Refining Multiscale Heterogeneity in Perovskite Solar Cells via Interfacial Chemistry Homogenization

Abstract Controlling multiscale structural heterogeneities in halide perovskites (HPs) is a key bottleneck to achieving the reproducible high‐performances and longevity of perovskite solar cells (PSCs). A correlative understanding of structural and chemical features at the HP/charge transport layer interface is vital to realizing homogeneous and monolithic crystal matrices. Yet, this is not fully resolved as it requires holistic investigations of the multilayer systems. Herein, the intricate correlations of the interfacial features are resolved by utilizing chemically modified colloidal SnO 2 nanoparticles (NPs) with ethylenediaminetetraacetic acid‐grafted polymeric chitosan (C‐EDTA). This chemical approach drastically enhances colloidal stability of the NPs, thereby manifesting a chemically homogenized surface of the electron transport layer. This promotes a homogeneous crystallization, refining the HP matrix while suppressing the evolution of pinholes and grain boundary grooves at the buried interface. This chemically and structurally refined heterointerface system significantly minimizes the interfacial charge recombination, thereby realizing improved performances of the PSCs with the highest power conversion efficiency of 25.12%. This work provides key insights into the role of structural refinement at the interface benefiting the performances and durability of PSCs − a vital principle in realizing sustainable solar energy platforms.