Deciphering the Role of Alkali Metals in Perovskite Solar Cells: Beyond High Photovoltage
Clara Aranda a b, Monika Rai b, Agustin Alvarez c, Chittaranjan Das b, Michael Saliba a b
a Forschungszentrum Jülich GmbH, Cauerstraße, 1, Erlangen, Germany
b Institute for Photovoltaics (ipv), University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany
c Institute of Advanced Materials (INAM), Universitat Jaume I, Av. Sos Baynat s/n, 12071 Castelló, Spain
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, Clara Aranda, 224
Publication date: 20th April 2022

The consequences of ionic migration represent one of the major bottlenecks in the achievement of real large-scale and stable commercial perovskite solar cells. These consequences include slow kinetic phenomena such as hysteretic responses, coupled with light-induced accumulation capacitance, directly affecting photovoltage values.1 As dopants in the bulk or at the interfaces, alkali metals have proven to be good allies in the race to mitigate the perovskite ionic migration or its effects.2 However, the exact role of the alkali in each case still need to be clarified. Regarding interfacial effects, one of the strategies that has proven to be very beneficial, consists in increasing the cation density at the charge accumulation zone at the ESL/perovskite interface.3 In this work, we have gone a step further by systematically analysing the effects of variation in extrinsic cation density in the photovoltaic performance and stability of wide bandgap perovskite solar cells. Using three different alkali metals as doping agents at the interface, we have found that the beneficial effects can be more bulk-directed or more related to interfacial processes, depending on the ionic size of the dopant. The analysis through impedance spectroscopy and time-resolved photoluminescence, among others, clarify the reasons why an outstanding photovoltage > 1.64 V is achieved, together with an improved stability of the PSCs.

C.A. and M.S.acknowledge to the Helmholtz Young Investigator Group FRONTRUNNER. A.A acknowledge funding from the European Union’sHorizon 2020 MSCA Innovative Training Network, undergrant agreement No. 764787

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