Templated growth of FASnI3 crystals for efficient tin perovskite solar cells

Tin perovskite solar cells (TPSCs) are rising as the most promising candidates for lead-free PSCs. However, the randomly crystallized tin halide perovskite with a high concentration of defects is still the bottleneck for obtaining high efficiency. Here, we report the pretreatment of FASnI3 (formamidinium, FA) perovskite film by spin-coating a solution of organic halide salt n-propylammonium iodide (PAI) before annealing. It is found that PAI can induce the templated growth of FASnI3 crystals by reconstruction of the intermediate phase, resulting in a highly crystallized FASnI3 film with preferential orientation along the (100) plane and suppressed trap density. Finally, a stabilized efficiency of 11.22% was certified at an accredited test center and the cell is stable, maintaining over 95% of its initial efficiency after 1000 hours of operation at the maximum power point.