Dynamic Phosphorescence/Fluorescence Switching in Hybrid Metal Halides Toward Time-Resolved Multi-Level Anti-Counterfeiting

Hybrid metal halides (HMHs) with time-resolved luminescence behavior promise to be a breakthrough in multi-level anti-counterfeiting, but controlling the dynamic switching between phosphorescence and fluorescence is extremely challenging. Herein, an array of 0D HMHs is constructed by screening the pi-conjugated ligand with room-temperature phosphorescence (RTP). Compared to the organic chromophore, (ETPP)2ZrCl6 possesses a misaligned stacking and rigid structure, contributing to an improved phosphorescence quantum yield (Phi P = 27.50%) and an extended phosphorescence lifetime (tau = 0.6234 s), as the intervening of inorganic unit [ZrCl6]2- suppresses the energy losses caused by nonradiative relaxation and prompts the intersystem crossover (ISC) process. Not only that, the interplay of phosphorescence-fluorescence dual-mode emission can be intelligently controlled by doping the active metal Te4+, resulting in a dynamic switching between RTP phosphorescence and self-trapped exciton (STE) fluorescence. DFT calculations reveal the governing origins of RTP-STE from the intermolecular ISC channels and spin-orbit coupling (SOC) coefficients. These precise images into periodic pixelated arrays enable the multi-level anti-counterfeiting and information encryption. This work proposes a fluorescence-phosphorescence co-modulating strategy under the premise of dissecting the structural origins for optimizing RTP phosphorescence, which paves the way for designing high-security-level anti-counterfeiting materials. (ETPP)2ZrCl6 possesses a misaligned stacking and rigid structure due to the intervention of [ZrCl6]2-, thus contributing to an improved phosphorescence quantum yield (Phi P = 27.50 %) and an extended phosphorescence lifetime (tau = 0.6234 s). Beyond that, the dual-mode emissions are intelligently controlled by doping the active Te4+ with 5s2 lone-pair electron, resulting in the dynamic switching between RTP phosphorescence and STE fluorescence. image