Organic–Inorganic Copper Halide Compound with a Near-Unity Emission: Large-Scale Synthesis and Diverse Light-Emitting Applications

Low-dimensional organic–inorganic metal halides (OIMHs) have emerged as promising light emitters due to their broadband emission originating from self-trapped excitons (STE), especially for Cu-based OIMHs. Herein, Cu(I)-based OIMH with a structure of (TPP)₂Cu₄I₆·2DMSO (TPP stays for tetraphenylphosphonium, and DMSO – for dimethyl sulfoxide) has been synthesized, both in form of single crystals and as a microcrystalline powder. This compound exhibits a broadband green emission with a peak at 515 nm and a full width at half-maximum of 78 nm, and a near-unity photoluminescence quantum yield of 99.5%. Experimental data supported by theoretical calculations indicate that the STE emission is responsible for the green emission with a long lifetime of 2.53 µs. Down-conversion light-emitting device with a high luminous efficiency of 50 lm W⁻¹ based on this compound have been fabricated, and white light has also been achieved with a high color rendering index of 96.7. Moreover, green emissive (TPP)₂Cu₄I₆·2DMSO is utilized in scintillators for X-ray detection and imaging, and as a luminescent ink for encryption applications.