Lead-Free Tin-Based Perovskite LEDs Toward Rec. 2020: Organic Anion Coordination for Oxidation Suppression

Lead halide perovskites are highly promising for optoelectronic applications, but the toxicity of lead (Pb) ions presents significant health and environmental challenges. Recent efforts to replace Pb metal with tin (Sn) face challenges due to Sn's oxidation instability, limiting its use in perovskite light-emitting diodes (PeLEDs). While Sn metal additives are traditionally utilized to mitigate the oxidation of Sn²⁺, alternative stabilization strategies remain unexplored. In this study, an organic anion-coordination for oxidation suppression (OCOS) strategy is introduced, which effectively stabilizes Sn-based perovskites. By incorporating alkali metal-organic anions, OCOS significantly enhances external quantum efficiency (EQE) and luminance. The organic anions coordinate with Sn²⁺ via lone pair electron interactions, while alkali metals inhibit Sn vacancy formation, further enhancing film quality and device performance. Moreover, the energetic stabilization induced by the OCOS strategy is quantified by density functional theory (DFT) calculations and clarify its mechanism in terms of electronic structural change. Using this strategy, an EQE of 10.01% is achieved at an emission wavelength of 638 nm in lead-free Sn-based PeLEDs. This work provides new insights into Sn stabilization strategies and advances the development of lead-free perovskite optoelectronic devices.