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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. Chen, Cheng
    et al.
    Zhang, Wei
    Cong, Jiayan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Cheng, Ming
    Zhang, Biaobiao
    Chen, Hong
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Li, Ruifeng
    Safdari, Majid
    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.
    Sun, Licheng
    Cu(II) Complexes as p-Type Dopants in Efficient Perovskite Solar Cells2017In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 2, no 2, p. 497-503Article in journal (Refereed)
    Abstract [en]

    In this work, two Cu(II) complex compounds are designed and synthesized for applications as p-type dopants in solid-state perovskite solar cells (PSCs). Through the characterization of the optical and electrochemical properties, the complex Cu(bpcm)(2) is shown to be eligible for oxidization of the commonly used hole-transport material (HTM) SpiroOMeTAD. The reason is the electron-withdrawing effect of the chloride groups on the ligands. When the complex was applied as p-type dopant in PSCs containing Spiro-OMeTAD as HTM, an efficiency as high as 18.5% was achieved. This is the first time a Cu(II) pyridine complex has been used as p-type dopant in PSCs.

  • 3.
    Cheng, Ming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Chen, Cheng
    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), 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.
    Efficient Perovskite Solar Cells Based on a Solution Processable Nickel(II) Phthalocyanine and Vanadium Oxide Integrated Hole Transport Layer2017In: Advanced Energy Materials, ISSN 1614-6832, Vol. 7, no 14, article id 1602556Article in journal (Refereed)
    Abstract [en]

    An organic-inorganic integrated hole transport layer (HTL) composed of the solution-processable nickel phthalocyanine (NiPc) abbreviated NiPc-(OBu)(8) and vanadium(V) oxide (V2O5) is successfully incorporated into structured mesoporous perovskite solar cells (PSCs). The optimized PSCs show the highest stabilized power conversion efficiency of up to 16.8% and good stability under dark ambient conditions. These results highlight the potential application of organic-inorganic integrated HTLs in PSCs.

  • 4.
    Cong, Jiayan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Kinschel, Dominik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Dyenamo AB, Sweden.
    Daniel, Quentin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gabrielsson, E.
    Chen, Hong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Svensson, Per H.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. SP Process Development Forskargatan, Sweden.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Bis(1,1-bis(2-pyridyl)ethane)copper(i/II) as an efficient redox couple for liquid dye-sensitized solar cells2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 38, p. 14550-14554Article in journal (Refereed)
    Abstract [en]

    A new redox couple, [Cu(bpye)2]+/2+, has been synthesized, and applied in dye-sensitized solar cells (DSSCs). Overall efficiencies of 9.0% at 1 sun and 9.9% at 0.5 sun were obtained, which are considerably higher than those obtained for cells containing the reference redox couple, [Co(bpy)3]2+/3+. These results represent a record for copper-based complex redox systems in liquid DSSCs. Fast dye regeneration, sluggish recombination loss processes, faster electron self-exchange reactions and suitable redox potentials are the main reasons for the observed increase in efficiency. In particular, the main disadvantage of cobalt complex-based redox couples, charge-transport problems, appears to be resolved by a change to copper complex redox couples. The results make copper complex-based redox couples very promising for further development of highly efficient DSSCs.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Chemical Structure and Physical Properties of Organic-Inorganic Metal Halide Materials for Solid State Solar Cells2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Abstract

