Metal Halide Single Crystals RbCdCl₃:Sn²⁺ and Rb₃SnCl₇ with Blue and White Emission Obtained via a Hydrothermal...

Until now, effective blue light-emitting materials are essentially needed for the creation of white light and precise color renderings in real-world applications, but the efficiency of blue light-emitting materials has lagged far behind. Here, we present a hydrothermal method to synthesize tin-based metal halide single crystals (RbCdCl₃:Sn²⁺ and Rb₃SnCl₇). Two single crystal materials with different shapes and phases can simultaneously be synthesized in the same stoichiometric ratio. Rb₃SnCl₇ has a bulk shape, while RbCdCl₃:Sn²⁺ has a needle shape. The deep blue emission (436 nm) of RbCdCl₃:Sn²⁺ can be obtained under the optimal excitation wavelength irradiation. However, pure blue emission (460 nm) to white light can be obtained by changing the excitation wavelength in Rb₃SnCl₇. The refinement spectra of the electronic structures of RbCdCl₃:Sn²⁺ and Rb₃SnCl₇ are investigated by density functional theory. It is concluded that the difference in the distribution of Cl energy states leads to the existence of Cl local defect states, which is the reason for the rich luminescence of the two single crystals. These findings provide a path for realizing single-phase broadband white-emitting materials.