Stabilizing perovskite precursors with the reductive natural amino acid for printable mesoscopic perovskite solar cells

Solution processability significantly advances the development of highly-efficient perovskite solar cells. However, the precursor solution tends to undergo irreversible degradation reactions, impairing the device performance and reproducibility. Here, we utilize a reductive natural amino acid, Nacetylcysteine (NALC), to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells. We find that I2 can be generated in the aged solution containing methylammonium iodide (MAI) in an inert atmosphere and speed up the MA-FA+ (formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase. NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I2 back to I- and provides H+. The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor. Furthermore, NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects. (c) 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press All rights reserved.