Intramolecular Sensitization Assisting High-Efficiency TADF Conjugated Polymers with Accelerating Exciton Spin Flip for Solution-Processed Electroluminescent Devices

Thermally activated delayed fluorescence (TADF) conjugated polymers have attracted a lot of attention for their potential to produce flexible display devices. However, insufficient energy transfer from the host to TADF units will result in exciton–exciton annihilation and reduced device efficiency. To address these problems, an intramolecular sensitization strategy is employed in this work in which the spin flip of a triplet exciton can be accelerated by the intermediation of TADF sensitization units in polymers. By regulating the ratio of each polymeric component, excellent photophysical properties can be achieved with a photoluminescence quantum yield of 86% and a high rate of reverse intersystem crossing of 6.3 × 105 s–1. Moreover, the solution-processed polymer-based organic light-emitting diodes can achieve an attractive external quantum efficiency of 21.02% due to the effective utilization of triplet excitons. Overall, this research validates the feasibility of an intramolecular sensitization strategy for restraining exciton annihilation, thus providing a promising pathway for designing high-performance conjugated TADF polymers.