Controlling competing photochemical reactions stabilizes perovskite solar cells

Motti, Silvia G., Meggiolaro, Daniele, Barker, Alex J., Mosconi, Edoardo, Perini, Carlo Andrea Riccardo, Ball, James M., Gandini, Marina, Kim, Min, De Angelis, Filippo and Petrozza, Annamaria (2019) Controlling competing photochemical reactions stabilizes perovskite solar cells. Nature Photonics, 13 (8), 532-539. (doi:10.1038/s41566-019-0435-1).

Abstract

Metal halide perovskites have become a popular material system for fabricating photovoltaics and various optoelectronic devices. However, long-term reliability must be assured. Instabilities are manifested as light-induced ion migration and segregation, which can lead to material degradation. Discordant reports have shown a beneficial role of ion migration under illumination, leading to defect healing. By combining ab initio simulations with photoluminescence measurements under controlled conditions, we demonstrate that photo-instabilities are related to light-induced formation and annihilation of defects acting as carrier trap states. We show that these phenomena coexist and compete. In particular, long-living carrier traps related to halide defects trigger photoinduced material transformations, driving both processes. Defect formation can be controlled by blocking under-coordinated surface sites, which act as a defect reservoir. By use of a passivation strategy we are thus able to stabilize the perovskite layer, leading to improved optoelectronic material quality and enhanced photostability in solar cells.

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Contributors

Author: Silvia G. Motti

Author: Min Kim

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