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Publications (8 of 8) Show all publications
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: 2019-12-09Bibliographically approved
Phuyal, D., Safdari, M., Pazoki, M., Liu, P., Philippe, B., Kyashnina, K. O., . . . Gardner, J. M. (2018). Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study. Chemistry of Materials, 30(15), 4959-4967
Open this publication in new window or tab >>Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study
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2018 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 15, p. 4959-4967Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-234611 (URN)10.1021/acs.chemmater.8b00909 (DOI)000442186500014 ()2-s2.0-85050821628 (Scopus ID)
Note

QC 20180914

Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2019-12-09Bibliographically approved
Gao, J., El-Zohry, A. M., Trilaksana, H., Gabrielsson, E., Leandri, V., Ellis, H., . . . Kloo, L. (2018). Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect. ACS Applied Materials and Interfaces, 10(31), 26241-26247
Open this publication in new window or tab >>Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 31, p. 26241-26247Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
dye-sensitized solar cells, electrolyte, interface, dynamics, light soaking
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-234184 (URN)10.1021/acsami.8b06897 (DOI)000441477800045 ()29996051 (PubMedID)2-s2.0-85049917640 (Scopus ID)
Note

QC 20181003

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2019-12-09Bibliographically approved
Sadollahkhani, A., Liu, P., Leandri, V., Safdari, M., Zhang, W. & Gardner, J. M. (2017). Energetic Barriers to Interfacial Charge Transfer and Ion Movement in Perovskite Solar Cells. ChemPhysChem, 18(21), 3047-3055
Open this publication in new window or tab >>Energetic Barriers to Interfacial Charge Transfer and Ion Movement in Perovskite Solar Cells
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2017 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 18, no 21, p. 3047-3055Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keywords
capacitance, diode ideality, interfacial charge transfer, ion movement, perovskite solar cells
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-217936 (URN)10.1002/cphc.201700740 (DOI)000414406400013 ()28840632 (PubMedID)2-s2.0-85030154725 (Scopus ID)
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2019-12-09Bibliographically approved
Safdari, M., Phuyal, D., Philippe, B., Svensson, P. H., Butorin, S. M., Kvashnina, K. O., . . . Gardner, J. M. (2017). Impact of Synthetic Route on Structural and Physical Properties of Butyl-1,4-Diammonium Lead Iodide Semiconductors. Journal of Materials Chemistry A
Open this publication in new window or tab >>Impact of Synthetic Route on Structural and Physical Properties of Butyl-1,4-Diammonium Lead Iodide Semiconductors
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2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488Article in journal (Refereed) Accepted
Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-200279 (URN)
Note

QC 20170123

Available from: 2017-01-23 Created: 2017-01-23 Last updated: 2019-12-09Bibliographically approved
Zhang, W., Liu, P., Sadollahkhani, A., Li, Y., Zhang, B., Zhang, F., . . . Kloo, L. (2017). Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells. ACS OMEGA, 2(12), 9231-9240
Open this publication in new window or tab >>Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells
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2017 (English)In: ACS OMEGA, ISSN 2470-1343, Vol. 2, no 12, p. 9231-9240Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-221019 (URN)10.1021/acsomega.7b01434 (DOI)000418744400078 ()2-s2.0-85040066582 (Scopus ID)
Funder
Swedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20180112

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2020-02-04Bibliographically approved
Safdari, M., Fischer, A. C., Xu, B., Kloo, L. & Gardner, J. M. (2015). Erratum to: Structure and function relationships in alkylammonium lead(II) iodide solar cells. Journal of Materials Chemistry A, 3(17), 9317-9317
Open this publication in new window or tab >>Erratum to: Structure and function relationships in alkylammonium lead(II) iodide solar cells
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2015 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 17, p. 9317-9317Article in journal (Refereed) Published
Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2015
National Category
Biomaterials Science
Identifiers
urn:nbn:se:kth:diva-242771 (URN)10.1039/c5ta90073e (DOI)000353420800051 ()2-s2.0-84928485590 (Scopus ID)
Note

QC 20190211

Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-12-09Bibliographically approved
Safdari, M., Phuyal, D., Liu, P., Philippe, B., Kvashnina, K. O., Butorin, S. M., . . . Gardner, J. M.Electronic structure of 2D Lead (II) Iodide Perovskites: An Experimental and Theoretical Study.
Open this publication in new window or tab >>Electronic structure of 2D Lead (II) Iodide Perovskites: An Experimental and Theoretical Study
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(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-200290 (URN)
Note

QC 20170123

Available from: 2017-01-23 Created: 2017-01-23 Last updated: 2019-12-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0387-2993

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