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Publications (10 of 212) Show all publications
Svanström, S., Jacobsson, J., Boschloo, G., Johansson, E., Rensmo, H. & Cappel, U. B. (2020). Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites. ACS Applied Materials and Interfaces, 12(6), 7212-7221
Open this publication in new window or tab >>Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites
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2020 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 6, p. 7212-7221Article in journal (Refereed) Published
Abstract [en]

Lead halide perovskite solar cells have significantly increased in both efficiency and stability over the last decade. An important aspect of their longterm stability is the reaction between the perovskite and other materials in the solar cell. This includes the contact materials and their degradation if they can potentially come into contact through, e.g., pinholes or material diffusion and migration. Here, we explore the interactions of silver contacts with lead halide perovskites of different compositions by using a model system where thermally evaporated silver was deposited directly on the surface of the perovskites. Using X-ray photoelectron spectroscopy with support from scanning electron microscopy, X-ray diffraction, and UV-visible absorption spectroscopy, we studied the film formation and degradation of silver on perovskites with different compositions. The deposited silver does not form a continuous silver film but instead tends to form particles on a bare perovskite surface. These particles are initially metallic in character but degrade into AgI and AgBr over time. The degradation and migration appear unaffected by the replacement of methylammonium with cesium but are significantly slowed down by the complete replacement of iodide with bromide. The direct contact between silver and the perovskite also significantly accelerates the degradation of the perovskite, with a significant loss of organic cations and the possible formation of PbO, and, at the same time, changed the surface morphology of the iodide-rich perovskite interface. Our results further indicate that an important degradation pathway occurred through gas-phase perovskite degradation products. This highlights the importance of control over the interface materials and the use of completely hermetical barrier layers for the long-term stability and therefore the commercial viability of silver electrodes.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
perovskite solar cells, electrode stability, X-ray photoelectron spectroscopy, interface chemistry, noble metal electrodes
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407282 (URN)10.1021/acsami.9b20315 (DOI)000514256400040 ()31958007 (PubMedID)
Funder
Swedish Research Council, VR 2018-04125Swedish Research Council, 2018-06465Swedish Research Council, 2018-04330Swedish Foundation for Strategic Research , RMA15-0130Swedish Energy Agency, P43549-1StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2020-03-23 Created: 2020-03-23 Last updated: 2020-03-23Bibliographically approved
Kim, B. J., Kwon, S. L., Kim, M.-c., Jin, Y. U., Lee, D. G., Jeon, J. B., . . . Jung, H. S. (2020). High-Efficiency Flexible Perovskite Solar Cells Enabled by an Ultrafast Room-Temperature Reactive Ion Etching Process. ACS Applied Materials and Interfaces, 12(6), 7125-7134
Open this publication in new window or tab >>High-Efficiency Flexible Perovskite Solar Cells Enabled by an Ultrafast Room-Temperature Reactive Ion Etching Process
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2020 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 6, p. 7125-7134Article in journal (Refereed) Published
Abstract [en]

Perovskite solar cells (PSCs), which have surprisingly emerged in recent years, are now aiming at commercialization. Rapid, low-temperature, and continuous fabrication processes that can produce high-efficiency PSCs with a reduced fabrication cost and shortened energy payback time are important challenges on the way to commercialization. Herein, we report a reactive ion etching (RIE) method, which is an ultrafast room-temperature technique, to fabricate mesoporous TiO2 (mp-TiO2) as an electron transport layer for high-efficiency PSCs. Replacing the conventional high-temperature annealing process by RIE reduces the total processing time for fabricating 20 PSCs by 40%. Additionally, the RIE-processed mp-TiO2 exhibits enhanced electron extraction, whereupon the optimized RIE-mp-TiO2-based PSC exhibits a power conversion efficiency (PCE) of 19.60% without JV hysteresis, when the devices were optimized with a TiCl4 surface treatment process. Finally, a flexible PSC employing RIE-mp-TiO2 is demonstrated with 17.29% PCE. Considering that the RIE process has been actively used in the semiconductor industry, including for the fabrication of silicon photovoltaic modules, the process developed in this work could be easily applied toward faster, simpler, and cheaper manufacturing of PSC modules.

