Localized Charge‐Transfer State Antennas in Light‐Harvesting Microcrystals for Efficient Room‐Temperature Phosphorescence

Abstract The charge‐transfer (CT) complexes with significant electron delocalization demonstrate abundant appealing physicochemical features and unique orbital hybridization, creating great promise as artificial light‐harvesting antennas for advanced optoelectronics, such as high‐performance organic room‐temperature phosphorescence (RTP). Herein, originally, a localized CT complex is proposed in organic microcrystals for exceptional orange‐emissive RTP with photoluminescence peaks at 575 and 625 nm based on the light‐harvesting antennas of CT states in organic microcrystals with donor doping. The localized CT state antennas can capture more singlet excitons, and transition them into triplet excitons, efficiently promoting intersystem crossing (ISC). Owing to the dense packing structure and strong CT interaction, the generation and stabilization of triplet excitons under ambient conditions are facilitated, imparting effective RTP with a lasting afterglow of up to 3 s. The controlled intensity ratio of fluorescence and phosphorescence is successfully achieved via finely adjusting the donor doping ratio, presenting a tunable CIE evolution from (0.42, 0.30) to (0.25, 0.12). The potential applications of these light‐harvesting microcrystals in information encryption and flexographic printing are illustrated.