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Publications (10 of 25) Show all publications
Zhang, X., Qiu, W., Song, W., Hawash, Z., Wang, Y., Pradhan, B., . . . Poortmans, J. (2022). An Integrated Bulk and Surface Modification Strategy for Gas-Quenched Inverted Perovskite Solar Cells with Efficiencies Exceeding 22%. Solar RRL, 6(6), Article ID 2200053.
Open this publication in new window or tab >>An Integrated Bulk and Surface Modification Strategy for Gas-Quenched Inverted Perovskite Solar Cells with Efficiencies Exceeding 22%
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2022 (English)In: Solar RRL, E-ISSN 2367-198X, Vol. 6, no 6, article id 2200053Article in journal (Refereed) Published
Abstract [en]

Inverted perovskite solar cells (PSCs) prepared by the antisolvent method have achieved power conversion efficiencies (PCEs) of over 23%, but they are not ideal for device upscaling. In contrast, gas-quenched PSCs offer great potential for upscaling, but their performance still lags behind. Herein, the gas-quenched films through both surface and bulk modifications are upgraded. First, a novel surface modifier, benzylammonium thiocyanate, is found to allow remarkably improved surface properties, but the PCE gain is limited by the existence of longitudinally multiple grains. Thus, methylammonium chloride additive as a second modifier to realize monolithic grains is further utilized. Such an integrated strategy enables the average open-circuit voltage of the gas-quenched PSCs to increase from 1.08 to 1.15 V, leading to a champion PCE of 22.3%. Moreover, the unencapsulated device shows negligible degradation after 150 h of maximum power point operation under simulated 1 sun illumination in N2.

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
Additive engineering, benzylammonium thiocyanate, gas quenching, inverted p-i-n perovskite solar cells, stabilities, surface treatments
National Category
Physical Sciences Chemical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-89421 (URN)10.1002/solr.202200053 (DOI)000770000400001 ()2-s2.0-85126381426 (Scopus ID)
Available from: 2022-04-08 Created: 2022-04-08 Last updated: 2022-09-15Bibliographically approved
Susic, I., Zanoni, K. P. S., Paliwal, A., Kaya, I. C., Hawash, Z., Sessolo, M., . . . Bolink, H. J. (2022). Intrinsic Organic Semiconductors as Hole Transport Layers in p–i–n Perovskite Solar Cells. Solar RRL, 6(4), Article ID 2100882.
Open this publication in new window or tab >>Intrinsic Organic Semiconductors as Hole Transport Layers in p–i–n Perovskite Solar Cells
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2022 (English)In: Solar RRL, E-ISSN 2367-198X, Vol. 6, no 4, article id 2100882Article in journal (Refereed) Published
Abstract [en]

Thin polymeric and small-molecular-weight organic semiconductors are widely employed as hole transport layers (HTLs) in perovskite solar cells. To ensure ohmic contact with the electrodes, the use of doping or additional high work function (WF) interlayer is common. In some cases, however, intrinsic organic semiconductors can be used without any additive or buffer layers, although their thickness must be tuned to ensure selective and ohmic hole transport. Herein, the characteristics of thin HTLs in vacuum-deposited perovskite solar cells are studied, and it is found that only very thin (<5 nm) HTLs readily result inhigh-performing devices, as the HTL acts as a WF enhancer while still ensuring selective hole transfer, as suggested by ultraviolet photoemission spectroscopy and Kelvin probe measurements. For thicker films (>= 5 nm), a dynamic behavior for consecutive electrical measurements is observed, a phenomenon which is also common to other widely used HTLs. Finally, it is found that despite their glass transition temperature, small-molecule HTLs lead to thermally unstable solar cells, asopposed to polymeric materials. The origin of the degradation is still not clear, but might be related to chemical reactions/diffusion at the HTL/perovskite interface, in detriment of the device stability

