Low-dimensional hybrid copper(I) halides single crystals: synthesis, structures, and tunable photoluminescence

[Display omitted] •High-quality novel centimeter-sized [1,2-propylenediamine (PDA)]CuX3 (X=Cl, Br, I) single crystals are cultivated.•[1,2-PDA]CuX3 exhibit tunable photoluminescence light emission from cyan to purple at room temperature.•Photoluminescence mechanism of [1,2-PDA]CuI3 single crystal is studied by temperature-dependent spectroscopy. Low-dimensional organic–inorganic hybrid copper(I) compounds have attracted much attention due to their high luminescence efficiency and non-toxicity. In this study, we synthesized three novel centimeter-scale Cu(I)-based hybrid [1,2-PDA]CuX3 (X=Cl, Br, I) single crystals using the solvent evaporation method. [1,2-PDA]CuCl3 and [1,2-PDA]CuBr3 exhibit zero-dimensional crystal structures composed of separated binary edge-sharing [CuX4]3- (X=Cl, Br) tetrahedra, while [1,2-PDA]CuI3 exhibits a one-dimensional crystal structure composed of chains of corner-sharing [CuI4]3- tetrahedra. The photoluminescence emission of [1,2-PDA]CuX3 (X=I, Cl, Br) ranges from cyan to purple light at room temperature, showing a tunable pattern with the halogen changes. The photoluminescence quantum yield of the [1,2-PDA]CuI3 single crystal was measured to be 33.5 %. Density functional theory calculations demonstrate that all three single crystals have direct bandgaps. The emission mechanisms of [1,2-PDA]CuI3 single crystals were investigated by temperature-dependent photoluminescence spectroscopy, and the broadband emissions were found to be typical of self-trapped exciton emission. It is worth mentioning that the discovery of low toxic, stable, and inexpensive copper(I) compounds paves the way for considering low-cost and environmentally friendly copper halides for practical applications.