Suppression of surface recombination in tin-halide perovskite solar cells via Lewis base post-treatment

摘要

Tin perovskite solar cells (PSCs) showed the most promise to replace the more toxic lead-based PSCs. However, the efficiency of tin-based PSCs falls short of that of lead-based PSCs by a big margin, as a result of low open-circuit voltage. This is due to the tendency of Sn~(2+) to oxidize into Sn~(4+) in the presence of air together with the formation of defects and traps caused by the fast crystallization of tin perovskite materials. Here, we performed post-treatment of tin perovskite layer with Lewis base to suppress the recombination reaction in tin halide PSCs resulting in efficiencies more than 10%, which is the highest reported efficiency to date for pure tin-halide PSCs. Upon analyzing the X-ray photoelectron spectroscopy and impedance spectroscopy data, we came to the conclusion that the amine-group bonded the under-coordinated perovskite, passivating the dangling bonds and defects resulting in suppressed charge carrier recombination. This also has the effect of prolonged lifetime and higher charge carrier mobility. Our findings will provide the groundwork for improving the efficiency of pure tin halide PSCs to compete with that of lead-based PSCs by simple post-treatment with organic molecules.