Keywords
perovskite, solar cells, reactive ion etching, flexible device, low-temperature process
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407443 (URN)10.1021/acsami.9b19030 (DOI)000514256400031 ()31958005 (PubMedID)
Funder
Swedish Energy Agency, 43294-1
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-03-25Bibliographically approved
Nonomura, K., Vlachopoulos, N., Unger, E., Häggman, L., Hagfeldt, A. & Boschloo, G. (2019). Blocking the Charge Recombination with Diiodide Radicals by TiO2 Compact Layer in Dye-Sensitized Solar Cells. Journal of the Electrochemical Society, 166(9), B3203-B3208
Open this publication in new window or tab >>Blocking the Charge Recombination with Diiodide Radicals by TiO2 Compact Layer in Dye-Sensitized Solar Cells
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2019 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 9, p. B3203-B3208Article in journal (Refereed) Published
Abstract [en]

The addition of a compact titanium dioxide (TiO2) layer between the fluorine-doped tin oxide (FTO) coated glass substrate and the mesoporous TiO2 layer in the dye-sensitized solar cell (DSC) based on the iodide/triiodide redox couple (I-/I-3(-)) is known to improve its current-voltage characteristics. The compact layer decreases the recombination of electrons extracted through the FTO layer with I-3(-) around the maximum power point. Furthermore, the short-circuit photocurrent was improved, which previously has been attributed to the improved light transmittance and/or better contact between TiO2 and FTO. Here, we demonstrate that the compact TiO2 layer has another beneficial effect: it blocks the reaction between charge carriers in the FTO and photogenerated diiodide radical species (I-2(-center dot)). Using photomodulated voltammetry, it is demonstrated that the cathodic photocurrent found at bare FTO electrodes is blocked by the addition of a compact TiO2 layer, while the anodic photocurrent due to reaction with I-2(-center dot) is maintained.

Place, publisher, year, edition, pages
ELECTROCHEMICAL SOC INC, 2019
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-383838 (URN)10.1149/2.0281909jes (DOI)000466839800002 ()
Funder
Swedish Energy AgencySwedish Research Council, 2015-00163Knut and Alice Wallenberg Foundation
Available from: 2019-05-27 Created: 2019-05-27 Last updated: 2019-05-27Bibliographically approved
Johansson, M. B., Philippe, B., Banerjee, A., Phuyal, D., Mukherjee, S., Chakraborty, S., . . . Johansson, E. (2019). Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3. Inorganic Chemistry, 58(18), 12040-12052
Open this publication in new window or tab >>Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3
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2019 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 18, p. 12040-12052Article in journal (Refereed) Published
Abstract [en]

Metal halide compounds with photovoltaic properties prepared from solution have received increased attention for utilization in solar cells. In this work, low-toxicity cesium bismuth iodides are synthesized from solution, and their photovoltaic and, optical properties as well as electronic and crystal structures are investigated. The X-ray diffraction patterns reveal that a CsI/BiI3 precursor ratio of 1.5:1 can convert pure rhombohedral BiI3 to pure hexagonal Cs3Bi2I9, but any ratio intermediate of this stoichiometry and pure BiI3 yields a mixture containing the two crystalline phases Cs3Bi2I9 and BiI3, with their relative fraction depending on the CsI/BiI3 ratio. Solar cells from the series of compounds are characterized, showing the highest efficiency for the compounds with a mixture of the two structures. The energies of the valence band edge were estimated using hard and soft X-ray photoelectron spectroscopy for more bulk and surface electronic properties, respectively. On the basis of these measurements, together with UV-vis-near-IR spectrophotometry, measuring the band gap, and Kelvin probe measurements for estimating the work function, an approximate energy diagram has been compiled clarifying the relationship between the positions of the valence and conduction band edges and the Fermi level.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-395308 (URN)10.1021/acs.inorgchem.9b01233 (DOI)000486565600024 ()31483638 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasSwedish Foundation for Strategic Research
Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-10-18Bibliographically approved
Michaels, H., Benesperi, I., Edvinsson, T., Munoz-Garcia, A. B., Pavone, M., Boschloo, G. & Freitag, M. (2019). Correction: Michaels, H.; et al. Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells. Inorganics 2018, 6, 53. Inorganics, 7(11), Article ID 130.
Open this publication in new window or tab >>Correction: Michaels, H.; et al. Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells. Inorganics 2018, 6, 53
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2019 (English)In: Inorganics, ISSN 2304-6740, Vol. 7, no 11, article id 130Article in journal (Refereed) Published
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-400431 (URN)10.3390/inorganics7110130 (DOI)000500003800001 ()
Note

