Low-Temperature Solution Synthesis of Stable Cs₃Cu₂Br₅ Single Crystals for Visible Light Communications

Inorganic perovskites CsPbX₃ (X = Cl, Br, I) have shown great potential as luminescent materials for a wide range of photoelectric devices. However, the practical use of these materials is limited due to the toxicity of lead and poor stability. Here, we present a facile low-temperature, solution-based method to synthesize lead-free and highly stable Cs₃Cu₂Br₅ single crystals (SCs) without the use of organic solvents. Owing to the self-trapped exciton emissions, Cs₃Cu₂Br₅ SCs exhibit a strong broadband blue emission with a high photoluminescence quantum yield (PLQY) upon 254 nm ultraviolet light excitation. In addition, the Cs₃Cu₂Br₅ SCs show a high stability against heat, humidity, and UV light. Therefore, the Cs₃Cu₂Br₅ SCs are utilized as emitters in white light emitting diodes (WLEDs), demonstrating a high color rendering index of 81 and a decent commission internationale de l'Eclairage coordinate of (0.30, 0.34). Furthermore, the prepared WLEDs are used in wireless visible light communications, showing a -3 dB bandwidth of 6.7 MHz and an achievable data rate of 45 Mbps. Our study provides a novel organic-solvent-free, low-temperature method to synthesize Cs₃Cu₂Br₅ SCs and could promote the development of Cu-based metal halides in visible light communications.