2020/09/30 by Davide Raffaele Ceratti, Ceratti, D R, Ayala V. Cohen +26
Engineering · Materials Science · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Perovskite Materials and Applications #Solid-state spectroscopy and crystallography
paper · pdf · doi:10.48550/arxiv.2009.14617
openalex publication_date 2020/09/30 · openalex created_date 2020/10/08 · openalex updated_date 2026/07/28
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.