Correction for: Inorganics, vol. 6, issue 2, article number: 53.

Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2019-12-20Bibliographically approved
Boschloo, G. (2019). Improving the Performance of Dye-Sensitized Solar Cells. Frontiers in Chemistry, 7, Article ID 77.
Open this publication in new window or tab >>Improving the Performance of Dye-Sensitized Solar Cells
2019 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 7, article id 77Article in journal (Refereed) Published
Abstract [en]

Dye-sensitized solar cells have been investigated intensively during the last three decades. Nevertheless, there are still many aspects to be explored to further improve their performance. Dye molecules can be modified endlessly for better performance. For instance, steric groups can be introduced to slow down recombination reactions and avoid unfavorable aggregation. There is a need for more optimal dye packing on the mesoporous TiO2 surface to increase light absorption and promote a better blocking effect. Novel redox mediators and HTMs are key elements to reach higher performing DSC as they can offer much higher output voltage than the traditional triiodide/iodide redox couple.

Place, publisher, year, edition, pages
FRONTIERS MEDIA SA, 2019
Keywords
mesoporous TiO2, recombination, electron lifetime, cobalt-complex, maximum power point, organic dyes
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-378375 (URN)10.3389/fchem.2019.00077 (DOI)000458674700001 ()
Funder
StandUp
Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-03-07Bibliographically approved
Gao, J., Yang, W., El-Zohry, A. M., Prajapati, G. K., Fang, Y., Dai, J., . . . Kloo, L. (2019). Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells. Journal of Materials Chemistry A, 7(33), 19495-19505
Open this publication in new window or tab >>Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 33, p. 19495-19505Article in journal (Refereed) Published
Abstract [en]

Lithium-ion-free tris(2,2 '-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)(3)](3+) and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)(3)](3+)/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)(3)](3+) upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical J(sc)-V-oc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Physical Chemistry Materials Chemistry Other Chemistry Topics
Identifiers
urn:nbn:se:uu:diva-394051 (URN)10.1039/c9ta07198a (DOI)000482139000027 ()
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2019-10-04 Created: 2019-10-04 Last updated: 2019-10-04Bibliographically approved
Tian, L., Törndahl, T., Ling, J., Pati, P. B., Zhang, Z.-B., Kubart, T., . . . Tian, H. (2019). Mechanistic Insights into Solid-State p-Type Dye-Sensitized Solar Cells. The Journal of Physical Chemistry C, 123(43), 26151-26160
Open this publication in new window or tab >>Mechanistic Insights into Solid-State p-Type Dye-Sensitized Solar Cells
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 43, p. 26151-26160Article in journal (Refereed) Published
Abstract [en]

