The pursuit of stability in halide perovskites: the monovalent cation and the key for surface and bulk self-repair

D R Ceratti; A V Cohen; R Tenne; Y Rakita; L Snarski; L Cremonesi; I Goldian; I Kaplan-Ashiri; T Bendikov; V Kalchenko; M Elbaum; M A C Potenza; L Kronik; G Hodes; D Cahen

arXiv · 2009.14617

The pursuit of stability in halide perovskites: the monovalent cation and the key for surface and bulk self-repair

D R Ceratti·A V Cohen·R Tenne·Y Rakita·L Snarski·L Cremonesi·I Goldian·I Kaplan-Ashiri·T Bendikov·V Kalchenko·M Elbaum·M A C Potenza·L Kronik·G Hodes·D Cahen

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Abstract

We find significant differences between degradation and healing at the surface or in the bulk for each of the different APbBr3 single crystals (A=CH3NH3+, methylammonium (MA); HC(NH2)2+, formamidinium (FA); and cesium, Cs+). Using 1- and 2-photon microscopy and photobleaching we conclude that kinetics dominate the surface, and thermodynamics the bulk stability. Fluorescence-lifetime imaging microscopy, as well as results from several other methods, relate the (damaged) state of the halide perovskite (HaP) after photobleaching to its modified optical and electronic properties. The A cation type strongly influences both the kinetics and the thermodynamics of recovery and degradation: FA heals best the bulk material with faster self-healing; Cs+ protects the surface best, being the least volatile of the A cations and possibly through O-passivation; MA passivates defects via methylamine from photo-dissociation, which binds to Pb2+. DFT simulations not only provide insight into the latter conclusion, but also show the importance and stability of the Br3- defect. These results rationalize the use of mixed A-cation materials for optimizing both solar cell stability and overall performance of HaP-based devices, and provide a basis for designing new HaP variants.

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D R Ceratti, A V Cohen, R Tenne, Y Rakita, L Snarski, L Cremonesi, I Goldian, I Kaplan-Ashiri, T Bendikov, V Kalchenko, M Elbaum, M A C Potenza, L Kronik, G Hodes, D Cahen. 2020-09-30. The pursuit of stability in halide perovskites: the monovalent cation and the key for surface and bulk self-repair. https://arxiv.org/abs/2009.14617

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