Simple cuprous iodide complex‐based crystals with deep blue emission and high photoluminescence quantum yield up to 100%

Luminescent cuprous complexes have attracted much attention due to their low cost, rich photophysical properties, and hence extensive applications in various fields. In this work, we report the synthesis, structure and photophysical properties of a simple and highly efficient deep blue emission cuprous iodide complex, namely CuI (PPh 3 ) 2 ( t ‐BuPy), where PPh 3 and t ‐BuPy stand for triphenylphosphine and 4‐tert‐butylpyridine, respectively. The complex was synthesized with a one‐pot method, and showed a super high photoluminescence quantum yield up to 100% and a maximum emission wavelength at 454 nm in crystals at room temperature. Based on density functional theory calculation, the emission likely comes from iodide to 4‐tert‐butylpyridine charge transfer and some copper to 4‐tert‐butylpyridine charge transfer excited states. Two reference complexes, CuI (PPh 3 ) 2 (IQu) (IQu = isoquinoline) and Cu 2 I 2 (PPh 3 ) 2 ( t ‐BuPy) 2 , were also synthesized, and the photophysical properties of the three compounds in various forms such as crystalline powder, thin film and solution at both room temperature and 77 K were studied for comparison. These results give clues on how the N‐heteroaromatic ligand (4‐tert‐butylpyridine vs. isoquinoline), coordinating style (mononuclear vs. binuclear), sample form (crystalline powder vs. thin film vs. solution) and temperature (room temperature vs. 77 K) affect the photophysical properties of luminescent cuprous iodide complex.