Suppressed oxidation of tin perovskite by Catechin for eco-friendly indoor photovoltaics

While fabricating tin (Sn)-based perovskite solar cells (PSCs), it is beneficial to tune the bandgap of the perovskite absorber layer by changing the ratio of halide ions, for improved performance. However, oxidation limits the power conversion efficiency (PCE) [Jeon et al., Nat. Mater. 13, 897 (2014); Ke et al., ACS Energy Lett. 3, 1470 (2018); Yang et al., Adv. Energy Mater. 10, 1902584 (2020); Baig et al., Optik 170, 463 (2018)]. Herein, we introduced Catechin into the perovskite layer to suppress oxidation. We achieved FA0.75MA0.25SnI2Br thin films with a low Sn4+ ratio. Owing to Catechin doping, devices yielded an average PCE of 5.45% and a Champion PCE of 6.02%, higher than the average PCE of 4.29% for the device without Catechin doping. Furthermore, the stability of the doped device improved. It also exhibited dramatic performance when exposed to indoor lighting with the maximum PCE approaching 12.81% under 1000 lx. This work further advances the field of lead-free PSCs and the potential of indoor photovoltaics.