Temperature-Dependent Dual Fluorescence and Phosphorescence of Low-Dimensional Hybrid Cadmium Halides

Organic-inorganic hybrid metal halides (OIHMHs) have undergone advanced development due to their exceptional photophysical properties and the increasing demands in optoelectronic applications. It is significant to perform a structural design strategy to realize tunable multicolor luminescence in OIHMHs. In this study, three new cadmium-based OIHMH single crystals─[PzPy]CdCl₄ (PzPy = 3-(2-pyridyl)pyrazole), [APd]₂Cd₂Cl₈·2H₂O (APd = 3-aminopiperidine), and [APrIm]Cd₂Cl₆ (APrIm = N-(3-aminopropyl)-imidazole)─were prepared via a facile saturated crystallization method with adjustable anionic skeletons of 0D [CdCl₄]²⁻ tetrahedron, 1D [Cd₂Cl₈]⁴⁻ chain, and 2D [Cd₂Cl₆]²⁻ layer, respectively. Under UV light excitation, these hybrid cadmium halides exhibit temperature-dependent broadband blue fluorescence and green phosphorescence. Comprehensive spectroscopic investigations suggested that the dual fluorescence and phosphorescence are attributed to singlet- and triplet-state self-trapped excitons (STEs), respectively. Therefore, solid-state light-emitting diodes were realized based on these cadmium-based OIHMHs. In brief, this work offers a new perspective on modifying the structure and luminescent properties of hybrid metal halides, which will promote the rational design of low-dimensional (1D) OIHMHs with excellent luminescence performance in the future.