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 PbI 2 (S-PbI 2 ) with tunable morphology. Further, facet-dependent PbI 2 colloid regulation is demonstrated, and the relations among the morphology of the PbI 2 crystal, features of PbI 2 colloids, the morphology of the PbI 2 film, and the photovoltaic performance of MAPbI 3 are established. The PSCs based on 10% S-PbI 2 exhibited a best PCE of 20.22% with improved device reproducibility and hysteresis index compared to that using commercial PbI 2 (∼18%).