Solvent engineering for efficient inverted perovskite solar cells based on inorganic CsPbI2Br light absorber

Inorganic cesium lead halide perovskites, as alternative light absorbers for organic−inorganic hybrid perovskites, have attracted more and more attentions due to their superb thermal stability for photovoltaic applications. However, the device performance, as reported to date, is dispirited as it is still a challenge to prepare inorganic perovskite films with both sufficient absorbance and high quality. Here, solvent engineering is conducted, and solvent composition is found largely influence the crystallization progress and film morphology. Combined with anti-solvent-extraction technology, homogenous and pinhole-free CsPbI2Br films have been prepared with optimized solvent of DMF/DMSO mixture with the volume ratio of 3:2. The inverted planar device with a 410 nm-thick CsPbI2Br absorber achieves a power conversion efficiency of 9.14%. Furthermore, the as-prepared perovskite and its based device exhibit good stability under high temperature stress and continuous light soaking at maximum power point tracking conditions (100 mW cm−2, 500 h).