Tunable Blue-Light-Emitting\nOrganic–Inorganic\nZinc Halides with Thermally Activated Delayed Fluorescence and Room-Temperature\nPhosphorescence

Hybrid metal halides have received great interests in\nthe field\nof solid-state lighting technologies due to their diverse structures\nand excellent emission properties. In this work, we report the synthesis\nand characterization of four blue-emitting zero-dimensional hybrid\nmetal halides, namely, (2HP)<sub>2</sub>ZnCl<sub>2</sub>, (2HP)<sub>2</sub>ZnBr<sub>2</sub>, (2TP)<sub>2</sub>ZnCl<sub>2</sub>, and (2TP)<sub>2</sub>ZnBr<sub>2</sub> (2HP = 2-hydroxypyridine, 2TP = pyridine-2-thiol).\nBy changing the ligands and halides, a remarkable increase in the\nphotoluminescence quantum yield of (2HP)<sub>2</sub>ZnCl<sub>2</sub> (44.7%) compared to (2TP)<sub>2</sub>ZnBr<sub>2</sub> (1.8%) is\nrealized. The 2HP series features excitation-dependent emission characteristics,\nwhereas the 2TP series does not due to the effect of a different organic\nligand. Utilizing time-resolved and temperature-dependent photoluminescence\nspectroscopies, all four compounds exhibit both thermally activated\ndelayed fluorescence and room-temperature phosphorescence properties.\nThese materials have excellent ambient and thermal stabilities and\nare solution-processable. Our work shows the importance of carefully\nincorporating organic ligands with the appropriate inorganic metal\ncenter to achieve tunable emission properties.