Highly efficient copper-based halide single crystals with violet emission for visible light communication

K2CuBr3 single crystals (SCs) are synthesized using a cooling-induced crystallization method with violet emission due to self-trapped excitons (STEs) under photoexcitation. The prepared K2CuBr3 SCs exhibit a high photoluminescence quantum yield (PLQY, 79.2%) and excellent stability against moisture, heat and UV light. When the K2CuBr3 SCs are used as a light source for visible light communication the data transmission rate reaches a striking 248 Mbps, which is more than 33-fold the -3 dB bandwidth.