Recent progress in triplet energy transfer systems toward organic afterglow materials.

Organic room-temperature phosphorescence (RTP) has shown potential applications in the fields of biomedical imaging, chemical sensing, anti-counterfeiting, and encryption. Inspired by natural photosynthesis, artificial light-harvesting systems based on the phosphorescence-type energy transfer (ET) from the triplet excited states of organic RTP emitters have emerged as promising candidates to expand organic afterglow materials and promote practical applications. This review presents a fundamental understanding of phosphorescence-type ET processes, including the one-step triplet-to-singlet ET, stepwise triplet-to-singlet-to-singlet ET, and triplet-to-triplet ET. We highlight significant advances in the design, modulation, and application of phosphorescence-type ET systems and provide an outlook on application prospects and challenges.