Place, publisher, year, edition, pages
John Wiley & Sons, 2022
Keywords
doping, hole transport layers, organic semiconductors, perovskite solar cells, small molecules
National Category
Chemical Sciences Physical Sciences Condensed Matter Physics
Research subject
Chemistry; Physics
Identifiers
urn:nbn:se:kau:diva-88066 (URN)10.1002/solr.202100882 (DOI)000736091600001 ()2-s2.0-85122056151 (Scopus ID)
Available from: 2022-01-13 Created: 2022-01-13 Last updated: 2022-04-21Bibliographically approved
Gil-Escrig, L., Dreessen, C., Palazon, F., Hawash, Z., Moons, E., Albrecht, S., . . . Bolink, H. J. (2021). Efficient Wide-Bandgap Mixed-Cation and Mixed-Halide Perovskite Solar Cells by Vacuum Deposition. ACS Energy Letters, 6(2), 827-836
Open this publication in new window or tab >>Efficient Wide-Bandgap Mixed-Cation and Mixed-Halide Perovskite Solar Cells by Vacuum Deposition
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2021 (English)In: ACS Energy Letters, E-ISSN 2380-8195, Vol. 6, no 2, p. 827-836Article in journal (Refereed) Published
Abstract [en]

Vacuum deposition methods are increasingly applied to the preparation of perovskite films and devices, in view of the possibility to prepare multilayer structures at low temperature. Vacuum-deposited, wide-bandgap solar cells based on mixed-cation and mixed-anion perovskites have been scarcely reported, due to the challenges associated with the multiple-source processing of perovskite thin films. In this work, we describe a four-source vacuum deposition process to prepare wide-bandgap perovskites of the type FA(1-n)Cs(n)Pb-(I1-xBrx)(3) with a tunable bandgap and controlled morphology, using FAI, CsI, PbI2, and PbBr2 as the precursors. The simultaneous sublimation of PbI2 and PbBr2 allows the relative Br/Cs content to be decoupled and controlled, resulting in homogeneous perovskite films with a bandgap in the 1.7-1.8 eV range and no detectable halide segregation. Solar cells based on 1.75 eV bandgap perovskites show efficiency up to 16.8% and promising stability, maintaining 90% of the initial efficiency after 2 weeks of operation.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2021
National Category
Materials Chemistry Physical Sciences Condensed Matter Physics
Research subject
Physics; Chemistry - Materials Science
Identifiers
urn:nbn:se:kau:diva-83542 (URN)10.1021/acsenergylett.0c02445 (DOI)000619803400063 ()2-s2.0-85101039246 (Scopus ID)
Available from: 2021-03-26 Created: 2021-03-26 Last updated: 2022-05-25Bibliographically approved
Choi, J. I., Khan, M. E., Hawash, Z., Lee, H., Ono, L. K., Qi, Y., . . . Park, J. Y. (2020). Surface Termination-Dependent Nanotribological Properties of Single-Crystal MAPbBr(3) Surfaces. The Journal of Physical Chemistry C, 124(2), 1484-1491
Open this publication in new window or tab >>Surface Termination-Dependent Nanotribological Properties of Single-Crystal MAPbBr(3) Surfaces
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2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 2, p. 1484-1491Article in journal (Refereed) Published
Abstract [en]

