Effect of the organic molecules on the luminescence properties of Cd-based organic-inorganic hybrid compounds

Recent researches on organic-inorganic hybrid materials revealed the pertinent emissive properties of Cd-based compounds. Illogically, the role of the organic sub-lattice in the optical behaviors of hybrid materials had been neglected by several researchers. In this work, we studying the effect of the substitution of the organic molecule on the photoluminescence properties of three new zero-dimensional compounds (C₆H₁₀(NH₃)₂)CdBr₄∙H₂O (CdDACH), (C₅H₆N₂Cl)₂CdBr₄∙H₂O (CdACP), and (C₁₂H₁₃N₂O)₂CdBr₄ (CdODA). The structural characterizations revealed that the inorganic framework is constituted by isolated tetrahedra CdBr₄ and the organic part is formed by protonated ammonium salt. The UV-Vis absorption spectra analysis showed that the three compounds exhibit an intense absorption peak in the UV region and no characteristic absorption is observed in the visible region. These materials are characterized with large direct band-gap energies above 4 eV. The solid-state photoluminescence measurements showed that the CdDACH exhibits a broad green-blue emission resulting from the self-trapped excitons (STE) within the inorganic tetrahedra. The substitution of the organic molecule C₆H₁₀(NH₃)₂ by the π-conjugated aromatic ones, C₁₂H₁₃N₂O and C₅H₆N₂Cl, yielded a white-light emission with extra-high color rendering index (CRI) above 90 with chromaticity coordinates (x,y) and correlated color temperatures (CCT) comparable to those of the pure day-light. (author)