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Leandri, V., Liu, P., Sadollahkhani, A., Safdari, M., Kloo, L. & Gardner, J. M. (2019). Excited-State Dynamics of [Ru(bpy)(3)](2+) Thin Films on Sensitized TiO2 and ZrO2. ChemPhysChem, 20(4), 618-626
Open this publication in new window or tab >>Excited-State Dynamics of [Ru(bpy)(3)](2+) Thin Films on Sensitized TiO2 and ZrO2
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2019 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 20, no 4, p. 618-626Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
Excited-state electron transfer, Ru(bpy)(3), DSSCs, Photochemistry, Solid state
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-245921 (URN)10.1002/cphc.201801010 (DOI)000458952600016 ()30623544 (PubMedID)2-s2.0-85061237720 (Scopus ID)
Note

QC 20190312

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-03-12Bibliographically approved
Wang, L., Sheibani, E., Guo, Y., Zhang, W., Li, Y., Liu, P., . . . Sun, L. (2019). Impact of Linking Topology on the Properties of Carbazole-Based Hole-Transport Materials and their Application in Solid-State Mesoscopic Solar Cells. SOLAR RRL, Article ID 1900196.
Open this publication in new window or tab >>Impact of Linking Topology on the Properties of Carbazole-Based Hole-Transport Materials and their Application in Solid-State Mesoscopic Solar Cells
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2019 (English)In: SOLAR RRL, ISSN 2367-198X, article id 1900196Article in journal (Refereed) Epub ahead of print
Abstract [en]

Carbazole is a promising core for the molecular design of hole-transport materials (HTMs) for solid-state mesoscopic solar cells (ssMSCs), such as solid-state dye-sensitized solar cells (ssDSSCs) and perovskite solar cells (PSCs) due to its low cost and excellent optoelectronic properties of its derivatives. Although carbazole-based HTMs are intensely investigated in ssMSCs and promising device performance is demonstrated, the fundamental understanding of the impact of linking topology on the properties of carbazole-based HTMs is lacking. Herein, the effect of the linking topology on the optical and electronic properties of a series of carbazole-based HTMs with 2,7-substitution and 3,6-substitution is systematically investigated. The results demonstrate that the 2,7-substituted carbazole-based HTMs display higher hole mobility and conductivity among this series of analogous molecules, thereby exhibiting better device performance. In addition, the conductivity of the HTMs is improved after light treatment, which explains the commonly observed light-soaking phenomenon of ssMSCs in general. All these carbazole-based HTMs are successfully applied in ssMSCs and one of the HTMs X50-based devices yield a promising efficiency of 6.8% and 19.2% in ssDSSCs and PSCs, respectively. This study provides guidance for the molecular design of effective carbazole-based HTMs for high-performance ssMSCs and related electronic devices.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
hole-transport materials, carbazole, linking topology, mesoscopic solar cells, perovskite solar cells
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-255742 (URN)10.1002/solr.201900196 (DOI)000477425300001 ()
Note

QC 20190813

Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13Bibliographically approved
Zhang, W., Sadollahkhani, A., Li, Y., Leandri, V., Gardner, J. M. & Kloo, L. (2019). Mechanistic Insights from Functional Group Exchange Surface Passivation: A Combined Theoretical and Experimental Study. ACS APPLIED ENERGY MATERIALS, 2(4), 2723-2733
Open this publication in new window or tab >>Mechanistic Insights from Functional Group Exchange Surface Passivation: A Combined Theoretical and Experimental Study
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2019 (English)In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 4, p. 2723-2733Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
Keywords
perovskite solar cells, polyhedral oligomeric silsesquioxane (POSS), passivation, DFT calculation, stability
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-251284 (URN)10.1021/acsaem.9b00050 (DOI)000465644600047 ()
Note

QC 20190517

Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-05-17Bibliographically approved
Starkholm, A., Kloo, L. & Svensson, P. H. (2019). Polyiodide Hybrid Perovskites: A Strategy To Convert Intrinsic 2D Systems into 3D Photovoltaic Materials. ACS Applied Energy Materials, 2(1), 477-485
Open this publication in new window or tab >>Polyiodide Hybrid Perovskites: A Strategy To Convert Intrinsic 2D Systems into 3D Photovoltaic Materials
2019 (English)In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 2, no 1, p. 477-485Article in journal (Refereed) Published
Abstract [en]