Atomistic characterization of surface termination and the corresponding mechanical properties of single-crystal methylammonium lead tribromide (MAPbBr(3)) are performed using combined atomic force microscopy (AFM) measurements and density functional theory (DFT) calculations. A clean MAPbBr(3) surface is obtained by in situ cleavage in ultrahigh vacuum at room temperature, and the subsequent AFM measurements of the as-cleaved MAPbBr(3) exhibit the coexistence of two different surface terrace types with step height differences corresponding to about half the thickness of a PbI6 octahedron layer. Concurrent friction force microscopy measurements show that the two surfaces result in two distinct friction values. Based on DFT calculations, we attribute the higher-friction and lower-friction surfaces to MABr-terminated flat and PbBr2-terminated vacant surface terminations, respectively. The calculated electronic band structures of the various MABr- and PbBr2-terminated surfaces show that the midgap states are absent, revealing the defect-tolerant nature of the ideal single-crystal MAPbBr(3) surfaces.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-83174 (URN)10.1021/acs.jpcc.9b10191 (DOI)000508467700028 ()
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2022-05-25Bibliographically approved
Choi, J. I., Khan, M. E., Hawash, Z., Kim, K. J., Lee, H., Ono, L. K., . . . Park, J. Y. (2019). Atomic-scale view of stability and degradation of single-crystal MAPbBr(3) surfaces. Journal of Materials Chemistry A, 7(36), 20760-20766
Open this publication in new window or tab >>Atomic-scale view of stability and degradation of single-crystal MAPbBr(3) surfaces
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 7, no 36, p. 20760-20766Article in journal (Refereed) Published
Abstract [en]

While organic-inorganic hybrid perovskite solar cells are emerging as promising candidates for next-generation solar cells with fascinating power conversion efficiency, the instability of perovskites remains a significant bottleneck for their commercialization. An atomic scale understanding of the degradation of hybrid perovskites, however, is only in its beginning stages because of the difficulty in preparing well-defined surface conditions for characterization. Using atomic force microscopy at ultra-high vacuum and room temperature, we report the first direct observation of the degradation process of a cleaved methylammonium lead bromide, MAPbBr(3) (MA: CH3NH3+), single crystal. Upon in situ cleavage, atomic force microscopy images show large flat terraces with monolayer height steps, which correspond to the surface of cubic MAPbBr(3) with methylammonium ligand termination. While this surface can be prepared via the cleavage process and is energetically stable, we observe that after several weeks under dark and vacuum conditions it degrades and produces clusters surrounded by pits. Guided by density functional theory calculations, we propose a degradation pathway that initiates even at low humidity levels and leads to the formation of surface PbBr2 species. We finally identify the electronic structure of the MA-bromine-terminated flat surface and find that it is correlated with a strong field-induced degradation of the MAPbBr(3) only at positive sample bias voltages.

National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-83177 (URN)10.1039/c9ta05883d (DOI)000488618600030 ()
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2022-05-05Bibliographically approved
Wu, Z., Liu, Z., Hu, Z., Hawash, Z., Qiu, L., Jiang, Y., . . . Qi, Y. (2019). Highly Efficient and Stable Perovskite Solar Cells via Modification of Energy Levels at the Perovskite/Carbon Electrode Interface. Advanced Materials, 31(11), Article ID 1804284.
Open this publication in new window or tab >>Highly Efficient and Stable Perovskite Solar Cells via Modification of Energy Levels at the Perovskite/Carbon Electrode Interface
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2019 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 31, no 11, article id 1804284Article in journal (Refereed) Published
Abstract [en]

Perovskite solar cells (PSCs) have attracted great attention in the past few years due to their rapid increase in efficiency and low-cost fabrication. How-ever, instability against thermal stress and humidity is a big issue hindering their commercialization and practical applications. Here, by combining thermally stable formamidinium-cesium-based perovskite and a moisture-resistant carbon electrode, successful fabrication of stable PSCs is reported, which maintain on average 77% of the initial value after being aged for 192 h under conditions of 85 degrees C and 85% relative humidity (the "double 85" aging condition) without encapsulation. However, the mismatch of energy levels at the interface between the perovskite and the carbon electrode limits charge collection and leads to poor device performance. To address this issue, a thin-layer of poly(ethylene oxide) (PEO) is introduced to achieve improved interfacial energy level alignment, which is verified by ultraviolet photoemission spectroscopy measurements. Indeed as a result, power conversion efficiency increases from 12.2% to 14.9% after suitable energy level modification by intentionally introducing a thin layer of PEO at the perovskite/carbon interface.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
carbon electrode, energy level alignment, perovskite solar cells, poly(ethylene oxide), stability
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-83179 (URN)10.1002/adma.201804284 (DOI)000461575300001 ()30680833 (PubMedID)
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2022-05-25Bibliographically approved
Chen, M., Ju, M.-G., Garces, H. F., Carl, A. D., Ono, L. K., Hawash, Z., . . . Padture, N. P. (2019). Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation. Nature Communications, 10, Article ID 16.
Open this publication in new window or tab >>Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation
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2019 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 10, article id 16Article in journal (Refereed) Published
Abstract [en]

