Issue 11, 2020

Suppressed phase transition of a 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 a humid atmosphere. Here, we report that partial substitution of cesium by the potassium or rubidium element can effectively improve the 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− octahedron distortion and accelerates the phase transition, can be effectively alleviated by 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 a much lower energy barrier in pristine CsPbI3. Based on these improvements, the doped perovskites remained in the major α-phase after direct exposure to ambient air (RH ∼ 30%) for 5 hours, while pristine CsPbI3 showed an irreversible degradation. With the clarified mechanism of enhanced phase stability of Rb/K incorporation, we suggest such a doping method as a promising strategy to be widely applied in the field of photovoltaic devices.

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

Supplementary files

Article information

Article type
Paper
Submitted
12 Des. 2019
Accepted
08 Feb. 2020
First published
10 Feb. 2020

Nanoscale, 2020,12, 6571-6581

Suppressed phase transition of a 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, 12, 6571 DOI: 10.1039/C9NR10548D

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