Performance Optimization of Semi‐Transparent CsPbBr 3 Perovskite Solar Cells via Synergistic Dual‐Function Regulation by BaCl 2

ABSTRACT CsPbBr 3 perovskite exhibits considerable potential for application in semi‐transparent perovskite solar cells (PSCs) due to its excellent thermal stability and suitable optical bandgap. However, several inherent drawbacks such as rapid carrier recombination rate and high density of crystal defects hinder the further improvement of its photoelectric efficiency. This work proposes an ion substitution modification strategy, wherein BaCl 2 is employed as a doping agent to incorporate Ba 2+ into CsPbBr 3 . Experimental results indicate that Ba 2+ can effectively regulate the lattice parameters of CsPbBr 3 , thereby significantly increasing the grain size and reducing the concentration of vacancy defects. Meanwhile, the unique ionic radius and electronegativity of Ba 2+ enable the optimization of the band structure of CsPbBr 3 , which not only lowers the energy level barrier but also remarkably suppresses non‐radiative recombination. The efficiency of semi‐transparent CsPbBr 3 PSCs fabricated via Ba 2+ substitution modification is increased from 6.20% to 7.24%. In addition, we employ V 2 O 5 to optimize the interface properties in semi‐transparent CsPbBr 3 PSCs, thereby further enhancing the device performance to 7.54%. The modified devices can retain over 85% of their initial efficiency under humidity and thermal stress conditions for 1500 h, demonstrating outstanding long‐term operational stability.