    Methylammonium lead (II) iodide has recently attracted considerable interest which may lead to substantial developments of efficient and inexpensive industrial photovoltaics. The application of this material as a light-absorbing layer in solid-state solar cells leads to impressive efficiency of over 22% in laboratory devices. However, for industrial applications, fundamental issues regarding their thermal and moisture stability need to be addressed. MAPbI3 belongs to the perovskite family of materials with the general formula ABX3 ,where is the organic cation (methylammonium) which is reported to be a major source of instability. In this work, a variety of alkyammonium lead (II) iodide materials have been synthesized by changing the organic cation, to study the relationship between the structural and physical properties of these materials. [(A)PbI3] and (A)PbI4 series were studied. Three dimensional (3D) networks (MAPbI3,MAPbBr3), two dimensional (2D) layered systems (BdAPbI4, HdAPbI4, OdAPbI4), and one dimensional (1D) columns (EAPbI3, PAPbI3, EAPb2I6) were found for the materials. [PbI6] octahedral structural units were repeated through the material network depending on the dimensionality and connectivity of the materials. Where a bulkier cation was introduced, the crystallographic unit cell increased in size which resulted in lower symmetry crystals. The connectivity of the unit cells along the material networks was found to be based on corner-sharing and face-sharing. Lower dimensionality resulted in larger bandgaps and lower photoconductivity, and hence a lower light conversion efficiency for the related solar cells. The thermal and moisture stability was greater in the 1D and 2D materials with bulkier organic cations than with methylammonium.

    In total, an overview is provided of the relationship between the chemical dimensionality and physical properties of the organic-inorganic lead halide materials with focus on the solar cell application.

  • 10.
    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)
  • 11.
    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)
  • 12.
    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.

  • 13.
    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.

  • 14.
    Safdari, Majid
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Phuyal, D.
    Philippe, B.
    Svensson, Per H.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. SP Process Development, Sweden.
    Butorin, S. M.
    Kvashnina, K. O.
    Rensmo, H.
    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 routes on the structural and physical properties of butyl-1,4-diammonium lead iodide semiconductors2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 23, p. 11730-11738Article in journal (Refereed)
    Abstract [en]

    We report the significant role of synthetic routes and the importance of solvents in the synthesis of organic-inorganic lead iodide materials. Through one route, the intercalation of dimethylformamide in the crystal structure was observed leading to a one-dimensional (1D) [NH3(CH2)4NH3]Pb2I6 structure of the product. This product was compared with the two-dimensional (2D) [NH3(CH2)4NH3]PbI4 recovered from aqueous solvent based synthesis with the same precursors. UV-visible absorption spectroscopy showed a red-shift of 0.1 eV for the band gap of the 1D network in relation to the 2D system. This shift primarily originates from a shift in the valence band edge as determined from photoelectron-and X-ray spectroscopy results. These findings also suggest the iodide 5p orbital as the principal component in the density of states in the valence band edge. Single crystal data show a change in the local coordination around iodide, while in both materials, lead atoms are surrounded by iodide atoms in octahedral units. The conductivity of the one-dimensional material ([NH3(CH2)4NH3]Pb2I6) was 50% of the two-dimensional material ([NH3(CH2)4NH3]PbI4). The fabricated solar cells reflect these changes in the chemical and electronic structure of both materials, although the total light conversion efficiencies of solar cells based on both products were similar.

  • 15.
    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)
  • 16.
    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)
  • 17.
    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.

  • 18. Shmyreva, Anna A.
    et al.
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 22, article id 224201Article in journal (Refereed)
    Abstract [en]

    Orders of magnitude decrease of Pb-207 and Hg-199 NMR longitudinal relaxation times T-1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(II) halides, the most dramatic decrease of T-1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time. Published by AIP Publishing.

  • 19.
    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.

  • 20.
    Zhang, Wei
    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.
    Sadollahkhani, Azar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhang, Biaobiao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Fuguo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hao, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hua, Yong
    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.
    Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells2017In: ACS OMEGA, ISSN 2470-1343, Vol. 2, no 12, p. 9231-9240Article in journal (Refereed)
    Abstract [en]

    Triphenylamine-based metal complexes were designed and synthesized via coordination to Ni(II), Cu(II), and Zn(II) using their respective acetate salts as the starting materials. The resulting metal complexes exhibit more negative energy levels (vs vacuum) as compared to 2,2', 7,7'-tetrakis(N, N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), high hole extraction efficiency, but low hole mobilities and conductivities. Application of dopants typically used for Spiro-OMeTAD was not successful, indicating a more complicated mechanism of partial oxidation besides the redox potential. However, utilization as hole-transport material was successful, giving a highest efficiency of 11.1% under AM 1.5G solar illumination.

1 - 20 of 20
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