Two new organic inorganic hybrid perovskite compounds, (Me3S)(2)Pb5I14*2I(2) (1) and (C8H11S)(2)Pb2I6*I-2 (2), have been synthesized and subsequently characterized in this study. The materials were synthesized from facile one-pot, one-step reactions of lead iodide, corresponding sulfide, methanol, iodine, and hydroiodic acid in the case of 2. Structural analysis reveals the presence of polyiodide entities in both compounds. Compound 1 contains triiodide anions, I-3(-), that are uniquely shared between the 2D inorganic slabs, forming a 3D network. Both 1 and 2 have I-2 molecules that are bridging the inorganic slabs through a structural motif that can be regarded as a tetraiodide anion, I-4(2-). Optical spectroscopy shows band gaps of 1.86 eV for 1 and 1.89 eV for 2. The optoelectronic properties were further investigated with band structure calculations. Single-crystal IV-characteristics of 1 show that the compound is photoactive confirming it as a promising photovoltaic candidate. Compound 1 highlights a novel strategy of designing 3D semiconducting hybrid materials by incorporating polyiodides to provide direct geometric and electronic connections between the semiconducting inorganic perovskite sheets.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
organic inorganic hybrid materials, perovskites, polyiodide, solar cells, dimensionality, iodine
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-245958 (URN)10.1021/acsaem.8b01507 (DOI)000458706900060 ()
Note

QC 20190314

Available from: 2019-03-14 Created: 2019-03-14 Last updated: 2019-03-14Bibliographically approved
Trilaksana, H., Shearer, C., Kloo, L. & Andersson, G. G. (2019). Restructuring of Dye Layers in Dye Sensitized Solar Cells: Cooperative Adsorption of N719 and Chenodeoxycholic Acid on Titania. ACS Applied Energy Materials, 2(1), 124-130
Open this publication in new window or tab >>Restructuring of Dye Layers in Dye Sensitized Solar Cells: Cooperative Adsorption of N719 and Chenodeoxycholic Acid on Titania
2019 (English)In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 2, no 1, p. 124-130Article in journal (Refereed) Published
Abstract [en]

The effect of the co-adsorbent chenodeoxycholic acid (CDCA) up to a concentration of 20 mM on the adsorption of the dye N719 onto titania has been investigated using neutral impact collision ion scattering spectroscopy. It is shown that the co-adsorption of CDCA changes the adsorption mode of N719 from multilayer toward monolayer. FT-IR spectroscopy shows that the adsorption of CDCA increases with increasing CDCA concentration. In contrast, the amount of N719 adsorbed onto titania shows a minimum at 10 mM CDCA, and the relationship between the amount of CDCA and of N719 adsorbed onto titania depends nonmonotonically on the CDCA concentration. The co-adsorption of CDCA and N719 can be described as cooperative. The effect is observed for both low and high N719 concentrations.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
dye sensitized solar cells, co-adsorbent, monolayer, multilayer, concentration depth profiles, neutral impact collision ion scattering spectroscopy
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-245957 (URN)10.1021/acsaem.8b01864 (DOI)000458706900015 ()
Note

QC 20190314

Available from: 2019-03-14 Created: 2019-03-14 Last updated: 2019-03-14Bibliographically approved
Abdelhamid, H. N., El-Zohry, A. M., Cong, J., Thersleff, T., Karlsson, K. M., Kloo, L. & Zou, X. (2019). Towards implementing hierarchical porous zeolitic imidazolate frameworks in dye-sensitized solar cells. Royal Society Open Science, 6(7), Article ID 190723.
Open this publication in new window or tab >>Towards implementing hierarchical porous zeolitic imidazolate frameworks in dye-sensitized solar cells
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2019 (English)In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 6, no 7, article id 190723Article in journal (Refereed) Published
Abstract [en]

A one-pot method for encapsulation of dye, which can be applied for dye-sensitized solar cells (DSSCs), and synthesis of hierarchical porous zeolitic imidazolate frameworks (ZIF-8), is reported. The size of the encapsulated dye tunes the mesoporosity and surface area of ZIF-8. The mesopore size, Langmuir surface area and pore volume are 15 nm, 960-1500 m(2). g(-1) and 0.36-0.61 cm(3). g(-1), respectively. After encapsulation into ZIF-8, the dyes show longer emission lifetimes (greater than 4-8-fold) as compared to the corresponding non-encapsulated dyes, due to suppression of aggregation, and torsional motions.

