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(NH 2 ) 2 SnI 3 (FASnI 3 ) perovskite enabled by an amine complex, CH 3 NH 3 I·3CH 3 NH 2 , which can hinder the major degradation issue caused by the oxidation of Sn 2+ to Sn 4+ . The resulting Sn perovskite films exhibit enhanced crystallinity and stability in comparison with those made with conventional inorganic SnF 2 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.