Zero-dimensional cadmium-based metal halide with near-unity photoluminescence quantum efficiency

Abstract

Zero-dimensional (0D) organic–inorganic metal halides have recently gained increasing attention due to their unusual structure and exceptional photoelectric properties. As a feasible strategy, the introduction of dopants is useful for modifying the optical properties of the host material. Here, a class of 0D (C₈H₁₄N₂)₂CdCl₆ single crystals were used as the host, and their optical properties were significantly improved by Sb³⁺ and Mn²⁺ doping. Sb³⁺ ions were introduced as new self-trapped centers, achieving bright yellow emission (556 nm) with a high photoluminescence quantum yield (PLQY) of 91.42% and a correlated color temperature of 3820 K. Unlike the self-trapped exciton (STE) emission introduced by Sb³⁺ doping, the ion luminescence achieved by Mn²⁺ doping shows excellent red light emission at 634 nm with a PLQY of 95.17%, which is due to the ⁴T₁-⁶A₁ d–d transition. To the best of our knowledge, this is the highest PLQY among Cd-based metal halides. Spectroscopic characterization and first-principles calculations indicate that the broadband emissions originate from the STE emission centers of the [SbCl₆]³⁻ octahedron and the ion emission centers of the [MnCl₆]⁴⁻ octahedron. Interestingly, the two dopants can simultaneously stabilize in the lattice by codoping and show efficient double emission. Furthermore, variable double emission spectra can be achieved by simply tuning the excitation, which endows the material with great flexibility in its optical properties. We prove that the optical characteristics of host materials can be improved and controlled by single and codoping, providing a new paradigm for functional material design emerging from the ideal host–guest combination.