Employment of <scp>l</scp> ‐Citrulline as an Effective Molecular Bridge for Regulating the Buried Interface of Perovskite Solar Cells to Achieve High Efficiency and Good Stability

Abstract Suppressing the defects from SnO 2 and perovskite interface is essential for the fabrication of large‐area n–i–p perovskite solar cells (PSCs) with the needed lifetime and efficiency for commercialization. Here, we report the employment of l ‐citrulline (CIT), which has amino acid (─COOH, ─NH 2 ) and urea (─NH─CO─NH 2 ) groups, during SnO 2 colloidal dispersion to function as a molecular bridge to modulate the SnO 2 /perovskite buried interface. The amino acid group can effectively coordinate with Sn 4+ to passivate the oxygen vacancy defects of SnO 2 , and the urea group can interact with uncoordinated Pb 2+ and I − . These interactions not only improve the electron mobility of SnO 2 but also facilitate the formation of larger grain‐size perovskite film. In addition, they can also inhibit the generation of excess PbI 2 and the nonphotoactive δ phase to result in suppressed trap‐assisted nonradiative recombination. Consequently, the incorporation of CIT helps achieve a champion power conversion efficiency (PCE) of 25.95% (0.07065 cm 2 ) in PSC with improved shelf life/light soaking stability. When combined with an antisolvent‐free slot‐die coating technique in air, the solar modules (23.26 cm 2 ) could achieve a PCE of 22.70%, which is among the highest PCE reported so far.