 s?1, assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz)2(deeb)2+ in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 ? 10?5. The MLCT excited state was dynamically quenched by iodide with Ksv = 1.1 ? 105 M?1 and kq = 6.6 ± 0.3 ? 1010 M?1 s?1, a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, ?CE = 0.042 ± 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz?)(bpz)(deeb)]+ and I2??. The coincidence of the rate constants for [Ru(bpz?)(bpz)(deeb)]+ formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I2?? was about a factor of 3 slower than excited state decay, k = 2.4 ± 0.2 ? 1010 M?1 s?1, indicating that I2?? was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I? + I? ? I2??. Charge recombination Ru(bpz?)(bpz)(deeb)+ + I2?? ? Ru(bpz)2(deeb)2+ + 2I? was highly favored, ?Go = ?1.64 eV, and well described by a second-order equal concentration kinetic model, kcr = 2.1 ± 0.3 ? 1010 M?1 s?1.

  • 8.
    Gardner, James M
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Beyler, Maryline
    Uppsala University.
    Karnahl, Michael
    Uppsala University.
    Tschierlei, Stefanie
    Uppsala University.
    Ott, Sascha
    Uppsala University.
    Hammarström, Leif
    Uppsala University.
    Light-Driven Electron Transfer between a Photosensitizer and a Proton-Reducing Catalyst Co-adsorbed to NiO2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 47, p. 19322-19325Article in journal (Refereed)
    Abstract [en]

    While intermolecular hole-hopping along the surface of semiconductors is known, there are no previous examples of electron-hopping between molecules on a surface. Herein, we present the first evidence of electron transfer from the photoreduced sensitizer Coumarin-343 (C343) to complex 1, both bound on the surface of NiO. In solution, 1 has been shown to be a mononuclear Fe-based proton-reducing catalyst. The reduction of 1 is reversible and occurs within 50 ns after excitation of C343. Interfacial recombination between the reduced 1(-) and NiO hole occurs on a 100 µs time scale by non-exponential kinetics. The observed process is the first essential step in the photosensitized generation of H2 from a molecular catalyst in the absence of a sacrificial donor reagent.

  • 9.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Giaimuccio, Jovan M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Evidence for Iodine Atoms as Intermediates in the Dye Sensitized Formation of I-ˆ’I Bonds2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 51, p. 17252-17253Article in journal (Refereed)
    Abstract [en]

    Visible light excitation of [Ru(bpz)2(deeb)](PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(CO2Et)2-2,2?-bipyridine, in acetonitrile solutions with iodide is shown to initiate excited-state electron transfer reactions that yield iodine atoms. The iodine atoms subsequently react with iodide to form the I?I bond in I2??. The resultant Ru(bpz?)(bpz)(deeb)+, I2?? stores ?1.64 eV of free energy and returns cleanly to ground-state products with kcr = (2.1 ± 0.3) ? 1010 M?1 s?1.

  • 10.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Kim, Su
    Johns Hopkins University.
    Searson, Peter C.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Electrodeposition of Nanometer-Sized Ferric Oxide Materials in Colloidal Templates for Conversion of Light to Chemical Energy2011In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2011, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Colloidal crystal templates were prepared by gravitational sedimentation of 0.5 micron polystyrene particles onto fluorine-doped tin oxide (FTO) electrodes. Scanning electron microscopy (SEM) shows that the particles were close packed and examination of successive layers indicated a predominantly face-centered-cubic (fcc) crystal structure where the direction normal to the substrate surface corresponds to the (111) direction. Oxidation of aqueous ferrous solutions resulted in the electrodeposition of ferric oxide into the templates. Removal of the colloidal templates yielded ordered macroporous electrodes (OMEs) that were the inverse structure of the colloidal templates. Current integration during electrodeposition and cross-sectional SEM images revealed that the OMEs were about 2 mu m thick. Comparative X-ray diffraction and infrared studies of the OMEs did not match a known phase of ferric oxide but suggested a mixture of goethite and hematite. The spectroscopic properties of the OMEs were insensitive to heat treatments at 300. C. The OMEs were utilized for photoassisted electrochemical oxidation. A sustained photocurrent was observed from visible light in aqueous photoelectrochemical cells. Analysis of photocurrent action spectra revealed an indirect band gap of 1.85 eV. Addition of formate to the aqueous electrolytes resulted in an approximate doubling of the photocurrent.

