Isomeric Zero-Dimensional Hybrid Copper(I) Iodides as Highly Efficient Multicolor Phosphors

The design and construction of new phosphors with significantly different emission colors are key areas in solid-state lighting technologies. Hybrid copper-(I) iodides are excellent candidates with multicolor luminescence due to their remarkable structural diversity, superior luminescence performance, and highly tunable optical characteristics. Here, we synthesize and characterize a series of new 0D isomeric copper iodides, namely, Cu4I4(3-trifluoromethylpyridine)4. The emission center [Cu4I4] cubane coordinates with a sterically hindered 3-trifluoromethylpyridine ligand to form four 0D isolated copper iodide clusters, which show ligand-configuration-dependent photoluminescence. The four polymorphs emit blue, green, yellow, and pure white-light, respectively, with high photoluminescence quantum yields (PLQYs) in the range of 80-95%. Time-resolved photoluminescence spectra of all compounds show long averaged decay lifetime up to 10 mu s. Density functional theory calculations reveal the electronic structures and the emission characteristics at excited states, illustrating the structure-emission relations. Our results demonstrate that the ligand configurations and orientations have strong impact on the distortion of [Cu4I4] cubane at the excited state, leading to different energy transitions and emission colors. This work provides a new design strategy for multicolor luminescent phosphors and presents the first example of pure white-light emission in a copper-(I) iodide system with a near-unity PLQY.