Broadband photoresponse enhancement in tin-based perovskites via CF3PEA <b>+</b> A-site doping

Eco-friendly tin-based perovskites have been promising lead-free alternatives for optoelectronic applications, yet their performance is limited by rapid crystallization and poor crystal quality. Here, we utilize 2-[4-(trifluoromethyl)phenyl]ethylammonium (CF3PEA+) doping at the A-site to simultaneously enhance the stability and optoelectronic properties of FASnI3 while preserving its three-dimensional structure. We demonstrate that optimal CF3PEA+ doping (6%) significantly slows down crystallization kinetics, suppresses Sn2+ oxidation, reduces deep-traps, and improves charge carrier mobility of the perovskite film. Compared to undoped films, the doped films exhibit significant improvements in charge transport and photoresponsivity (from 0.272 to 1.52 A/W at 637 nm) across 350–980 nm, outperforming phenethylammonium (PEA+)-doped counterparts. Spectroscopic studies reveal that these enhancements originate from strong chemical interactions between the CF3PEA+ and the perovskite cations. This work provides important insights into rational A-site engineering for high-performance tin-based optoelectronic devices.