  • 11. Hoang, Minh Tam
    et al.
    Pham, Ngoc Duy
    Han, Ji Hun
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Oh, Ilwhan
    Integrated Photoelectrolysis of Water Implemented On Organic Metal Halide Perovskite Photoelectrode2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 19, p. 11904-11909Article in journal (Refereed)
    Abstract [en]

    Herein we report on integrated photoelectrolysis of water employing organic metal halide (OMH) perovskite material. Generic OMH perovskite material and device architecture are highly susceptible to degradation by moisture and water. We found that decomposition of perovskite devices proceeds by water ingress through pinholes in upper layers and is strongly affected by applied bias/light and electrolyte pH. It was also found that a pinhole-free hole transport layer (HTL) could significantly enhance the stability of the perovskite photoelectrode, thereby extending the photoelectrode lifetime to several tens of minutes, which is an unprecedented record-long operation. Furthermore, a carbon nanotube (CNT)/polymer composite layer was developed that can effectively protect the underlying perovskite layer from electrolyte molecules.

  • 12.
    Karlsson, Mattias E.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Mamie, Yann C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Calamida, Andrea
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Pourrahimi, Amir Masoud
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 17, p. 5079-5087Article in journal (Refereed)
    Abstract [en]

    A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.

  • 13.
    Leandri, V.
    et al.
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden..
    Yang, W.
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden.;Imperial Coll London, Dept Chem, London SW7 2AZ, England..
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Boschloo, G.
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden..
    Ott, S.
    Uppsala Univ, Dept Chem, Angstrom Lab, S-75120 Uppsala, Sweden..
    Rapid Microwave-Assisted Self-Assembly of a Carboxylic-Acid-Terminated Dye on a TiO2 Photoanode2018In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 1, no 1, p. 202-210Article in journal (Refereed)
    Abstract [en]

    Self-assembly of carboxylic-acid-functionalized dyes on mesoporous, anatase TiO2 is at the heart of dye-sensitized solar cells (DSSCs). However, the process often requires 6-20 h of electrode immersion at room temperature in the dye-bath solutions. Here, we introduce a new, rapid microwave-assisted sensitization technique (MINAS), which significantly accelerates the sensitization process and yields high-quality, self-assembled films of an organic dye within 5 min. Targeted experiments show that the effects of the microwave radiation cannot be explained purely on the basis of the thermal component. The interaction of the microwave radiation with the conductive fluorine-doped tin oxide (FTO) electrical contact is a key aspect to consider and a unique feature of MWAS that is the likely cause for producing rapid self-assembly of the dye on the surface.

  • 14.
    Leandri, Valentina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Coumarin as a Quantitative Probe for Hydroxyl Radical Formation in Heterogeneous Photocatalysis2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 11, p. 6667-6674Article in journal (Refereed)
    Abstract [en]

    In this work, we have assessed coumarin as a quantitative probe for hydroxyl radical formation in heterogeneous photocatalysis. Upon reaction with the hydroxyl radical, coumarin produces several hydroxylated products, of which one, 7-OH-coumarin, is strongly fluorescent. The fluorescence emission is strongly affected by inner filtering due to the presence of coumarin. Therefore, we performed a series of calibration experiments to correct for the coumarin concentration. From the calibration experiments, we could verify that the inner-filtering effect can be attributed to the competing absorption of the fluorescence excitation light between coumarin and 7-OH-coumarin. Through judicious calibration for the inner-filtering effects, the corrected results for the photocatalytic system show that the rate of hydroxyl scavenging is constant with time for initial coumarin concentrations of ≥50 μM under the conditions of our experiments. The rate increases linearly with coumarin concentration, as expected from the Langmuir–Hinshelwood model. Within the coumarin concentration range used here, the photocatalyst surface does not become saturated. Given the fact that the highest coumarin concentration used (1 mM) in this work is quite close to the solubility limit, we conclude that coumarin cannot be used to assess the full photocatalytic capacity of the system, i.e., surface saturation is never reached. The rate of hydroxyl radical scavenging will, to a large extent, depend on the affinity to the surface, and it is therefore not advisable to use coumarin as a probe for photocatalytic efficiency when comparing different photocatalysts.

