Ceratti DR, Cohen AV, Tenne R, Rakita Y, Snarski L, Jasti NP, Cremonesi L, Cohen R, Weitman M, Rosenhek-Goldian I, Kaplan-Ashiri I, Bendikov T, Kalchenko V, Elbaum M, Potenza MAC, Kronik L, Hodes G, Cahen D. The pursuit of stability in halide perovskites: the monovalent cation and the key for surface and bulk self-healing.
MATERIALS HORIZONS 2021;
8:1570-1586. [PMID:
34846465 DOI:
10.1039/d1mh00006c]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
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 provide insight into the passivating role of MA, and also indicate the importance of the Br3- defect as well as predicts its stability. The occurrence and rate of self-healing are suggested to explain the low effective defect density in the HaPs and through this, their excellent performance. 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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