TFSI ion migration in perovskite solar cells: beneficial or detrimental?

Cristina Momblona^a^,^b, Nadja Klipfel^b, Albertus Adrian Sutanto^b, Mounir Mensi^b, Cansu Igci^b, Klaus Leifer^b, Keith Brooks^b, Sachin Kinge^c, Cristina Roldán-Carmona^b^,^d, Paul J. Dyson^e, Mohammad Khaja Nazeeruddin^b

^aInstituto de Ciencia de los Materiales de la Universidad de Valencia (ICMUV), 46980, Paterna, Valencia, Spain

^bGroup for Molecular Engineering of Functional Material, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Switzerland

^cToyota Motor Europe, Hoge Wei 33, B-1930 Zaventem, Belgium

^dInstituto de Ciencia Molecular, Universidad de Valencia, C/ Catedrático J. Beltrán 2, 46980 Paterna (Valencia), Spain.

^eLaboratoire de Chimie organométallique et médicinale, École Polytechnique Fédérale de Lausanne, Switzerland

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)

València, Spain, 2022 May 19th - 25th

Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson

Poster, Cristina Momblona, 199
Publication date: 20th April 2022

The chemical doping of the hole transport material N²,N²,N^2′,N^2′,N⁷,N⁷,N^7′,N^7′-octakis(4-methoxyphenyl)-9,9′-spirobi[9H-fluorene]-2,2′,7,7′-tetramine (spiro-OMeTAD) is one of the main factors that influence the device stability in perovskite solar cells (PSCs).¹ It is known that the Li ions from the spiroOMeTAD dopant, bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), easily migrate through the device² but little attention has been paid to the counterion or other spiroOMeTAD´s dopant. In this work,³ we studied the TFSI^- migration from the spiroOMeTAD layer placed underneath a co-evaporated MAPI film in p-i-n solar cells to the perovskite surface. We found that the TFSI ions migrate along the perovskite boundaries and the migration is dependent on the dopant nature being the process from CoTFSI faster than from LITFSI. Contrary to belief, the anion migration is beneficial for the device performance and stability: they passivate the Pb²⁺perovskite defects and the solar cells retain 90% of their initial performance after 1600 h under continuous light illumination.

References:

[1] Berhe, T. A.; Su, W.-N.; Chen, C.-H.; Pan, C.-J.; Cheng, J.-H.; Chen, H.-M.; Tsai, M.-C.; Chen, L.-Y. ; Dubale, A. A.; Hwang, B.-J. Organometal halide perovskite solar cells: degradation and stability. Energy Environ. Sci., 2016, 9, 323-356.

[2] Li, Z.; Xiao, C.; Yang, Y.; Harvey, S. P.; Kim, D. H.; Christians, J. A.; Yang, M.; Schulz, P.; Nanayakkara, S. U.; Jiang, C.-S.; Luther, J. M.; Berry, J. J.; Beard, M. C.; Al-Jassim, M. M.; Zhu, K. Extrinsic ion migration in perovskite solar cells. Energy Environ. Sci., 2017, 10, 1234-1242.

[3] Klipfel, N.; Kanda, H.; Sutanto, A. A.; Mensi, M.; Igci, C.; Leifer, K.; Brooks, K.; Kinge, S.; Roldán-Carmona, C.; Momblona, C.; Dyson, P. J.; Nazeeruddin, M. K. Mechanistic insights into the role of the bis(trifluoromethanesulfonyl)imide ion in coevaporated p-i-n perovskite solar cells. ACS Appl. Mater. Interfaces. 2021, 13, 52450-52460.

Acknowledgements:

The authors acknowledge Professor Raffaella Buonsanti for the use of the Fluorolog system. C. M. acknowledge the Generalitat Valenciana (Spain) for the CDEIGENT 2021. N.K. and C.M. thank the European Union’s Horizon 2020 Research and Innovation Program Nos. 764787 and 763977. H.K. acknowledges the support of the H2020 Program for Solar-ERANET funding of the BOBTANDEM (2019–2022). A.A.S. and C.I. acknowledge the Swiss National Science Foundation (SNSF) funding through Synergia Grant EPISODE (Grant No. CRSII5_171000). C.R.-C. and C.M. thank the Project German Research Foundation (DFG) (Project Number 424101351)─Swiss National Foundation (SNF) (200021E_186390)

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