The study of p-type dye sensitized solar cells (p-DSCs) is appealing but challenging. Although the devices have been studied for 20 years, the light conversion efficiency lags far behind those of n-DSCs. Very recently, on the basis of a core-shell structure, a novel solid-state p-DSC (p-ssDSCs) has been fabricated, which showed great enhancement in open-circuit voltage and dye regeneration rate. To further improve the performance of such devices, charge diffusion, recombination process, and the main limiting factors have to be understood. In the present paper, core-shell p-ssDSCs with ZnO as an electron conductor were fabricated by atomic layer deposition. The charge transport time was determined to be ca. 0.1 ms, which is about 2 orders of magnitude faster than those of typical liquid devices with I-/I-3(-) as a redox mediator. As a consequence, the devices exhibit the highest reported charge diffusion coefficient (D-d)' among p-DSCs. It is ascribed to an electron-limiting diffusion process by the ambipolar diffusion model, suggesting a different charge-transport-determining mechanism in contrast to liquid p-DSCs. The charge recombination rate is 1-2 orders of magnitude slower than its charge transport time, mandating that the estimated charge collection efficiency is near unity. Detailed analysis of the incident photon-to-electron conversion efficiency suggests that the energy conversion efficiency in these p-ssDSCs is currently limited by a large fraction of dyes that is not fully electrically connected in the device.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Physical Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-397591 (URN)10.1021/acs.jpcc.9b08251 (DOI)000493865700013 ()
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2020-01-15Bibliographically approved
Jeon, J. B., Kim, B. J., Bang, G. J., Kim, M.-C., Lee, D. G., Lee, J. M., . . . Jung, H. S. (2019). Photo-annealed amorphous titanium oxide for perovskite solar cells. Nanoscale, 11(41), 19488-19496
Open this publication in new window or tab >>Photo-annealed amorphous titanium oxide for perovskite solar cells
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 41, p. 19488-19496Article in journal (Refereed) Published
Abstract [en]

Electron selective layers are important to the efficiency, stability and hysteresis of perovskite solar cells. Photo-annealing is a low-cost, roll-to-roll-compatible process that can be applied to the post-treatment fabrication of sol-gel based metal oxide layers. Here, we fabricate an amorphous titanium oxide electron selective layer at a low temperature in a dry atmosphere using a UV light annealing system and compare it with a thermal annealing process. Active oxygen species are created by using UV light to promote hydrolysis and condense the TiO2 precursor, which removes organic ligands effectively. The photo-annealed TiO2-based perovskite solar cell has a power conversion efficiency of 19.37% without hysteresis.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-400105 (URN)10.1039/c9nr05776e (DOI)000498821300046 ()31552996 (PubMedID)
Funder
Swedish Energy Agency, 43294-1
Available from: 2019-12-19 Created: 2019-12-19 Last updated: 2019-12-19Bibliographically approved
Jain, S. M., Phuyal, D., Davies, M. L., Li, M., Philippe, B., De Castro, C., . . . Durrant, J. R. (2018). An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)(3)Bi2I9 bismuth-based perovskite solar cells for improved performance and long-term stability. Nano Energy, 49, 614-624
Open this publication in new window or tab >>An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)(3)Bi2I9 bismuth-based perovskite solar cells for improved performance and long-term stability
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 49, p. 614-624Article in journal (Refereed) Published
Abstract [en]

We present a controlled, stepwise formation of methylammonium bismuth iodide (CH3NH3)(3)Bi2I9 perovskite films prepared via the vapour assisted solution process (VASP) by exposing BiI3 films to CH3NH3I (MAI) vapours for different reaction times, (CH3NH3)(3)Bi2I9 semiconductor films with tunable optoelectronic properties are obtained. Solar cells prepared on mesoporous TiO2 substrates yielded hysteresis-free efficiencies upto 3.17% with good reproducibility. The good performance is attributed mainly to the homogeneous surface coverage, improved stoichiometry, reduced metallic content in the bulk, and desired optoelectronic properties of the absorbing material. In addition, solar cells prepared using pure BiI3 films without MAI exposure achieved a power conversion efficiency of 0.34%. The non-encapsulated (CH3NH3)(3)Bi2I9 devices were found to be stable for as long as 60 days with only 0.1% drop in efficiency. This controlled formation of (CH3NH3)(3)Bi2I9 perovskite films highlights the benefit of the VASP technique to optimize material stoichiometry, morphology, solar cell performance, and long-term durability.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Vapour assisted solution process (VASP), Lead free perovskite, (CH3NH3)(3)Bi2I9, Morphological tailoring, High resolution X-ray photoelectron (HAXPES) spectroscopy
National Category
Materials Chemistry Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-358277 (URN)10.1016/j.nanoen.2018.05.003 (DOI)000434829500071 ()
Funder
Swedish Research CouncilEU, Horizon 2020, 663830
Available from: 2018-08-27 Created: 2018-08-27 Last updated: 2018-10-26Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8249-1469

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