Adjusting the Crystallization of Tin Perovskites through Thiophene Additives for Improved Photovoltaic Stability

Tin-based perovskites (Sn-PVK) are promising lead-free alternatives for efficient photovoltaic technology, but they face challenges related to bulk and surface defects due to suboptimal crystallization and Sn2+ oxidation. Introducing thiophene-2-ethylammonium halides (TEAX, where X = I, Br, Cl) improves FASnI3 crystallization and reduces Sn4+ formation. This is achieved by adjusting the crystallization dynamics through the formation of a complex between S and Sn during the preparation of the precursor solution, which also inhibits Sn2+ oxidation in the resulting films. In solar cells, these additives boost power conversion efficiency (PCE) from 6.6% (without additives) to 9.4% (using TEABr), with further enhancement to 12% by adjusting selective contacts. The addition of TEAX also increases the Sn2+ content, outperforming control. Devices with TEABr maintained over 95% of their initial PCE after 2000 h in N2 under continuous operation with 1 sun simulated illumination.