There has been an urgent need to eliminate toxic lead from the prevailing halide perovskite solar cells (PSCs), but the current lead-free PSCs are still plagued with the critical issues of low efficiency and poor stability. This is primarily due to their inadequate photovoltaic properties and chemical stability. Herein we demonstrate the use of the lead-free, all-inorganic cesium tin-germanium triiodide (CsSn(0.5)Ge(0.5)l(3)) solid-solution perovskite as the light absorber in PSCs, delivering promising efficiency of up to 7.11%. More importantly, these PSCs show very high stability, with less than 10% decay in efficiency after 500 h of continuous operation in N-2 atmosphere under one-sun illumination. The key to this striking performance of these PSCs is the formation of a full-coverage, stable native-oxide layer, which fully encapsulates and passivates the perovskite surfaces. The native-oxide passivation approach reported here represents an alternate avenue for boosting the efficiency and stability of lead-free PSCs.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-83180 (URN)10.1038/s41467-018-07951-y (DOI)000454756600002 ()30604757 (PubMedID)
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2023-03-28Bibliographically approved
Jiang, Y., Remeika, M., Hu, Z., Juarez-Perez, E. J., Qiu, L., Liu, Z., . . . Qi, Y. (2019). Negligible-Pb-Waste and Upscalable Perovskite Deposition Technology for High-Operational-Stability Perovskite Solar Modules. Advanced Energy Materials, 9(13), Article ID 1803047.
Open this publication in new window or tab >>Negligible-Pb-Waste and Upscalable Perovskite Deposition Technology for High-Operational-Stability Perovskite Solar Modules
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2019 (English)In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 9, no 13, article id 1803047Article in journal (Refereed) Published
Abstract [en]

An upscalable perovskite film deposition method combining raster ultrasonic spray coating and chemical vapor deposition is reported. This method overcomes the coating size limitation of the existing stationary spray, single-pass spray, and spin-coating methods. In contrast with the spin-coating method (>90% Pb waste), negligible Pb waste during PbI2 deposition makes this method more environmentally friendly. Outstanding film uniformity across the entire area of 5 cm x 5 cm is confirmed by both large-area compatible characterization methods (electroluminescence and scattered light imaging) and local characterization methods (atomic force microscopy, scanning electron microscopy, photoluminescence mapping, UV-vis, and X-ray diffraction measurements on multiple sample locations), resulting in low solar cell performance decrease upon increasing device area. With the FAPb(I0.85Br0.15)(3) (FA = formamidinium) perovskite layer deposited by this method, champion solar modules show a power conversion efficiency of 14.7% on an active area of 12.0 cm(2) and an outstanding shelf stability (only 3.6% relative power conversion efficiency decay after 3600 h aging). Under continuous operation (1 sun light illumination, maximum power point condition, dry N-2 atmosphere with <5% relative humidity, no encapsulation), the devices show high light-soaking stability corresponding to an average T-80 lifetime of 535 h on the small-area solar cells and 388 h on the solar module.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
lead waste, perovskites, solar modules, stability, upscalability
National Category
Materials Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kau:diva-83178 (URN)10.1002/aenm.201803047 (DOI)000467131300003 ()
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2022-05-25Bibliographically approved
Shi, J., Xu, X., Xia, Y., Chen, R., Hawash, Z., Deribew, D., . . . Scheblykin, I. G. (2019). Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging. Chemistry of Materials, 31(21), 8927-8936
Open this publication in new window or tab >>Photo-Oxidation Reveals H-Aggregates Hidden in Spin-Cast-Conjugated Polymer Films as Observed by Two-Dimensional Polarization Imaging
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 21, p. 8927-8936Article in journal (Refereed) Published
Abstract [en]

