Industrial mass production of novel mixed-halide Cs3Cu2Cl5-xIx and Cs5Cu3Cl8-xIx compounds with greatly enhanced stability and luminescent efficiency by compositional engineering

Copper(I) halides have recently attracted increasing attention in a variety of photonics applications, owing to their highly luminescent efficiency, nontoxicity, and low-dimensional electronic structure. Moreover, combining compositional engineering and mass production of new materials may further enrich the research and application of functional materials. Herein, we controllably synthesized two series of novel mixed-halide Cs3Cu2Cl5-xIx and Cs5Cu3Cl8-xIx powders via the compositional engineering for the first time. The crystal structures are identified with Rietveld refinement and density functional theory calculations. The mixed-halide compound exhibits relatively wide full width of half-maximum (~70 nm), adjustable bandgap (from 449 nm to 486 nm), larger Stokes shifts (~200 nm), and dramatic improved stability with high efficiency (photoluminescence quantum yield at least 90.61%), which present a scalable strategy for mass production for practical applications. In addition, the controllable phase transformation from blue-emitting Cs3Cu2I5 to yellow-emitting CsCu2I3 was confirmed. Most notably, the white light is obtained by combining novel Cs3Cu2Cl5-xIx/Cs5Cu3Cl8-xIx with yellow-emitting CsCu2I3 powders. Based on this, we firstly introduce the blue-emitting Cs5Cu3Cl7I powders in white LED fabrication by combining ultraviolet chip and as-prepared yellow-emitting CsCu2I3 powders, to generate high-quality and stability white light with CIE coordinates of (0.335, 0.398) and colour rendering index value of 77.8. For comparison, red-emitting CaAlSiN3:Eu2+ phosphors are also introduced for LED package to substitute CsCu2I3 powders, which exhibit the high colour rendering index of 89.2. This work not only develops new mixed-halide compounds with high stability and performance, but also provides the unique strategy for promoting industrialization process of LED backlights.