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Suppressed phase transition of Rb/K incorporated inorganic perovskite with a water-repelling surface

Abstract

Inorganic cesium lead halide (CsPbI3) is a promising candidate for next-generation photovoltaic devices but photoactive α-phase CsPbI3 can rapidly transform to non-photoactive yellow δ-CsPbI3 in humid atmosphere. Here, we report that partial substitution of cesium by potassium or rubidium element can effectively improve phase stability against moisture by forming a water-repelling surface layer with Rb/K segregation. Using density functional theory, we found that the water-induced polarization, which triggers the PbI62- octahedra distortion and accelerate the phase transition, can be effectively alleviated after incorporating Rb/K elements. Further exploration of transition states suggests that Rb/K doped surface layers result in a higher activation barrier for water penetration. The electronic structure analysis further reveals that the barrier enhancement originates from the absence of the participation of inner 5p electrons in Rb/K-H2O binding, which induces much low energy barrier in pristine CsPbI3. Based on these improvements, doped perovskites remained major α-phase after direct exposition to ambient airs (RH~30%) for 5 hours while pristine CsPbI3 showed an irreversible degradation. With clarified mechanism of enhanced phase stability of Rb/K incorporation, we suggested such doping method as a promising strategy to be widely applied in the field of photovoltaic devices.

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Supplementary files

Article information


Submitted
12 Dec 2019
Accepted
08 Feb 2020
First published
10 Feb 2020

Nanoscale, 2020, Accepted Manuscript
Article type
Paper

Suppressed phase transition of Rb/K incorporated inorganic perovskite with a water-repelling surface

M. Zhang, X. Chen, J. Xiao, M. Tai, D. Legut, J. Shi, J. Qu, Q. Zhang, X. Li, L. Chen, R. Zhang, H. Lin and Q. Zhang, Nanoscale, 2020, Accepted Manuscript , DOI: 10.1039/C9NR10548D

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