Color-Stable Two-Dimensional Tin-Based Perovskite Light-Emitting Diodes: Passivation Effects of Diphenylphosphine Oxide Derivatives

The performance of tin (Sn)-based perovskite light-emitting diodes (PeLEDs) lags behind their lead analogs due to the challenges of Sn²⁺ oxidation, defect passivation, and fast crystallization. Herein, the passivation effects of diphenylphosphine oxide (DPPO) derivatives on the fabrication of PEA₂SnI₄ films are investigated. The DPPO derivatives with hydroxyl group, or including substituent group with the potential to form hydroxyl group, are unfavorable passivators due to their positive effects in accelerating Sn²⁺ oxidation. In comparison, amino-functionalized DPPO molecule is an effective additive to enhance the photoluminescence of PEA₂SnI₄ films due to the effective defect passivation as well as crystallinity improvement. Based on the optimized films, color-stable pure-red PeLEDs are demonstrated with a full width at half maximum of 23 nm at 630 nm, a maximum luminance of 451 cd m⁻², a maximum external quantum efficiency of 3.51%, and a half-lifetime of 13.7 min at 102 cd m⁻². This work opens new prospects on the selection of effective molecular additives for Sn-based perovskites.