Constructing Thermally Activated Delayed Fluorescence Dendronized π-Conjugated Polymers for Efficient Non-Doped...

Highly efficient non-doped polymer light-emitting diodes (PLEDs) are under great challenge due to inherently structural disorder and unsatisfied carrier transporting capability of conventional linear polymeric emitters in aggregated state, severely hampering their application in cost-effective large-area display equipment and flexible wearable electronics. Herein, we propose the first case of thermally activated delayed fluorescence (TADF) dendronized π-conjugated polymers (DCPs) that involve embedding TADF moiety into π-conjugated backbones and grafting bulk dendritic substituent group onto sidechain. Due to the steric shielding effect of peripheral dendrons on TADF emission core, the inherent exciton aggregation-induced concentration quenching of chromophores can be effectively mitigated, and thus maintaining superior photoluminescence quantum yields of over 80% in neat films. Furthermore, the carrier motilities of second-generation TADF DCP emitter, PDB3Cz, can reach 1.02 × 10^-2 cm² V^-1 s^-1 together with preponderant horizontal dipole ratios of 80%, which are derived from the vertically aligned conjugated backbones of TADF DCPs and extendedly paralleled pendant TADF moieties to the substrate, respectively. As a result, the solution-processed non-doped PLEDs based on PDB3Cz achieve state-of-the-art device performances with attractive maximum external quantum efficiency of 27.5%, which is the highest values among non-doped TADF PLEDs.