Natural Antioxidant‐Inspired Interfacial Engineering for Stable and High‐Performance Perovskite Solar Cells

ABSTRACT Although perovskite solar cells (PSCs) have recently achieved high certified power conversion efficiencies ( PCEs ), operational instability remains a critical obstacle to commercialization. In particular, superoxide (O 2 ∙ − ) generated at metal‐oxide charge‐transport layers rapidly decomposes perovskites by deprotonating the organic cations (FA⁺ and MA + ) and therefore must be suppressed. Nevertheless, under operating illumination, the formation and diffusion of O 2 ∙ − are unavoidable as long as metal oxides are employed in PSCs. To address this, we introduce the natural antioxidant taurine at the SnO 2 /FAPbI 3 interface to suppress O 2 ∙ − diffusion via chemical radical quenching. We elucidate the taurine‐mediated O 2 ∙ − quenching mechanism through density functional theory (DFT) calculations supported by experiments. In addition, we find that I 2 is concomitantly reduced to I‐ during the quenching process. This antioxidant interface prevents O 2 ∙ − induced perovskite decomposition under strongly oxidizing conditions. Moreover, the multifunctional groups of taurine form a chemical bridge between SnO 2 and FAPbI 3 , reducing interfacial defect density, enhancing carrier mobility, and suppressing non‐radiative recombination. Consequently, the taurine‐buried interface enables an improved PCE with increased open‐circuit voltage ( V OC ) and fill factor ( FF ), while markedly enhancing the light‐soaking and operational stability of PSCs.