Micromechanical Chemical Synthesis of Two Tin-Based Organic-Inorganic Hybrid Perovskites for High Color Rendering Index Solid-State Lighting

Abstract

Low-dimensional organo-inorganic hybrid halide perovskites with broadband emission characteristics are crucial for achieving excellent color rendering indices in solid-state lighting devices. Tin-based perovskites are promising lead-free candidates for their narrow band gap, high charge mobility, and low toxicity. However, the susceptibility of Sn2+ to oxidation results in poor stability and strict synthesis conditions, posing a challenge for commercial application. Herein, two tin-based perovskites, [Br(CH2)2NH3]4SnBr6 ((BEA)4SnBr6) and [Br(CH2)3NH3]4SnBr6 ((BPA)4SnBr6), were synthesized using an economical and environmentally friendly micromechanical chemical method under air conditions. Both perovskites exhibit a stable broadband orange-red light emission. Despite similar emission wavelengths (~610 nm) and full width at half maximum (FWHM) (~110 nm), they show a huge difference in lifetimes and photoluminescence quantum yields (PLQYs). (BPA)4SnBr6 has a much longer lifetime (3.12 μs) and higher PLQY (79%) than that of (BEA)4SnBr6 due to its triplet self-trapped excitons (STEs) luminescence mechanism. Both compounds demonstrated good air stability; their photoluminescence intensity recovered to more than one times the initial value after 18 days in the air. Moreover, a stable warm white LED device with a color rendering index of 95.1% was fabricated by coating blue phosphor BaMgAl10O17: Eu2+, green (Sr,Ba)2SiO4: Eu2+, and orange-red BPA4SnBr6 on a commercial 365 nm LED chip. This study provides a novel approach for the rapid synthesis of high-performance tin-based perovskites and the fabrication of white LED devices with superior color rendering indices.

Keywords: Photoluminescence, Micromechanical chemistry, Tin-based perovskites, Color rendering index, Stability