Universal Surface-Defect Passivant for Perovskite Solar Cells Based on N -Phenylglycine for Improved Photovoltaic Performance and Stability

In this work, we use $\mathrm{N}$-phenylglycine (NPG) molecules as a universal passivant for all typical surface defects of perovskite to improve the photovoltaic performance and stability of perovskite. Our results show that NPG molecules can passivate the organic cation vacancy, $\mathrm{I}$ vacancy, $\mathrm{Pb}$ vacancy, and $\mathrm{Pb}$-$\mathrm{I}$ antisite surface defects of perovskite, through either coordinate and/or hydrogen bonding, or the van der Waals interaction. More interestingly, after the $\mathrm{Pb}$ vacancy on the perovskite surface is passivated by NPG, a transition from metallic to semiconducting properties occurs. The perovskite solar cells (PSCs) passivated by NPG have a high power conversion efficiency (PCE) of 21.16% and retain 91% of the initial efficiency after 700 h in humid air, compared with PSCs without passivation (PCE of 18.29% and maintained efficiency of 75%). Our study proposes one general surface-defect passivant for PSCs that significantly boosts photovoltaic performance and stability.