Aqueous Synthesis of α-CsxFA1–xPbI3 Microcrystals for Efficient Perovskite Solar Cells

Integrating cesium (Cs) into perovskite layers significantly enhances the stability of perovskite solar cells (PSCs), which is a critical aspect for achieving high efficiency. However, the elemental and phase segregation, caused by the inhomogeneous distribution of Cs within the perovskite film, poses a risk to the device’s lifetime. To address this issue, we present an innovative aqueous synthesis method for CsxFA1–xPbI3 (CsFA) microcrystals as precursors to perovskite thin films. These synthesized microcrystals ensure uniform cesium distribution across the perovskite grains, acting as a 3D scaffold for the crystallization process. This scaffold serves as a template, facilitating a homogeneous Cs distribution within the perovskite film. Utilizing these CsFA microcrystals, we achieved a maximum power conversion efficiency (PCE) of 23.70%, with the devices maintaining 96% of their initial PCE after 600 h in ambient conditions. Our innovative approach facilitates the mass production of high-purity CsFA microcrystals from cost-effective, low-purity starting materials, which is conducive to facile application for further commercialization.