CsPbBr3 perovskite nanoparticles as additive for environmentally stable perovskite solar cells with 20.46% efficiency

The quality of perovskite absorber is one of the most important factors to influence the efficiency and stability of perovskite solar cells (PSCs). However, it is still challenging to obtain perovskite layers with required properties including large grain sizes, better crystallinity, less grain boundaries, and uniform morphology by the current preparation techniques. Here we develop a novel method, where the CsPbBr3 nanoparticles (NPs) are introduced into the chlorobenzene anti-solvent to improve the MAPbI3 film quality in terms of film structure, morphology and crystallinity, leading to reduced charge recombination and improved charge transfer. CsPbBr3 NPs play a role as nucleation centers in the growth process of perovskite films, and CsPbBr3 NPs also induce a passivation layer Cs1-yMAyPbI3-xBrx on the top of perovskite layer. The charge transport and power conversion efficiency (PCE) are improved due to the introduction of CsPbBr3 NPs. A champion PCE of 20.46% is obtained for the PSCs based on high quality perovskite film prepared with CsPbBr3 NPs. In addition, the PSCs with CsPbBr3 NPs also exhibit improved stability. This work not only demonstrates a novel strategy to prepare high quality perovskite films for PSCs with high efficiency and stability, but also provides important insight in the growth mechanisms of perovskite films toward high crystallinity and less defects.