Stable tin perovskite solar cells enabled by widening the time window for crystallization

Tin perovskite solar cells (TPSCs) are the most promising candidates for lead-free perovskite solar cells (PSCs). However, the poor crystallization and chemical stability of Sn perovskites are the two challenging issues for further application of TPSCs. Here, we present a strategy to stabilize CH(NH2)2SnI3 (FASnI3) perovskite enabled by an amine complex, CH3NH3I·3CH3NH2, which can hinder the major degradation issue caused by the oxidation of Sn2+ to Sn4+. The resulting Sn perovskite films exhibit enhanced crystallinity and stability in comparison with those made with conventional inorganic SnF2 additives. Finally, the device achieved a higher external quantum efficiency for charge extraction and a power conversion efficiency (PCE) of 9.53%, which maintained more than 90% of the initial efficiency after 1000 h of light soaking under the standard AM 1.5 G solar illumination.