Lattice Modulation of Alkali Metal Cations Doped Cs1−xRxPbBr3 Halides for Inorganic Perovskite Solar Cells

The crystal structure of cesium lead halide (CsPbX 3 , X = I, Br, Cl) determines its charge-carrier trap state and solar-to-electrical conversion ability in inorganic perovskite solar cells (PSCs). Here, the compositional engineering of inorganic CsPbBr 3 perovskite by means of doping with various alkali metal cations is studied. The lattice dimensions and energy levels of Cs 1- x R x PbBr 3 (R = Li, Na, K, Rb, x = 0–1) halides are optimized by tuning Cs/R ratio. Arising from promoting effects of alkali metal cations doped perovskite halides such as lattice shrink, crystallized dynamics, and electrical-energy distribution, a maximum power conversion efficiency as high as 9.86% is achieved for hole transporting layer-free Cs 0.91 Rb 0.09 PbBr 3 tailored solar cell owing to the suppressed non-radiative losses and radiative recombination. Furthermore, the all-inorganic Cs 0.91 Rb 0.09 PbBr 3 solar cell without encapsulation remains 97% of initial efficiency when suffering persistent attack by 80% RH in air atmosphere over 700 h, which is in comparable with state-of-the-art organic–inorganic hybrid and all-inorganic PSC devices. Employing alkali metal cations to modulate perovskite layers provide new opportunities of making high-performance inorganic PSC platforms.