  • 15.
    Leandri, Valentina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Reply to "Comment on 'Coumarin as a Quantitative Probe for Hydroxyl Radical Formation in Heterogeneous Photocatalysis'"2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 33, p. 20685-20686Article in journal (Other academic)
  • 16.
    Leandri, Valentina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Liu, Peng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sadollahkhani, Azar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Safdari, Majid
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Excited-State Dynamics of [Ru(bpy)(3)](2+) Thin Films on Sensitized TiO2 and ZrO22019In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 20, no 4, p. 618-626Article in journal (Refereed)
    Abstract [en]

    The excited state dynamics of Tris(2,2 '-bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)(3)(PF6)(2)], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern-Volmer plot of LEG4-sensitized TiO2 substrates with a spin-coated [Ru(bpy)(3)(PF6)(2)] layer on top shows considerable quenching of the emission of the latter. Interestingly, time-resolved emission spectroscopy reveals the presence of a fast-decay time component (25 +/- 5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)(3)(PF6)(2)] ground state into the oxidized sensitizer. Therefore, we speculate that the fast-decay time component observed stems from excited-state electron transfer from [Ru(bpy)(3)(PF6)(2)] to the oxidized sensitizer. Solid-state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)(3)(PF6)(2)] as a hole-transporting material (HTM), exhibit 1.2 % and 1.1 % power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited-state electron transfer.

  • 17.
    Leandri, Valentina
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Pizzichetti, Angela Raffaella Pia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    Uppsala Univ, Angstrom Lab, Dept Chem, Div Phys Chem,Ctr Mol Devices, Box 523, SE-75120 Uppsala, Sweden..
    Franchi, Daniele
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Wei
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Benesperi, Iacopo
    Uppsala Univ, Angstrom Lab, Dept Chem, Div Phys Chem,Ctr Mol Devices, Box 523, SE-75120 Uppsala, Sweden..
    Freitag, Marina
    Uppsala Univ, Angstrom Lab, Dept Chem, Div Phys Chem,Ctr Mol Devices, Box 523, SE-75120 Uppsala, Sweden..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. DUT, DUT KTH Joint Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Exploring the Optical and Electrochemical Properties of Homoleptic versus Heteroleptic Diimine Copper(I) Complexes2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 18, p. 12167-12177Article in journal (Refereed)
    Abstract [en]

    Due to ligand scrambling, the synthesis and investigation of the properties of heteroleptic Cu(I) complexes can be a challenging task. In this work, we have studied the optical and electrochemical properties of a series of homoleptic complexes, such as [Cu(dbda)(2)](+), [Cu(dmp)(2)](+), [Cu(Br-dmp)(2)](+), [Cu(bcp)(2)](+), [Cu(dsbtmp)(2)](+), [Cu(biq)(2)](+), and [Cu(dap)(2)](+) in solution, and those of their heteroleptics [Cu(dbda)(dmp)](+), [Cu(dbda)(Br-dmp)](+), [Cu(dbda)(bcp)](+), [Cu(dbda)(dsbtmp))(+), [Cu(dbda)(biq)](+), [Cu(dbda)(dap)](+) adsorbed on the surface of anatase TiO2 (dbda = 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid; dmp = 2,9-dimethyl-1,10-phenanthroline; Br-dmp = 5-bromo 2,9-dimethyl-1,10-phenanthroline; bcp = bathocuproine or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline; biq = 2,2'-biquinoline; dap = 2,9-dianisyl-1,10-phenanthroline). We show that the maximum absorption wavelengths of the heteroleptic complexes on TiO2 can be reasonably predicted from those of the homoleptic complexes in solution through a simple linear relation, whereas the prediction of their redox properties is less trivial. In the latter case, two different linear patterns emerge: one including the ligands bcp, biq, and dap and another one including the ligands dmp, Br-dmp, and dsbtmp. We offer an interpretation of the data based on the chemical structure of the ligands. On one hand, ligands bcp, biq, and dap possess a more extended pi-conjugated system, which gives a more prominent contribution to the overall redox properties of the ligand dbda. On the other hand, the ligands dmp, Br-dmp, and dsbtmp are all phenanthroline-based containing alkyl substituents and contribute less than dbda to the overall redox properties.

  • 18.
    Lissau, Jonas Sandby
    et al.
    Uppsala University.
    Gardner, James M.
    Uppsala University.
    Morandeira, Ana
    Uppsala University.
    Photon Upconversion on Dye-Sensitized Nanostructured ZrO2 Films2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 46, p. 23226-23232Article in journal (Refereed)
    Abstract [en]

    Photon upconversion based on sensitized triplet?triplet annihilation has been observed on nanocrystalline ZrO2 films cosensitized with platinum(II) octaethylporphyrin (triplet sensitizer) and 9,10-diphenylanthracene (singlet emitter) under sunlight-like conditions (noncoherent excitation source, excitation light intensity as low as 5 mW/cm2). Time-resolved emission measurements showed a fast rise of the upconverted signal (≀10 ns), suggesting that triplet energy migration most probably occurs through a ?static? Dexter mechanism. To the best of our knowledge, this is the first observation of photon upconversion based on sensitized triplet?triplet annihilation on a sensitized mesoporous metal oxide. Implementation of similar systems in dye-sensitized solar cells would increase the maximum theoretical efficiency of these devices from 30% to over 40%.

