Surface-Controlled Oriented Growth of FASnI3 Crystals for Efficient Lead-free Perovskite Solar Cells

Tin-based perovskites with narrow band gap and high carrier mobility are promising candidates for the preparation of efficient lead-free perovskite solar cells (PSCs). However, the poor crystallization of tin-based perovskite films with unfavorable defects and rough morphology is still the biggest challenge to achieve high power conversion efficiency. In this work, we reveal the surface-controlled growth of FASnI3 perovskite films, and then precisely control the crystallization process by reducing the surface energy of the solution-air surface with a tailor-made pentafluorophen-oxyethylammonium iodide (FOEI). The demonstrated strategy enabled us to achieve highly oriented and smooth FASnI3-FOEI films with lower defect density and longer lifetime of charge carriers. A certificated efficiency of 10.16% for tin-based PSCs was obtained from an accredited institute.