Alkylamine screening and zinc doping of highly luminescent 2D tin-halide perovskites for LED lighting

Abstract

In recent years, two-dimensional (2D) layered tin halide perovskites have attracted much attention due to their excellent luminescence properties compared with their three-dimensional (3D) analogs. Here, we synthesized 2D perovskites of the form (RNH₃)₂SnBr₄ through a facile hot-injection approach without the use of toxic tri-n-octylphosphine (TOP) as the solvent. We found that these compounds have strong photoluminescence (PL) emission with high PL quantum yields (QY) of 35% ((C₆H₁₃NH₃)₂SnBr₄), 82% ((C₈H₁₇NH₃)₂SnBr₄), 60% ((C₁₂H₂₅NH₃)₂SnBr₄) and 50% ((C₁₈H₃₅NH₃)₂SnBr₄). Among them, ((C₆H₁₃NH₃)₂SnBr₄) was synthesized for the first time; however, (C₁₈H₃₆NH₃)₂SnBr₄ perovskites showed the best stability with a PL QY decrease of less than 1% after 30 days under ambient air and humidity conditions. In addition, other 2D (C₈H₁₇NH₃)₂SnX₄ (X = Br, I, or mixture) perovskites were prepared by adjusting the halide ratio, resulting in spectral tunability from yellow to red. Interestingly, through Zn²⁺ doping, the morphology became more uniform, and the PL stability was significantly improved. Finally, we used Zn²⁺-doped (C₈H₁₇NH₃)₂SnBr₄ yellow phosphor to fabricate UV-pumped yellow LEDs. We expect these 2D perovskites to be promising phosphors in future solid-state lighting and display technologies.