Light Soaking Effects and Passivation in Metal Halide Perovskites
Bernard Wenger a, Godding Julian a, Snaith Henry a
a University of Oxford, Department of Physics, Clarendon Laboratory, Parks Road, Oxford, OX13PU, UK
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Bernard Wenger, 239
Publication date: 11th February 2019

Lead halide perovskites show impressive optoelectronic properties as demonstrated by their high radiative efficiencies and power conversion efficiencies in photovoltaic devices surpassing 20%. Since this is rather exceptional for materials synthesized directly from precursors in solution with simple coating techniques, the quality of semiconducting lead halide perovskites has sometimes been attributed to their “defect tolerance”. However, substantial improvements of radiative efficiency can be obtained by various post-deposition treatments. The effectiveness of such passivation techniques demonstrates clearly that these materials do suffer from defects and, moreover, that these defects are likely to be localised at the surface of grains in polycrystalline films.

We present an experimental study on the peculiar form of passivation achieved via light -soaking, also known as photo-brightening. From a thorough analysis of the literature and our own experiments, we propose a comprehensive mechanism for this effect and discuss the parameters influencing its occurrence.

Finally, based on this knowledge, we devise a new passivation route that mimics the photo-brightening effect without exposure to light or humid and/or oxygen containing atmosphere. We present thin films with improved photoluminescence efficiencies and solar cells with enhanced Voc and power conversion efficiencies.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 706552

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