Room-temperature white and color-tunable afterglow by manipulating multi-mode triplet emissions

Herein, we succeed in achieving room-temperature persistent white afterglow by manipulating multi-mode triplet emissions from a single purely organic phosphorescence molecule. Two D-A-A′-D type organic isomers p DCzPyCN and o DCzPyCN are designed and synthesized, with two carbazolyls as the donors and pyridine and a cyanogroup as the acceptors. Amazingly, o DCzPyCN and p DCzPyCN manifest white afterglow and green afterglow at room temperature, which lasts for over 3 s and 2 s, respectively. The white afterglow of o DCzPyCN is made up of thermally activated delayed fluorescence (TADF) (455 nm, ∼90 ms), distinguishable thermally activated delayed phosphorescence (TADP) (483 nm) and organic ultralong phosphorescence (OURTP) from the intermolecular interaction-stabilized triplet state (T 1 *) (542 nm and 592 nm, ∼240 ms). The calculated CIE x , y chromaticity coordinates are (0.30, 0.35) in the white-light zone. The green afterglow of p DCzPyCN contains TADF (475 nm, ∼51 ms), TADP from the lowest molecular triplet state (T 1 ) released from T 1 * (490 nm, ∼55 ms), and weak T 1 * emission (542 nm and 592 nm, ∼46 ms and ∼49 ms). Fascinatingly, both isomers adopt the unique multi-mode triplet emission mechanism but different emission components play a leading role in the final afterglow for each isomer, leading to the different afterglow colors. Single crystal analyses and TD-DFT calculations evidence the T 1 * phosphorescence. Temperature-dependent experiments validate the TADF and TADP of p DCzPyCN and o DCzPyCN. To the best of our knowledge, this is the first time that the afterglow color has been tuned and single component white afterglow has been finally realized by manipulating multi-mode triplet emissions. This work will help gain deep insight into the mechanism for organic afterglow and extend its application scope. Two isomers p DCzPyCN and o DCzPyCN are designed and synthesized. Amazingly, o DCzPyCN manifest white afterglow at room temperature. This is the first time that single-component white afterglow has finally been realized.