We report ahighly efficient dopant-matrix afterglow system enabled by TADF mechanism to realizea fterglow quantum yields of 60-70 %, which features am oderate rate constant for reverse intersystem crossing (k RISC )t os imultaneously improve afterglow quantum yields and maintain afterglow emission lifetime.D ifluoroboron b-diketonate (BF 2 bdk) compounds are designed with multiple electrondonating groups to possess moderate k RISC values and are selected as luminescent dopants.T he matrices with carbonyl functional groups such as phenyl benzoate (PhB) have been found to interact with and perturb BF 2 bdk excited states by dipole-dipole interactions and thus enhance the intersystem crossing of BF 2 bdk excited states.T hrough dopant-matrix collaboration, the efficient TADF-type afterglow materials have been achieved to exhibit excellent processability into desired shapes and large-area films by melt casting, as well as aqueous afterglow dispersions for potential bioimaging applications.

In organic systems, it is very challenging to simultaneously achieve long afterglow lifetimes (τAG) and high afterglow efficiency (ΦAG). Here, luminescent dopants which feature a small rate of phosphorescence decay (kP) and modest rate of reverse intersystem crossing (kRISC) are designed and knr + kq values (nonradiative decay and quenching) of triplet excited states are suppressed by all means that include increasing molecular rigidity of luminescent dopants, screening organic matrices to strongly inhibit intramolecular motions of luminescent dopants, and deuteration of the luminescent dopants. Organic matrices are selected with large dipole moments to stabilize the singlet excited states of luminescent dopants via dipole–dipole interactions, reduce singlet–triplet splitting energy, and thus enhance ΦISC, leading to significant population of triplet excited states. Thermally activated delayed fluorescence mechanism is also used with modest kRISC to harvest triplet energies, significantly improve ΦAG to 64%, and maintain long τAG > 1.0 s. The obtained materials display intense afterglow brightness, excellent processability, and temperature‐sensing function.

Due to the energy gap law, the direct fabrication of efficient organic afterglow materials with long emission wavelengths at ambient conditions remains challenging. Here, luminescent dopants with moderate k RISC values of 10 0 -10 1 s −1 are designed to harvest triplet energies, simultaneously improving afterglow efficiency and maintaining emission lifetimes >0.1 s. Organic matrices with large dipole moments are selected to populate the triplet excited states of the luminescent dopants and suppress their nonradiative decay and quenching. The dopant-matrix systems exhibit TADF-type organic afterglow with quantum efficiency of 20% to 60% and emission wavelengths exceeding 600 nm. Because of their singlet excited state nature, the TADF-type afterglow emitters can efficiently transfer excited energy to rhodamine B or cyanine 5.5 fluorescence dyes for the construction of red and near-infrared afterglow materials which display promising bioimaging applications.