Employment of l-Citrulline as an Effective Molecular Bridge for Regulating the Buried Interface of Perovskite Solar Cells to Achieve High Efficiency and Good Stability.

Suppressing the defects from SnO 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) and urea (─NH─CO─NH) groups, during SnO colloidal dispersion to function as a molecular bridge to modulate the SnO/perovskite buried interface. The amino acid group can effectively coordinate with Sn to passivate the oxygen vacancy defects of SnO, and the urea group can interact with uncoordinated Pb and I. These interactions not only improve the electron mobility of SnO but also facilitate the formation of larger grain-size perovskite film. In addition, they can also inhibit the generation of excess PbI 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) 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) could achieve a PCE of 22.70%, which is among the highest PCE reported so far.