Sulfonyl and Carbonyl Groups in MSTC Effectively Improve the Performance and Stability of Perovskite Solar Cells

Intrinsic defects are key factors that would affect the performance and stability of perovskite solar cells (PSCs). Herein, a sulfonamides additive, methyl 3‐sulfamoyl‐2‐thiophenecarboxylate (MSTC), is introduced into the PbI 2 or FAI/MACl/MABr precursor solution, to prepare high‐quality PSCs with a two‐step method. After the addition of MSTC, all the devices show enhanced performance. With optimized MSTC incorporated into PSCs, the champion power conversion efficiency (PCE) of the PSCs is increased from 19.19% to 22.14%, and the stability is also improved. The MSTC‐FAI based device can still maintain 89% of its initial PCE compared to 68% of the control one after 15 days in ambient condition under relative humidity of 40–50% at room temperature in dark. Test results reveal that amido group in MSTC would coordinate with PbI 2 or FAI through hydrogen bonding (NH···I), thus effectively enhancing the performance of devices. Nevertheless, the sulfonyl and carbonyl groups in MSTC would coordinate with the FAI precursor through chemical bond of COS and COC. And with the hydrogen bonding connection between MSTC and FAI, the inherent defects in the MSTC‐FAI based device are effectively suppressed, leading to the enhanced photovoltaic performance.