Organic‐Inorganic Cuprous Halides With Reversible Photoluminescence for Multiple Optical Applications

Abstract 0D organic‐inorganic Cu(I)‐based halides have gained significant attention due to their low toxicity, structural adjustability, and moderate fabrication conditions. However, it is still challenging to explore stable and efficient 0D hybrid Cu(I)‐based halides that have phase transition and tunable spectra for multifunctional photoelectric applications. Herein, two 0D copper halides, green‐emissive (MTPP) 2 CuI 3 and yellow‐emissive (MTPP) 2 Cu 4 I 6 (MTPP = Methyltriphenylphosphonium), are successfully synthesized using a slow cooling method. Both compounds exhibit high photoluminescence quantum yield (PLQY) of 81.95 and 99.7%, and remarkable steady‐state light yield of 38 750 and 63 700 photons per MeV, respectively. The scintillation screen of the two compounds based on vacuum‐filtration enables high X‐ray imaging resolution of 17.83 and 18.49 lp mm −1 , showing great potential in practical X‐ray imaging applications. Moreover, a reversible and fast phase transformation between them occurs when stimulated by ethanol or MTPP solutions, without requiring additional thermal treatment, which endows them with a high level of anti‐counterfeiting under room temperature (RT). It is worth noting that they display remarkable resistance to water, maintaining its phase purity even after being immersed in water for 30 days. This study introduces a new approach to investigate the 0D Cu‐based halides that exhibit excellent scintillation performance, stability, and efficient photoluminescence tunability for multiple applications.