Advances in cesium lead iodide perovskite solar cells: Processing science matters

The prevailing perovskite solar cells (PSCs) employ hybrid organic–inorganic halide perovskites as light absorbers, but these materials exhibit relatively poor environmental stability, which potentially hinders the practical deployment of PSCs. One important strategy to address this issue is replacing the volatile and hygroscopic organic cations with inorganic cesium cations in the crystal structure, forming all-inorganic halide perovskites. In this context, CsPbI₃ perovskite is drawing phenomenal attention, primarily because it exhibits an ideal bandgap of 1.7 eV for the use in tandem solar cells, and it shows significantly enhanced thermal stability that is the key to the long-term device operation. Within only half a decade, the power conversion efficiency (PCE) of CsPbI₃ PSCs has ramped beyond 20%, which has been driven by inventions of numerous processing methods for high-quality CsPbI₃ perovskite thin films. These methods are broadly classified into three categories: vapor deposition, nanocrystals assembly, and solution deposition. Herein we present a systematic review on these methods and related materials sciences. In particular, we comprehensively discuss the dimethylammonium-additive-based solution deposition, which has resulted into the best-performing CsPbI₃ PSCs. We also present the challenges and prospects on future research towards the realization of the full potential of CsPbI₃ PSCs.