Authors: Xianggang Chen, Huirong Peng, Xiaoxu Sun, Longfei Yan, Xuzheng Feng, Shuyuan Fan, Rui Jia, Songyuan Dai, Xiaolong Li, Xingmin Zhang, Xing Li, Molang Cai
Published: 2025-03-11
Source: Full article
AbstractCesium lead iodide (CsPbI₃) is a promising material for semitransparent perovskite solar cells (ST‐PSCs) in building‐integrated photovoltaics (BIPV) due to its favorable bandgap and thermal stability. However, the phase instability of CsPbI₃ limits its device performance. Developing a simple strategy to regulate the phase transition is essential for enhancing both device efficiency and stability. In this study, synchrotron‐based grazing‐incidence wide‐angle X‐ray scattering and in situ X‐ray diffraction results revealed that adding HBr promotes the formation of γ‐CsPbI₃ at low temperatures. Upon annealing at 100 C, this γ‐phase partially converts to α‐CsPbI₃, resulting in a mixed‐phase film. This mixed‐phase film effectively mitigates substrate strain caused by mismatched thermal expansion coefficients and strain generated during phase transitions. Moreover, the mixed‐phase CsPbI₃ films exhibit a pinhole‐free morphology with reduced defect density, leading to enhanced moisture stability under ≈85% relative humidity. Consequently, the mixed‐phase CsPbI₃‐based ST‐PSC achieved a remarkable power conversion efficiency (PCE) of 19.89% and retained 90.89% of its initial PCE after 500 h of continuous illumination.