Stable cyan and white light-emitting diodes enabled by branched cations sterically stabilized 2D/3D perovskites

Abstract As an indispensable part of the visible light region, cyan emission (470 nm–500 nm) is of great importance in lighting, displays, and light communication. Metal halide perovskite materials have made significant progress in the field of luminescent materials and devices. However, the corresponding cyan emission through halide mixing is non-stable due to halogen migration and phase separation. Herein, we developed a steric stabilization approach to tune and stabilize the cyan emission of methylammonium (MA)-based perovskites. Dimethylammonium (DMA+) lead bromide, with the small DMA+ branched cation, was used as intermediate to react with MABr, forming blue-to-green emissive (MA)x(DMA)PbBr3+x compounds simular to the low-dimensional perovskites. Furthermore, protonated (trimethylsilyl)methylamine (TmMA), the larger branched cation, was adopted as an interlayer space to further reduce the perovskite dimension, tuning the emission to the cyan region. The combination of the two branched cations enabled us to achieve a champion photoluminescence quantum yield (PLQY) of ~87.8% (peak wavelength ~486 nm). Moreover, the as-synthesized double cations modified perovskites in combination with  LED InGaN chip can be used to fabricate stable cyan emission LEDs with improved durability (over 1000 min) and white LEDs with increased color rendering index (from ~73.1 to ~81.7).