Dual Interfacial\nModifications by a Natural Organic\nAcid Enable High-Performance Perovskite Solar Cells with Lead Shielding

Effective interfacial modification of the perovskite\nlayer is a\nfeasible approach to improve the efficiency and stability of perovskite\nsolar cells (PSCs). Herein, we introduce a dual interfacial modification\napproach utilizing a natural organic acid, citric acid (CA), to enhance\nboth interfaces adjacent to the crucial perovskite layer within the\nPSC structure. First, a CA thin layer is deposited on the top of a\nSnO<sub>2</sub> electron transport layer to mitigate the corrosive\neffects of alkaline impurities in SnO<sub>2</sub> on the perovskite\nfilm and to control the crystal growth of the perovskite. Then, the\nperovskite film is post-treated with CA to adjust the surface condition\nand passivate the defects on the film surface; thus, the interface\ncontact around perovskite is strengthened, thereby facilitating charge\ntransfer at the interfaces. Besides, CA also provides an in situ suppression\nof lead leakage in case the perovskite film is destroyed, owing to\nthe strong chelating interactions of carboxyl groups with Pb<sup>2+</sup>. The photovoltaic performance and stability of the final PSCs are\nsignificantly enhanced, with the power conversion efficiency (PCE)\nincreasing from 21.02 to 24.20%. This optimization of the important\ninterfaces adjacent to the perovskite layer through surface treatment\nwith a natural organic acid offers a practical method for enhancing\nthe performance and stability of environmentally friendly PSCs.