Electron Blocking 2D Perovskite In Highly Efficient (18.5%) Hole-Selective Layer-Free Perovskite Solar Cells Using Low-Temperature Processed Carbon Electrode

Salma Zouhair^a^,^b, So-Min Yoo^c, Dmitry Bogachuk^a, Jan Philipp Herterich^a^,^d, Jaekeun Lim^a, Uli Würfel^a^,^d, Adil Chahboun^b, Mohammad Khaja Nazeeruddin^c, Andreas Hinsch^a, Lukas Wagner^a, Hobeom Kim^c

^aFraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, 79110 Freiburg, Germany, Freiburg, Germany

^bThin films and nanomaterials laboratory, Faculty of Sciences and Techniques (FST), Tangier, Morocco

^cInstitute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) Sion, Switzerland

^dFreiburg Materials Research Center FMF, Albert-Ludwigs-University Freiburg, DE, Stefan-Meier-Straße, 25, Freiburg im Breisgau, Germany

NIPHO
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO22)

Online, Spain, 2022 February 14th - 15th

Organizers: Giulia Grancini, Mónica Lira-Cantú and Silvia Colella

Contributed talk, Salma Zouhair, presentation 011
DOI: https://doi.org/10.29363/nanoge.nipho.2022.011
Publication date: 11th November 2021

Perovskite solar cells (PSC) with printable carbon-graphite back electrodes are promising candidates for commercialization of perovskite devices thanks to their low processing costs and extraordinary stability. However, due to the lack of hole selective layers, this device architecture still suffers from severe performance losses at the perovskite/carbon electrode interface. ^[1]

Following recent advances in interface passivation by 2D perovskites,^[2] we report on a novel approach to employ 2D perovskites as an electron blocking hole conducting layer for an efficient surface passivation of the perovskite absorber successfully enhacing the quality of the corresponding interface with the carbon back electrode. This was achieved through incorporating an octylammonium iodide (OAI) salt on a FAPbI₃ 3D perovskite absorber. Through X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ultraviolet photoelectron spectroscopy (UPS) and microscopically resolved photoluminescence (PL) microscopy measurements we confirm the formation of a high band gap 2D perovskite layer at the interface between the perovskite and the carbon electrode which is found to behave as an electron blocking layer. We find that the 2D passivation layer does not only increase the steady state photovoltage by 65 mV, but also the fill factor (FF) by 10% absolute. This leads to a champion device yielding a power conversion efficiency (PCE) of 18.5%, which is to the best of our knowledge, the highest reported for HSL-free perovskite solar cells using low temperature carbon back electrodes. Comparative illumination dependent J_SC-V_OC analysis and electrochemical impedance spectroscopy (EIS) measurements were carried out to gain more insights on the reduced interfacial recombination losses. We demonstrate minimized interfacial resistance and non-radiative recombination limitations. Maximum power point tracking (MPPT) measurements demonstrated that the 2D perovskite electron blocking layer also led to an improved device stability, with the hole selective layer-free carbon electrode base PSC still performing at over 82% of its initial normalized efficiency after 500 hours of continuous 1-sun illumination.

We thus highlight the tremendous potential of 2D perovskites in enhancing the photovoltaic performance and stability of hole selective layer free perovskite solar cells. We demonstrate its electron blocking characteristic which we believe would help pave the way for the future practical development of fully printable carbon based perovskite devices.

References:

[1] Wagner, L.; Qiu, C.; Unmüssig, M.; Bogachuk, D.; Mastroianni, S.; Würfel, U.; Hu, Y.; Han, H.; Hinsch, A. A 2D Model For Interfacial Recombination In Mesoscopic Perovskite Solar Cells With Printed Back Contact. Solar RRL 2020, 5, 2000595.

[2] Kim, H.; Pei, M.; Lee, Y.; Sutanto, A.; Paek, S.; Queloz, V.; Huckaba, A.; Cho, K.; Yun, H.; Yang, H.; Nazeeruddin, M. Self‐Crystallized Multifunctional 2D Perovskite for Efficient and Stable Perovskite Solar Cells. Advanced Functional Materials. 2020, 30, 1910620.

Acknowledgements:

This work was partially funded by the project UNIQUE, supported under the umbrella of SOLARERA.NET. Cofunded by ANR, PtJ, MIUR, MINECOAEI, and SWEA. SOLAR-ERA.NET was supported by the European Commission within the EU Framework Programme for Research and Innovation HORIZON 2020 (Cofund ERA-NET Action, no. 691664).

S. Z. gratefully acknowledges the Ph.D. scholarship support of the German academic exchange service (DAAD).

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