Constructing High-Efficiency Orange-Red Thermally Activated Delayed Fluorescence Polymers by Excited State Energy Levels Regulation via Backbone Engineering

摘要

Thermally activated delayed fluorescence (TADF) materials have attractedextensive attention because of their 100 theoretical exciton utilization.Solution-processable orange-red TADF polymers are one of indispensableparticipants. Herein, a series of orange-red TADF polymers withdibenzothiophene (DBT) and carbazole (Cz) units as joint backbones aresynthesized. Their performance can be successfully optimized by regulatingthe connection positions of DBT units through backbone engineering. It isfound that the pNAI37 series with DBT units embedded in the polymericbackbones at the 3, 7 sites display a better performance than those connectedat the 2, 8 sites. The optimal polymer, pNAI3705, exhibits a better excitedstate nature, leading to the photoluminescence quantum yield of 60.Consequently, pNAI3705 based organic light-emitting diodes reach amaximum external quantum efficiency of 20.16, and maintain 10.61 at500 cd m~(?2), which is in first tier among orange-red polymers. These resultsunambiguously suggest the potential application of the combined DBT and Czbackbones in TADF polymers. This design strategy may provide a versatileapproach for optimizing the properties of TADF polymers through backboneengineering.