Passivating Grain Boundary Defects with Tris(hydroxymethyl)aminomethane to Achieve Efficient and Stable Tin-Based Perovskite Solar Cells

Abstract

Although tin (Sn)-based perovskite is regarded as a good substitute for a lead-based analogue due to its environmental friendliness and suitable band gap, Sn-based perovskite solar cells (PSCs) still need to overcome practical stability and efficiency problems. Here, a passivation material tris(hydroxymethyl)aminomethane (THAM) with amino and multihydroxyl groups is added into the formamidinium tin iodide (FASnI3) perovskite to reduce the defect state density and unnecessary nonradiative recombination of the film, which eventually not only improves the light absorption ability and film crystallinity but also inhibits the oxidation of Sn2+. Applications of the THAM-doped FASnI3 perovskite films into PSCs acquire a high power conversion efficiency of 9.18%. Moreover, the storage stabilities of PSCs are obviously prolonged because of the improved Sn-based perovskite film quality, showing excellent stability of 550 h to keep 85% of its initial efficiency (in an N2 environment).