Nanoparticle-induced fast nucleation of pinhole-free PbI2 film for ambient-processed highly-efficient perovskite solar cell

Fully ambient, low temperature-processed, and high-performance perovskite solar cells (PSCs) fabricated with sequential deposition method (SDM) are especially attractive for future commercialization. However, it is extremely difficult as uncontrollable crystallization of PbI2 upon deposition is usually induced by moisture under atmospheric conditions. Here, we report a nanoparticle-induced fast nucleation (NIFN) method to improve the quality of fully ambient-processed PbI2 layer. In particular, ZnO nanoparticles (NPs) are added into the lead iodide solution as growth controlling agents to obtain pinhole-free PbI2 layer, leading to pinhole-free MAPbI3 (methylammonium lead iodide) layer. As compared to the control devices, the devices made of pinhole-free MAPbI3 film show an improvement of power conversion efficiency (PCE) over 20%. Moreover, an ambient-processed PSC by using this simple method shows a record PCE up to 18.3%. Our work not only reveals the origin of the morphology PbI2 and its effect on MAPbI3 film formation in ambient air, but demonstrates a simple and unique method to boost ambient-processed high-performance PCSs for potential industrial use.