A flowing liquid phase induces the crystallization processes of cesium lead triiodide for 21.85%-efficiency solar cells and low-energy loss

Abstract

Solution-processing of perovskite layers is crucial for the production of high-performance electronics and optoelectronics. The annealing conditions alter the cost of the final production. Therefore, seeking for a mild preparation processing and achieving a high-quality perovskite film are important. Here, we proposed an effective flowing liquid phase to induce the crystallization of perovskite grains. On the one hand, the flowing liquid phase changed the reactive paths from the solid to liquid, which lowered the reactive energy barrier and energy demands, providing a mild annealing condition. On the other hand, the reaction based liquid phase can proceed more adequately, yielding a more uniform thin film. As a result, a high efficiency of 21.85% has been achieved, with a low V_oc deficiency of 0.47 V. As well, high-quality CsPbI₃ contributed to high stability of the assembled device.