Mixed-Bromide Halide Exchange toward Efficient and Stable Carbon-Electrode CsPbBr₃ Solar Cells

CsPbBr3 films with a pinhole-free surface, moderate thickness, and high crystallinity are desired for high-performance and stable perovskite solar cells (PSCs). However, the inherently low solubility of the CsBr precursor material makes it difficult to prepare the desired CsPbBr(3 )film by solution methods. Herein, we demonstrate a mixed-bromide halide exchange method to prepare a CsPbBr3 film through transforming the CsPbIBr2 intermediate phase into CsPbBr3 after spin-coating of MABr/CsBr methanol solution, which avoids the use of low-solubility CsBr. The resulting CsPbBr3 film possesses favorable morphology, high crystallinity, and enlarged work function, which make for improved extraction and transportation of charge carriers, as well as suppressed nonradiative recombination of them. Therefore, the optimized carbon-electrode solar cell yields a high efficiency of 9.36%. And, it also holds the excellent ability to endure humidity attacking since it retained 96% of its initial efficiency after being stored for 60 days in ambient air with the controlled relative humidity at about 40% and the temperature at about 25 degrees C.