  • 19. Lissau, Jonas Sandby
    et al.
    Nauroozi, Djawed
    Santoni, Marie-Pierre
    Edvinsson, Tomas
    Ott, Sascha
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Morandeira, Ana
    What Limits Photon Upconversion on Mesoporous Thin Films Sensitized by Solution-Phase Absorbers?2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 9, p. 4550-4564Article in journal (Refereed)
    Abstract [en]

    Photon upconversion by sensitized triplet-triplet annihilation (UC-STTA) is a promising strategy for breaking the Shockley-Queisser limit for efficiency of single-threshold solar cells, and in particular dye-sensitized solar cells (DSSCs). Here, we report on a heterogeneous UC system, where the annihilating dyes (emitters) are bound to a ZrO2 nanostructured film and the light absorbing dyes (sensitizers) are free in solution. A comparative study of four different emitter dyes was conducted, all of them derivatives of the well-known UC-STTA emitter dye 9,10-diphenylanthracene (DPA), and in every case, the sensitizer dye was platinum(II) octaethylporphyrin (PtOEP). The physical separation of emitter and sensitizer molecules in two different phases makes homogeneous triplet-triplet annihilation among sensitizers in solution a significant loss channel at high excitation intensity and low emitter surface coverage. For the studied emitter dyes, the number and type of anchor groups, and the solubility of the emitter dye in the employed solvents, are the determining factors of the UC output. The signal evolves in time and with light exposure due to emitter desorption and light-induced endoperoxide formation. These results can guide the way toward a better understanding of UC-STTA on nanocrystalline metal oxides and its development for solar energy applications.

  • 20. Lissau, Jonas Sandby
    et al.
    Nauroozi, Djawed
    Santoni, Marie-Pierre
    Ott, Sascha
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Morandeira, Ana
    Anchoring Energy Acceptors to Nanostructured ZrO2 Enhances Photon Upconversion by Sensitized Triplet-Triplet Annihilation Under Simulated Solar Flux2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 28, p. 14493-14501Article in journal (Refereed)
    Abstract [en]

    Photon upconversion by sensitized triplet-triplet annihilation (UC-STTA) is a promising strategy for boosting the theoretical maximum efficiency of single threshold solar cells, in particular, dye-sensitized solar cells (DSSCs). Here, we report a substantial increase in the efficiency of UC-STTA on a nanostructured surface, using noncoherent excitation light with intensities as low as 0.5 mW cm(-2), easily achieved under sun illumination. The studied surface was a mesoporous ZrO2 film working as a proxy system for the study of photophysics relevant to DSSCs. A well-known UC-STTA "emitter" dye, 9,10-diphenylanthracene (DPA), was chemically modified to yield methyl 4-(10-p-tolylanthracen-9-yl)benzoate (MTAB), which was chemisorbed onto ZrO2. The "sensitizer" dye, platinum(II) octaethylporphyrin (PtOEP), was free in butyronitrile (BuN) solution surrounding the ZrO2 nanostructure. A rigorous oxygen removal minimized photodegradation of the dyes and enhanced triplet-triplet annihilation efficiency. The system already approaches the so-called "strong annihilation limit" at light intensities below 8 mW cm(-2). Highly efficient triplet-triplet annihilation is a requisite for the use of UC-STTA in DSSCs. Time-resolved data show that the limiting process in the UC-STTA mechanism of the present system is the dynamic triplet energy transfer step from PtOEP in solution to MTAB on the surface of ZrO2. This result can guide the way toward a better understanding and further efficiency improvement of UC-STTA on nanocrystalline metal oxides.

  • 21.
    Lissau, Jonas Sandby
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Uppsala University, Sweden.
    Nauroozi, Djawed
    Santoni, Marie-Pierre
    Ott, Sascha
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Morandeira, Ana
    Photon Upconversion from Chemically Bound Triplet Sensitizers and Emitters on Mesoporous ZrO2: Implications for Solar Energy Conversion2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 46, p. 25792-25806Article in journal (Refereed)
    Abstract [en]

