Deep-red TADF dendronized polymer for efficient non-doped solution-processed OLEDs

Abstract

Significant progress has been made in red thermally activated delayed fluorescence (TADF) emitters, but efficient solution-processable deep-red TADF polymers and their non-doped organic light-emitting diodes (OLEDs) are rarely reported. A novel deep-red TADF dendronized polymer PNAI-AcCz was synthesized to address this issue. First, the acridan donor was encapsulated by 3,6-di-tert-butylcarbazole via conjugated linkage to raise the highest occupied molecular orbital (HOMO) energy level and decrease aggregation caused quenching; then a non-conjugated carbazole connects the 1,8-naphthalimide acceptor to increase the solubility; finally, a linear dendronized copolymer was obtained by homopolymerization with an alkyl backbone as the main chains. The highly twisted donor–acceptor architecture leads to a small singlet–triplet energy gap of 0.015 eV, high photoluminescence quantum yield of 15%, and short delayed fluorescence lifetime of 4.20 μs. The non-doped solution-processed OLED based on PNAI-AcCz achieved a high EQE of 2.6% with a deep-red emission peak at 659 nm, which is the highest EQE value reported to date in the non-doped solution-processed deep-red TADF OLEDs.