Place, publisher, year, edition, pages
Royal Society Publishing, 2019
Keywords
zeolitic imidazolate frameworks, hierarchical Porous ZIF-8, dye encapsulation, dye-sensitized solar cells, photophysical properties, emission lifetime
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-257464 (URN)10.1098/rsos.190723 (DOI)000479146300079 ()31417762 (PubMedID)2-s2.0-85070743581 (Scopus ID)
Note

QC 20190830

Available from: 2019-08-30 Created: 2019-08-30 Last updated: 2019-08-30Bibliographically approved
Yang, W., Hao, Y., Kloo, L. & Boschloo, G. (2018). Carrier Dynamics of Dye Sensitized-TiO2 in Contact with Different Cobalt Complexes in the Presence of Tri(p-anisyl)amine Intermediates. The Journal of Physical Chemistry C, 122(26), 14345-14354
Open this publication in new window or tab >>Carrier Dynamics of Dye Sensitized-TiO2 in Contact with Different Cobalt Complexes in the Presence of Tri(p-anisyl)amine Intermediates
2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 26, p. 14345-14354Article in journal (Refereed) Published
Abstract [en]

Heterogeneous charge transfer processes at sensitized wide bandgap semiconductor surfaces are imperative for both fundamental knowledge and technical applications. Herein, we focus on the investigation of carrier dynamics of a triphenylamine-based dye, LEG4, sensitized TiO2 (LEG4/TiO2) in contact with two types of electrolyte systems: pure cobalt-based electrolytes and in combination with an organic donor, tri(p-anisyl)amine (TPAA). Four different cobalt redox systems with potentials spanning a 0.3 V range were studied, and the carrier recombination and regeneration kinetics were monitored both at low and at high TiO2 (e(-)) densities (1.3 X 10(18) and 1.3 X 10(19) cm(-3), respectively). The results reveal that the introduction of the TPAA intermediate more effectively suppress the recombination loss of TiO2 (e(-)) under high charge conditions, close to open-circuit, as compared to low charge conditions. As a result, the charge transfer from the cobalt complexes to the oxidized dyes is significantly improved by the addition of TPAA. Dye-sensitized solar cells fabricated with the TPAA-containing electrolytes demonstrate remarkable improvement in both V-OC and J(SC) and lead to more than 25% increase of the light-to-electricity conversion efficiency. Furthermore, an unprecedented detrimental impact of TPAA on the device performance was identified when the redox potential of the TPAA donor and the cobalt complexes are close. This is ascribed to the formation of TPAA(center dot+) which can act as an active recombination centers and thus lower the solar cell performance. These insights point at a strategy to enhance the lifetimes of electrons generated in sensitized semiconductor electrodes by overcoming the charge recombination between TiO2 and the oxidized dye under high carrier densities in the semiconductor substrate and offer practical guidance to the design of future efficient electrolyte systems for dye-sensitized solar cells.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-232616 (URN)10.1021/acs.jpcc.8b03395 (DOI)000438178900013 ()2-s2.0-85048726885 (Scopus ID)
Funder
Swedish Energy AgencySwedish Research CouncilStiftelsen Olle Engkvist Byggmästare
Note

QC 20180731

Available from: 2018-07-31 Created: 2018-07-31 Last updated: 2018-10-16Bibliographically approved
Hua, Y., Liu, P., Li, Y., Sun, L. & Kloo, L. (2018). Composite Hole-Transport Materials Based on a Metal-Organic Copper Complex and Spiro-OMeTAD for Efficient Perovskite Solar Cells. SOLAR RRL, 2(5), Article ID UNSP 1700073.
Open this publication in new window or tab >>Composite Hole-Transport Materials Based on a Metal-Organic Copper Complex and Spiro-OMeTAD for Efficient Perovskite Solar Cells
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2018 (English)In: SOLAR RRL, ISSN 2367-198X, Vol. 2, no 5, article id UNSP 1700073Article in journal (Refereed) Published
Abstract [en]