    Photon upconversion by sensitized triplet-triplet annihilation (UC-STTA) is studied in systems with triplet sensitizers and emitter molecules cochemisorbed onto nanostructured ZrO2 films. UC-STTA is a promising strategy to overcome the Shockley-Queisser efficiency limit of single-threshold solar cells. The dye-loaded mesoporous ZrO2 films studied herein allow high molecular densities and are good proxy systems for the study of photophysics relevant to dye-sensitized solar cells. Two sensitizer/emitter dye pairs are studied: platinum(II) deuteroporphyrin IX dicarboxylic acid/4,4'-(10-(anthracene-9,10-diyl)dibenzoic acid and platinum(II) deuteroporphyrin IX dimethyl ester/methyl 4-(10-(p-tolyl)anthracen-9-yl)benzoate. Both dye pairs are closely related to the standard UC-STTA molecular pair platinum(II) octaethylporphyrin (PtOEP)/9,10-diphenylanthracene (DPA). By chemically anchoring the upconverting dye pairs onto ZrO2 films a significant improvement in UC-STTA efficiency is achieved with respect to previously studied cophysisorbed PtOEP/DPA. Controlled variation of the sensitizer/emitter dye ratios onto the surface shows that new energy loss mechanisms appear at high sensitizer surface coverage. Spectral signatures of porphyrin aggregates suggest separate sensitizer domains form, which limits the triplet sensitization of emitter molecules. The nanosecond time scale rise and decay of the observed UC emission are likely linked to the sample stability over time; UC emission is observed 1 year after sample preparation. These are promising properties for the application of this type of system for solar energy conversion.

  • 22.
    Liu, Jianhua
    et al.
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Jia, Donglin
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala Univ, Dept Chem Angstrom, Phys Chem, S-75120 Uppsala, Sweden..
    Zhang, Xiaoliang
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Metal nanowire networks: Recent advances and challenges for new generation photovoltaics2019In: MATERIALS TODAY ENERGY, ISSN 2468-6069, Vol. 13, p. 152-185Article, review/survey (Refereed)
    Abstract [en]

    Transparent conducting electrodes which allow photons passing through and simultaneously transfers the charge carriers are critical for the construction of high-performance photovoltaic cells. Electrodes based on metal oxides, such as indium-doped tin oxide (ITO) or fluorine-doped tin oxide (FTO), may have limited application in new generation flexible solar cells, which employ solution-processed roll-to-roll or ink-printing techniques toward large-area-fabrication approach, due to their brittleness and poor mechanical properties. Metal nanowire network (MNWN) emerges as a highly potential alternative candidate instead of ITO or FTO due to the high transparency, low sheet resistance, low cost, solution processable and compatibility with a flexible substrate for high throughput production. This feature article systematically summarizes the recent advances of the MNWNs, including new concepts and emerging strategies for the synthesis of metal nanowires (MNWs), various approaches for the preparation of MNWNs and comprehensively discusses the novel MNWN electrodes prepared on different substrates. The state-of-the-art new generation solar cell devices, such as transparent, flexible and light-weight solar cells, with MNWN as a transparent conductive electrode are emphasized. Finally, the opportunities and challenges for the development of MNWN electrodes toward application in the new generations of photovoltaic devices are discussed.

  • 23.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Solution processable, cross-linked sulfur polymers as solid electrolytes in dye-sensitized solar cells2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 78, p. 14660-14662Article in journal (Refereed)
    Abstract [en]

    Inverse-vulcanized polymeric sulfur has been prepared and utilized for solid-state dye sensitized solar cells. A power conversion efficiency of 1.5% was recorded with a short-circuit current of 4.1 mA cm-2 and an open-circuit voltage of 0.75 V under standard AM 1.5G illumination (1000 W m-2). The results in the present study qualify the new polymeric sulfur material as a future candidate as low-cost, hole-transport material for solid-state dye-sensitized solar cells.

  • 24.
    Phuyal, Dibya
    et al.
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Safdari, Majid
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Pazoki, Meysam
    Uppsala Univ, Dept Engn Sci, Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Liu, Peng
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Philippe, Bertrand
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Kyashnina, Kristina O.
    ESRF, Rossendorf Beamline, CS40220, F-38043 Grenoble 9, France.;HZDR, Inst Resource Ecol, POB 510119, D-01314 Dresden, Germany..
    Karis, Olof
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Butorin, Sergei M.
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Rensmo, Hakan
    Uppsala Univ, Dept Phys & Astron, Solid State Phys, Angstrom Lab, Box 516, SE-75121 Uppsala, Sweden..
    Edvinsson, Tomas
    Uppsala Univ, Dept Engn Sci, Solid State Phys, Angstrom Lab, SE-75121 Uppsala, Sweden..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study2018In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 15, p. 4959-4967Article in journal (Refereed)
    Abstract [en]

    Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

  • 25.
    Sadollahkhani, Azar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Leandri, Valentina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Safdari, Majid
    KTH.
    Zhang, Wei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Energetic Barriers to Interfacial Charge Transfer and Ion Movement in Perovskite Solar Cells2017In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 18, no 21, p. 3047-3055Article in journal (Refereed)
    Abstract [en]

    Highly efficient perovskite solar cells have been characterized by current-density/voltage measurements in the dark at varied scan rates. The results were compared to the solar cells without a hole-transporting layer to investigate the role of ultrathin hole-transporting layers in solar-cell function. The parameters of internal voltage, diode ideality factor, capacitive current, and capacitance were calculated from the current-density/voltage response of the cells in the dark. The results show that the absence of the hole-transporting layer can cause a large recombination current within the depletion region at the gold contact/perovskite interface, and thus affects the cell performance.

  • 26.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fischer, Andreas C.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Erratum to: Structure and function relationships in alkylammonium lead(II) iodide solar cells2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 17, p. 9317-9317Article in journal (Refereed)
  • 27.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fischer, Andreas
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Spectroscopic Material Characterization of Organic Lead Halide MaterialsManuscript (preprint) (Other academic)
  • 28.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fischer, Andreas I.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Structure and function relationships in alkylammonium lead(II) iodide solar cells2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 17, p. 9201-9207Article in journal (Refereed)
    Abstract [en]

    Alkylammonium lead(ii) iodide materials (APbI<inf>3</inf>), based on the general formula of CH<inf>3</inf>-(CH<inf>2</inf>)<inf>n</inf>-NH<inf>3</inf>PbI<inf>3</inf>, may lead to a monumental leap in developing affordable photovoltaics. Herein, we correlate the structure and function relationships of alkylammonium lead(ii) iodide in solar cells. We investigated changes in the structure of APbI<inf>3</inf> materials by varying the alkylammonium cations in their structure. As the size of the alkylammonium cation increased, the crystallographic unit cell increased in size and yielded lower symmetry crystals. High symmetry materials, those with cubic symmetry, showed the highest conductivity, the smallest bandgap, and produced the best performing solar cells. Structural changes were investigated by X-ray crystallography, X-ray powder diffraction, and Raman scattering.

  • 29.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Uppsala University, Sweden.
    Lohse, Peter W.
    Häggman, Leif
    Frykstrand, Sara
    Högberg, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Asencio, Ruben Alvarez
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. IMDEA Nanoscience, Spain.
    Gardner, James
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hagfeldt, Anders
    Boschloo, Gerrit
    Investigation of cobalt redox mediators and effects of TiO2 film topology in dye-sensitized solar cells2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 61, p. 56580-56588Article in journal (Refereed)
    Abstract [en]

    One-electron outer-sphere redox couples, such as cobalt metal-organic complexes, represent an interesting alternative as redox mediators in dye-sensitized solar cells since they show weak visible light absorption and available redox potentials may lead to higher open circuit voltage values. Here, we have studied the effect of using different substituents on bipyridyl and phenanthroline ligands in cobalt redox shuttles, giving the following complexes: Co[tris(4,4'-dimethoxy-2,2'-bipyridine)(PF6)(2)], Co[tris(4,4'-dichloro-2,2'-bipyridine)(PF6)(2)] and Co[tris(4,7-dichloro-1,10-phenanthroline)(CF3SO3)(2)], displaying a range of CoII/CoIII redox potentials from +0.37 to +0.79 V vs. NHE. The regeneration kinetics of the organic dye D35 was found to depend systematically on the redox mediator potential, which was explained using Marcus theory. The mass transport of cobalt mediators in dye-sensitized solar cells is highly dependent on the porosity, effective surface area and roughness of the mesoporous TiO2 films. Therefore, films with different TiO2 pore sizes were prepared and investigated to gain an insight into the topological effects of TiO2 film preparation in order to obtain optimum solar cell performance.

  • 30.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Phuyal, Dibya
    Liu, Ping
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Philippe, Bertrand
    Kvashnina, Kristina O.
    Butorin, Sergei M.
    Rensmo, Håkan
    Karis, Olof
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Electronic structure of 2D Lead (II) Iodide Perovskites: An Experimental and Theoretical StudyManuscript (preprint) (Other academic)
  • 31.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Phuyal, Dibya
    Philippe, Bertrand
    Svensson, Per H.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. SP Process Development, Sweden .
    Butorin, Sergei M.
    Kvashnina, Kristina O.
    Rensmo, Håkan
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Impact of Synthetic Route on Structural and Physical Properties of Butyl-1,4-Diammonium Lead Iodide Semiconductors2017In: Journal of Materials Chemistry A, ISSN 2050-7488Article in journal (Refereed)
  • 32.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Svensson, Per H.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. SP Process Development, Sweden.
    Hoang, Minh Tam
    Oh, Ilwhan
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Layered 2D alkyldiammonium lead iodide perovskites: synthesis, characterization, and use in solar cells2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 40, p. 15638-15646Article in journal (Refereed)
    Abstract [en]

