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.