Dual Blue Fluorescence and Green Phosphorescence of Hybrid Cadmium Halide for Anti-counterfeiting

Abstract

Zero-dimensional (0D) metal halides-based room-temperature phosphorescence (RTP) materials have received extensive attention with wide application prospects, but remains to suffer from low phosphorescence efficiency, which restricts their progress in cutting-edge photonic applications. In this work, a new zero-dimensional (0D) cadmium halide [BTPP]2CdBr4 (BTPP = benzyl triphenylphosphonium bromide) has been successfully synthesized through room-temperature solution method. Under excitation of 357 nm and 309 nm UV light, [BTPP]2CdBr4 displays dual blue fluorescence and green phosphorescence with lifetimes of 1.38 ns and 76.18 ms, respectively. The quantum yield of phosphorescence reaches up to be 43.68%, which exceeds most of the 0D metal halide-based RTP materials. Detailed experimental characterizations and theoretical calculations demonstrate that the fluorescence and phosphorescence originate from the radiative recombination of singlet self-trapped excitons (STEs) and triplet π-π* charge transfer in [BTPP]+ cation, respectively. Benefitting from the dual luminescence, [BTPP]2CdBr4 can be explored as dual space- and time-resolved luminescent label with applications in anti-counterfeiting and information security, etc. This work provides a fundamental structural engineering strategy to design highly efficient 0D metal halides-based RTP materials.