    The synthetic route and properties of three 2D hybrid organic/inorganic lead iodide perovskite materials are reported. The 2D perovskites were synthesized from the reaction between PbI2 and the di-cations of 1,4-diaminobutane, 1,6-diaminohexane, and 1,8-diaminooctane. The resulting products were [NH3(CH2)(4)NH3] PbI4 (BdAPbI(4)), [NH3(CH2)(6)NH3]PbI4 (HdAPbI(4)), and [NH3(CH2)(8)NH3]PbI4 (OdAPbI(4)). Structural characterization shows that two dimensional perovskite structures were formed with inorganic structural planes separated by organic layers. Absorption spectra show band gaps of 2.37 eV (BdAPbI(4)), 2.44 eV (HdAPbI(4)), and 2.55 eV (OdAPbI(4)). The 2D perovskite materials were investigated as light absorbing materials in solid state solar cells. The best performing material under moist, ambient conditions was BdAPbI4 (1.08% efficiency), which was comparable to methylammonium Pb(II) iodide (MAPbI(3)) solar cells (2.1% efficiency) manufactured and studied under analogous conditions. When compared to MAPbI(3), the 2D materials have larger band gaps and lower photoconductivity, while BdAPbI(4) based solar cells shows a comparable absorbed photon-to-current efficiency as compared to MAPbI(3) based ones.

  • 33.
    Tian, Haining
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Oscarsson, Johan
    Gabrielsson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Eriksson, Susanna K.
    Lindblad, Rebecka
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Hao, Yan
    Boschloo, Gerrit
    Johansson, Erik M. J.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hagfeldt, Anders
    Rensmo, Håkan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 4282-Article in journal (Refereed)
    Abstract [en]

    Supramolecular interactions based on porphyrin and fullerene derivatives were successfully adopted to improve the photovoltaic performance of p-type dye-sensitized solar cells (DSCs). Photoelectron spectroscopy (PES) measurements suggest a change in binding configuration of ZnTCPP after co-sensitization with C60PPy, which could be ascribed to supramolecular interaction between ZnTCPP and C60PPy. The performance of the ZnTCPP/C60PPy-based p-type DSC has been increased by a factor of 4 in comparison with the DSC with the ZnTCPP alone. At 560 nm, the IPCE value of DSCs based on ZnTCPP/C60PPy was a factor of 10 greater than that generated by ZnTCPP-based DSCs. The influence of different electrolytes on charge extraction and electron lifetime was investigated and showed that the enhanced V-oc from the Co2+/(3+)(dtbp)(3)-based device is due to the positive E-F shift of NiO.

  • 34.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gabrielsson, Erik
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    1,1,2,2-Tetrachloroethane (TeCA) as a Solvent Additive for Organic Hole Transport Materials and Its Application in Highly Efficient Solid-State Dye-Sensitized Solar Cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 10, article id 1402340Article in journal (Refereed)
    Abstract [en]

    A low-cost, chlorinated hydrocarbon solvent, 1,1,2,2-tetrachloroethane (TeCA), is used as an effective additive for the triarylamine-based organic hole-transport material, Spiro-OMeTAD, which is successfully applied in highly efficient solid-state dye-sensitized solar cells. A record power conversion efficiency of 7.7% is obtained by using the donor (D)-π-acceptor (A)-dye, LEG4, in combination with the new method of TeCA-doping of the hole-transporting material Spiro-OMeTAD.

  • 35.
    Zhang, Fuguo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Yao, Zhaoyang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Guo, Yaxiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Bergstrand, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Brett, Calvin
    Cai, Bin
    State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT−KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology (DUT), 116024 Dalian, China.
    Hajian, Alireza
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Yang, X.
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, Superseded Departments (pre-2005), Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Polymeric, Cost-Effective, Dopant-Free Hole Transport Materials for Efficient and Stable Perovskite Solar Cells2019In: Journal of the American Chemical Society, Vol. 141, no 50, p. 19700-19707Article in journal (Refereed)
    Abstract [en]

