Highly symmetric Lewis base coordinated with Sn2+ for reducing voltage loss and retarding oxidation in tin-halide perovskite solar cells

Abstract

The power conversion efficiency (PCE) of tin perovskite solar cells (TPSCs) has made significant breakthroughs recently, making them the most promising eco-friendly perovskite solar cells. However, the uncontrollable crystallization process and the easy oxidation of Sn2+ limit the achievable open-circuit voltage (Voc) and PCE. Herein, a highly symmetric Lewis base small molecule of melamine was introduced into perovskite precursor solution to coordinate with Sn2+, thus effectively modulate the crystallization process of tin perovskite and the oxidation degree of Sn2+. Meanwhile, the introduction of melamine greatly reduced the defect-induced non-radiative recombination in tin perovskites. As a result, the target TPSCs achieved a PCE of 10.3 % and excellent stability, which maintained 85 % of its initial PCE after aging in N2 glove box for 1300 h and 78 % in air for 30 h. Thus, our work provides a feasible strategy to modulate the crystallization process of tin perovskite for reducing the Voc loss in TPSCs.