A Catalyst-like System Enables Efficient Perovskite Solar Cells.

High-quality perovskite films are essential for achieving the high performance of optoelectronic devices. However, solution-processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, we successfully enhanced the microscopic homogeneity of perovskite films by modulating the conversion reaction kinetics using a catalyst-like system generated by a foaming agent. The chemical and structural evolution during this catalytic conversion was revealed by a multimodal synchrotron toolkit with spatial resolutions spanning many length scales. Combining these insights with computational investigations, a cyclic conversion pathway model was developed that yielded exceptional perovskite homogeneity due to enhanced conversion, having a power conversion efficiency of 24.51% for photovoltaic devices. Our work establishes a systematic link between processing of precursor and homogeneity of the perovskite films. This article is protected by copyright. All rights reserved.