Ultralong afterglow enabled by energy relay from room-temperature phosphorescent matrixes to local dipoles

Long-persistent afterglows based on organic donor-acceptor systems feature ultra-long duration reaching hours, leading to the advantages in long-time-range display and bio/medical applications. However, the understanding of this optical phenomenon is insufficient. Herein, dibenzothiophene-phosphine oxide hybrids named nDBTxPO with different room temperature phosphorescence characteristics are used as acceptor matrixes. It shows that after doping N,N,N′,N′-tetramethylbenzidine (TMB) as donor, afterglow intensities and durations of nDBTxPO:1% TMB are strongly correlated to the stabilized triplet state (Tn*) properties of nDBTxPO. Compared to other congeners, high-population and high-lying Tn* state of 28DBTDPO matrix supports the positive and efficient energy transfer to nCT* states of 28DBTDPO-TMB local dipoles in the doped film. This energy relay between two long-persistent Tn* and nCT* states is the key determinant resulting in the longest afterglow of 28DBTDPO:1% TMB. This work provides clear insight into energy transfer for lightly-doping donor-acceptor systems, therefore will promote the accurate system design for practical applications. Long-persistent afterglow can be achieved in organic materials, but understanding of the processes is limited. Here, the authors report the study of acceptor matrices with dopants for insight into energy transfer processes.