Spin-cast intermolecular interactions in conjugated polymer films lead to the formation of excited states delocalized over a few oriented and tightly packed conjugated segments. The optoelectronic properties of conjugated polymers are strongly dependent on the presence of such oriented domains at a nanoscale level. We observe oriented domains as large as several micrometers in size spontaneously formed in spin-cast PBDT-TPD films. Two-dimensional polarization imaging of fresh and photodegraded films showed a much higher visibility of the oriented domains in the degraded samples. We propose that the film is a mixture of two phases with different degrees of chain alignment. The photoluminescence of the more anisotropic phase is more stable against photodegradation in comparison with the less anisotropic phase. Photodegradation predominately quenches photoluminescence of the less anisotropic phase making the oriented domains more visible in the polarization contrasts. Spectral and energy transfer properties of the more oriented phase allowed us to assign it to weakly coupled H-aggregates with the suppressed 0-0 vibronic transition. Stable photoluminescence of H-aggregates in comparison with that of nonaggregated (less oriented) chains may help to understand degradation mechanisms of polymer devices and shows the role of energy transfer in this process. Selective degradation-induced quenching can reveal hidden inhomogeneity of conjugated polymer films.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-75961 (URN)10.1021/acs.chemmater.9b02996 (DOI)000497262500034 ()
Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2020-07-07Bibliographically approved
Qiu, L., Liu, Z., Ono, L. K., Jiang, Y., Son, D.-Y., Hawash, Z., . . . Qi, Y. (2019). Scalable Fabrication of Stable High Efficiency Perovskite Solar Cells and Modules Utilizing Room Temperature Sputtered SnO2 Electron Transport Layer. Advanced Functional Materials, 29(47), Article ID 1806779.
Open this publication in new window or tab >>Scalable Fabrication of Stable High Efficiency Perovskite Solar Cells and Modules Utilizing Room Temperature Sputtered SnO2 Electron Transport Layer
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2019 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 47, article id 1806779Article in journal (Refereed) Published
Abstract [en]

Stability and scalability have become the two main challenges for perovskite solar cells (PSCs) with the research focus in the field advancing toward commercialization. One of the prerequisites to solve these challenges is to develop a cost-effective, uniform, and high quality electron transport layer that is compatible with stable PSCs. Sputtering deposition is widely employed for large area deposition of high quality thin films in the industry. Here the composition, structure, and electronic properties of room temperature sputtered SnO2 are systematically studied. Ar and O-2 are used as the sputtering and reactive gas, respectively, and it is found that a highly oxidizing environment is essential for the formation of high quality SnO2 films. With the optimized structure, SnO2 films with high quality have been prepared. It is demonstrated that PSCs based on the sputtered SnO2 electron transport layer show an efficiency up to 20.2% (stabilized power output of 19.8%) and a T-80 operational lifetime of 625 h. Furthermore, the uniform and thin sputtered SnO2 film with high conductivity is promising for large area solar modules, which show efficiencies over 12% with an aperture area of 22.8 cm(2) fabricated on 5 x 5 cm(2) substrates (geometry fill factor = 91%), and a T-80 operational lifetime of 515 h.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
electron transport layer, perovskite solar modules, scalability, sputtered SnO2, stability
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-83176 (URN)10.1002/adfm.201806779 (DOI)000498650500014 ()
Available from: 2021-02-22 Created: 2021-02-22 Last updated: 2021-03-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9606-3521

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