Facet-Dependent Control of PbI2 Colloids for over 20% Efficient Perovskite Solar Cells

Organic–inorganic hybrid perovskite-based solar cells (PSCs) have made impressive progress during the past few years, and record power conversion efficiency over 23% has been achieved. However, for solution-processed perovskite films, one of the major challenges for film quality improvement is the lack of a regulation strategy for the colloids in the precursor solution. Here, we demonstrate facet-dependent colloid engineering to adjust the quality of a perovskite film and its photovoltaic performance. This is realized by the development of a facet passivation strategy to synthesize PbI2 (S-PbI2) with tunable morphology. Further, facet-dependent PbI2 colloid regulation is demonstrated, and the relations among the morphology of the PbI2 crystal, features of PbI2 colloids, the morphology of the PbI2 film, and the photovoltaic performance of MAPbI3 are established. The PSCs based on 10% S-PbI2 exhibited a best PCE of 20.22% with improved device reproducibility and hysteresis index compared to that using commercial PbI2 (∼18%).