Aqueous Synthesis of α-Cs_xFA_1–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 Cs x FA 1– x PbI 3 (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.