Mitigation\nof Self-p-Doping and Off-Centering Effect\nin Tin Perovskite via Strontium Doping

Tin-based perovskite solar cells offer a less toxic alternative\nto their lead-based counterparts. Despite their promising optoelectronic\nproperties, their performances still lag behind, with the highest\npower conversion efficiencies reaching around 15%. This efficiency\nlimitation arises primarily from electronic defects leading to self-p-doping\nand stereochemical activity of the Sn(II) ion, which distorts the\natomic arrangement in the material. In this study, we investigate\nthe effect of strontium doping in tin-based perovskite on the distortion\nof the material’s structure and its optoelectronic properties.\nUsing a combination of Density Functional Theory calculations and\nexperiments, we demonstrate that strontium doping reduces p-doping\nand structural strain. This approach improves the efficiency from\n6.3% in undoped devices to 7.5% in doped devices without relying on\ndimethyl sulfoxide, a harmful solvent for tin-based perovskites. This\nmethod could enable precise control of tin off-centering and self-p-doping,\nadvancing the development of efficient and stable tin perovskite solar\ncells.