Dynamics of Ionic Additive Passivation in Perovskite Solar Cells
Matthias Diethelm a, Henry Snaith a
a Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK, Parks Road, Oxford, United Kingdom
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
, Matthias Diethelm, presentation 289
DOI: https://doi.org/10.29363/nanoge.hopv.2022.289
Publication date: 20th April 2022

After an extraordinary rise in power conversion efficiency, perovskite thin film technology is reaching the performance of silicon photovoltaics, and tandem applications such as perovskite-on-silicon are promising candidates to go well beyond 30 % efficiency. Regarding commercialization, however, understanding possible degradation mechanisms is mandatory, given that silicon technology guarantees an efficiency loss of less than 20 % in 25 years. Ionic point defects and static deep traps - mobilised by high temperature, irradiation and external electric fields - contribute to the intrinsic instability of perovskite solar cells. Several strategies to passivate defects and suppress their dynamics are used, with arguably the most promising being ionic additives intermixed into the active layer. This approach has led to stability records while maintaining high efficiencies above 20 %. Recent research indicates a lack of in-depth understanding of the actual defect passivation effect and calls for suitable characterization methods. Dynamic processes due to mobile ions, trap development or phase segregation within the perovskite layer are well studied individually, but their interplay has still to be further unravelled. To establish a convincing picture of the passivating effects additives have on defects under operation conditions, typically used electrical and optical methods are combined with fast logarithmic (µs to s) electric pulses. While the solar cell with and without additive [1] is aged at high temperatures and full-spectrum simulated sunlight, fast JV measurement track hysteresis evolution, photoluminescence measurement provide information on phase segregation [2] and the quasi-Fermi level splitting [3], time-resolved photoluminescence tracks charge carrier lifetime as a measure for deep trap Shockley-Read-Hall recombination, and impedance spectroscopy at lower frequencies is a measure for EDL formation and recombination currents. The fast logarithmic (µs to s) electric pulses reveal the ageing behaviour of the dynamic processes and combine the results of the other characterisation methods. The method is explained and first results are shown.

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