Spiro-OMeTAD has been the most commonly used hole-transport material in perovskite solar cells. However, this material shows intrinisic drawbacks, such as low hole mobility and conductivity in its pristine form, as well as self-aggregation when deposited as thin film. These are not beneficial properties for efficient hole transport and extraction. In order to address these issues, we have designed a new type of composite hole-transport materials based on a new metal-organic copper complex (CuH) and Spiro-OMeTAD. The incorporation of the molecularly bulky HTM CuH into the Spiro-OMeTAD material efficiently improves the hole mobility and suppresses the aggregation in the Spiro-OMeTAD film. As a result, the conversion efficiencies obtained for perovskite solar cells based on the composite HTM system reached as high as 18.83%, which is superior to solar cells based on the individual hole-transport materials CuH (15.75%) or Spiro-OMeTAD (14.47%) under the same working conditions. These results show that composite HTM systems may constitute an effective strategy to further improve the efficiency of perovskite solar cells.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
Hole transport materials, mobility, perovskite solar cells, small molecules
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-228439 (URN)10.1002/solr.201700073 (DOI)000432036200001 ()
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-05-29Bibliographically approved
Xu, P., Liu, P., Li, Y., Xu, B., Kloo, L., Sun, L. & Hua, Y. (2018). D-A-D-Typed Hole Transport Materials for Efficient Perovskite Solar Cells: Tuning Photovoltaic Properties via the Acceptor Group. ACS Applied Materials and Interfaces, 10(23), 19697-19703
Open this publication in new window or tab >>D-A-D-Typed Hole Transport Materials for Efficient Perovskite Solar Cells: Tuning Photovoltaic Properties via the Acceptor Group
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 23, p. 19697-19703Article in journal (Refereed) Published
Abstract [en]

Two D-A-D-structured hole-transport materials (YN1 and YN2) have been synthesized and used in perovskite solar cells. The two HTMs have low-lying HOMO levels and impressive mobility. Perovskite-based solar cells (PSCs) fabricated with YN2 showed a power conversion efficiency (PCE) value of 19.27% in ambient air, which is significantly higher than that of Spiro-OMeTAD (17.80%). PSCs based on YN1 showed an inferior PCE of 16.03%. We found that the incorporation of the stronger electron-withdrawing group in the HTM YN2 improves the PCE of PSCs. Furthermore, the YN2-based PSCs exhibit good long-term stability retaining 91.3% of its initial efficiency, whereas PSCs based on Spiro-OMeTAD retained only 42.2% after 1000 h lifetime (dark conditions). These promising results can provide a new strategy for the design of D-A-D HTMs for PSC applications in future.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
acceptor, hole-transport material, mobility, perovskite solar cells, spiro-OMeTAD
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-238197 (URN)10.1021/acsami.8b04003 (DOI)000435525100045 ()29785846 (PubMedID)2-s2.0-85047487298 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Energy Agency
Note

QC 20181119

Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-11-19Bibliographically approved
Wang, L., Zhang, J., Liu, P., Xu, B., Zhang, B., Chen, H., . . . Sun, L. (2018). Design and synthesis of dopant-free organic hole-transport materials for perovskite solar cells. Chemical Communications, 54(69)
Open this publication in new window or tab >>Design and synthesis of dopant-free organic hole-transport materials for perovskite solar cells
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2018 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, no 69Article in journal (Refereed) Published
Abstract [en]

Two novel dopant-free hole-transport materials (HTMs) with spiro[dibenzo[c,h]xanthene-7,9-fluorene] (SDBXF) skeletons were prepared via facile synthesis routes. A power conversion efficiency of 15.9% in perovskite solar cells is attained by using one HTM without dopants, which is much higher than undoped Spiro-OMeTAD-based devices (10.8%). The crystal structures of both new HTMs were systematically investigated to reveal the reasons behind such differences in performance and to indicate the design principles of more advanced HTMs.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:kth:diva-234569 (URN)10.1039/c8cc04026e (DOI)000442605100002 ()30043013 (PubMedID)2-s2.0-85052539543 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2019-08-20Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0168-2942

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