Facet-Dependent Control of PbI ₂ 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%).