Mn-doped 2D Sn-based perovskites with energy transfer from self-trapped excitons to dopants for warm white light-emitting diodes

Abstract

Mn-doped 2D perovskite powders are promising phosphors for warm white light-emitting diodes (LEDs). However, it remains a challenge to solve the problem of lead toxicity and improve the photoluminescence quantum yields (PLQYs). Here, we have successfully prepared Mn-doped 2D Sn-based perovskite materials ((C₈H₁₇NH₂)₂Sn_1−xMn_xBr₄). The PLQYs of (C₈H₁₇NH₂)₂Sn_1−xMn_xBr₄ (x = 0.26) powders reach up to 42%. The as-prepared (C₈H₁₇NH₂)₂Sn_1−xMn_xBr₄ exhibits a single broad photoluminescence (PL) band, differing from the dual peaks of Mn-doped lead halide perovskite quantum dots. Theoretical conclusions and experimental results show the competitive relationship between self-trapped exciton (STE) emission from the host crystal and dopant Mn d–d transition emission. With increasing Mn dopant concentration, the PL spectra exhibit red shifts and the full width at half-maximum (FWHM) becomes larger, which is constructive for warm white LEDs. The fabricated warm white LEDs based on (C₈H₁₇NH₂)₂Sn_1−xMn_xBr₄ show a warm white light correlated color temperature (CCT; 3542 K) and a high color-rendering index (R_a, 88.12). Our work provides new possibilities for optoelectronic devices based on lead-free perovskite materials.