Orange-Red Thermally Activated Delayed Fluorescence Conjugated Polymers toward Highly Efficient Solution-Processable Red and White OLEDs

Due to the difficulty in achieving a suitable match between blue emitters and orange-red thermally activated delayed fluorescence (TADF) polymers, the development of solution-processable white organic light-emitting diodes (OLEDs) based on TADF polymers remains a significant challenge. Herein, a series of orange-red TADF polymers are developed using a strategy involving embedding the acceptor of quinoxaline-6,7-dicarbonitrile (QC) into the backbone and attaching the donor triphenylamine (T) with long alkyl chains as pendants. The synthesized polymers PCzTQCx exhibit orange-red emissions with emission peaks ranging from 571 to 621 nm. Non-doped, solution-processable organic light-emitting diode (OLED) devices based on these polymers exhibit pure white emission with a high color rendering index (CRI) of 80, achieved by using a TADF polymer with a low content of the TQC unit. In addition, warm white emission with a maximum external quantum efficiency (EQEmax) of 14.3%, CRI of 54 and red emission with an EQEmax of 9.3% and an emission peak at 609 nm can also be achieved. Through combination with a blue TADF small-molecule emitter, the single-emissive layer doped devices achieve warm white emission with EQEmax of 15.7%, luminance of 4325 cd m–2, and CRI of 64.