Owing to their excellent photoelectric properties, perovskite materials have broad application prospects; however, the toxicity of Pb limits the application of Pb‐based perovskite materials. To overcome this problem, Pb‐free perovskite materials are prepared by replacing Pb with nontoxic elements including Ge and Sn; nevertheless, the stabilities of these materials are low. Herein, single crystals of nontoxic Cu(I)‐based ternary metal halide (Cs3Cu2Br5) with outstanding stabilities and self‐trapped excition (STE) emission are constructed by an antisolvent method for the first time; these crystals exhibit central blue emission at 458 nm and large Stokes shifts. Photoluminescence (PL) intensities of the single crystals remain above 96.9% of their initial intensities when these crystals are exposed to an atmospheric environment for 90 days. Moreover, the stabilities of the Cs3Cu2Br5 single crystals are investigated by temperature‐dependent PL spectroscopy, which suggests a considerable exciton binding energy of 503 meV, and derivative thermogravimetric analysis, which indicate that the temperature of complete decomposition of Cs3Cu2Br5 is above 930 °C. Furthermore, a new class of white light‐emitting diodes with an ultrahigh color rendering index of 97.8 and satisfactory performance is produced using the Cs3Cu2Br5 single crystals. The study demonstrates significant potentials of Cu(I)‐based single crystals in the field of optoelectronics.

The zero‐dimensional perovskite‐like derivative Cs3Cu2X5 (X = Cl, Br, I) with self‐trapped excitons (STEs) photoluminescence (PL) has attracted tremendous interest in the field of optoelectronics. Nonetheless, it is challenging for Cs3Cu2Br5 material to attain full visible spectrum emission and prevent light‐induced photochemical damage to the retina (blue light hazard) in applications. Herein, Mn2+ is chosen as the dopant to alloy into Cs3Cu2X5 via a one‐step solid state synthesis method. Significantly, the series of Mn2+‐doped show the emission peak of 460 nm STEs and the emission peak of 550 nm Mn2+. More importantly, the high energy absorption of Mn2+ facilitates the transfer of exciton energy, contributing to a reduction in blue emission peak at 460 nm. Simultaneously, ≈17.5% of Mn2+ is alloyed into the Cs3Cu2X5lattice to induce the energy transfer channels from the Cs3Cu2X5 host to the Mn2+ guest to lead to the emission of Mn2+, which broadens emission spectrum (400–620 nm) and realizes 80% reduction of the blue emission peak at 460 nm. Additionally, a white light‐emitting diodes can decrease the blue emission band via 71.45% and an ultrahigh color rendering index (CRI) of 94.5 is produced using the 17.5% Mn2+: Cs3Cu2X5 perovskite‐like derivative powder material.

Due to its excellent optical properties, perovskite materials have a wide range of application prospects in the field of optoelectronics. Nevertheless, traditional Pb-based perovskite quantum dots (QDs), especially blue-emission quantum dots, have attracted more attention because of their poor stability. Moreover, the poorly passivated quantum dots surfaces is highly susceptible by the external environment, so finding suitable surface ligands not only enhances the photoluminescence (PL) performance but also improves the optical stability. In this work, mixed-halide blue CsPbBr 1.5 Cl 1.5 perovskite quantum dots are synthesized rapidly by the hot-injection method. The SCN − (thiocyanate) also modifies the surface of QDs to enhance PL intensity. Then, the short-chain ligand thiol can be exchanged with the traditional long-chain ligand for improving stability. After a series of surface treatments, the morphology of the quantum dots always maintains the cubic phase and the fluorescence intensity increases by 34.8%. The photostability of the experimental sample is improved.