    Perovskite solar cells (PSCs) has skyrocketed in the past decade to an unprecedented level due to their outstanding photoelectric properties and facile processability. However, the utilization of expensive hole transport materials (HTMs) and the inevitable instability instigated by the deliquescent dopants represent major concerns hindering further commercialization. Here, a series of low-cost, conjugated polymers are designed and applied as dopant-free HTMs in PSCs, featuring tuned energy levels, good temperature and humidity resistivity, and excellent photoelectric properties. Further studies highlight the critical and multifaceted roles of the polymers with respect to facilitating charge separation, passivating the surface trap sites of perovskite materials, and guaranteeing long-term stability of the devices. A stabilized power conversion efficiency (PCE) of 20.3% and remarkably enhanced device longevity are achieved using the dopant-free polymer P3 with a low concentration of 5 mg/mL, qualifying the device as one of the best PSC systems constructed on the basis of dopant-free HTMs so far. In addition, the flexible PSCs based on P3 also exhibit a PCE of 16.2%. This work demonstrates a promising route toward commercially viable, stable, and efficient PSCs.

  • 36.
    Zhang, Wei
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Hua, Yong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhang, Biaobiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Liu, Peng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Leandri, Valentina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Guo, Yu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Chen, Hong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol DUT, DUT KTH Joint Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Kloo, Lars
    The Central Role of Ligand Conjugation for Properties of Coordination Complexes as Hole-Transport Materials in Perovskite Solar Cells2019In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 9, p. 6768-6779Article in journal (Refereed)
    Abstract [en]

    Two zinc-based coordination complexes Y3 and Y4 have been synthesized and characterized, and their performance as hole-transport materials (HTMs) for perovskite solar cells (PSCs) has been investigated. The complex Y3 contains two separate ligands, and the molecular structure can be seen as a disconnected porphyrin ring. On the other hand, Y4 consists of a porphyrin core and therefore is a more extended conjugated system as compared to Y3. The optical and redox properties of the two different molecular complexes are comparable. However, the hole mobility and conductivity of Y4 as macroscopic material are remarkably higher than that of Y3. Furthermore, when employed as hole-transport materials in perovskite solar cells, cells containing Y4 show a power conversion efficiency (PCE) of 16.05%, comparable to the Spiro-OMeTAD-based solar cells with an efficiency around 17.08%. In contrast, solar cells based on Y3 show a negligible efficiency of about 0.01%. The difference in performance of Y3 and Y4 is analyzed and can be attributed to the difference in packing of the nonplanar and planar building blocks in the corresponding materials.

  • 37.
    Zhang, Wei
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Sadollahkhani, Azar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Leandri, Valentina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Mechanistic Insights from Functional Group Exchange Surface Passivation: A Combined Theoretical and Experimental Study2019In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 4, p. 2723-2733Article in journal (Refereed)
    Abstract [en]

    Four different functional groups including amino (-NH2), phosphine (-PH2), hydroxyl (-OH), and thiol (-SH) were combined with POSS (polyhedral oligomeric silsesquioxane) molecules to investigate how functional groups affect the surface passivation of POSS systems. Results from density-functional theory (DFT) calculations indicate that functional group amino (-NH2) with adsorption energy 86 (56) kJ mol(-1) is consistently better than that of thiol (-SH) with adsorption energy 68 (43) kJ mor(-1) for different passivation mechanisms. Theoretical studies on the analogous POSS-OH and POSS-PH2 systems show similar adsorption energies. Two of the systems were also investigated experimentally; aminopropyl isobutyl POSS (POSS-NH2) and mercaptopropyl isobutyl POSS (POSS-SH) were applied as passivation materials for MAPbI(3) (MA = methylammonium) perovskite and (FA)(0.85)(MA)(0.15)Pb(I-3)(0.85)(Br-3)(0)(.15)(FA = formamidinium) perovskite films. The same conclusion was drawn based on the results from contact angle studies, X-ray diffraction (XRD), and the stability of solar cells in ambient atmosphere, indicating the vital importance of choice of functional groups for passivation of the perovskite materials.

  • 38.
    Zhang, Wei
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Guo, Yu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Zhang, Biaobiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Leandri, Valentina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Xu, Bo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Li, Zhuofeng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Gardner, James M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Single crystal structure and opto-electronic properties of oxidized Spiro-OMeTAD2020In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 56, no 10, p. 1589-1592Article in journal (Refereed)
    Abstract [en]

    Single crystals of Spiro(TFSI)2 were grown, the optical and electronic properties were characterized and compared with neutral Spiro-OMeTAD. Density-functional theory was used to get insights into binding and band structure properties. The flat valence bands indicate a rather limited orbital overlap in Spiro(TFSI)2.

1 - 38 of 38
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