Red thermally activated delayed fluorescence polymers containing 9H-thioxanthen-9-one-10,10-dioxide acceptor group as pendant or incorporated in backbone

A set of conjugated polymers PCzDPTx with carbazole/diphenylamine as backbone and 9H-thioxanthen-9-one-10,10-dioxide as the pendant, where DPT is 2-(4-(diphenylamino)-phenyl)-9H-thioxanthen-9-one-10,10-dioxide, and x = 1, 5, 10, 25 and 50, respectively, and two alternating copolymers PTCz and PTD with the backbone consisting of the acceptor unit 9H-thioxanthen-9-one-10,10-dioxide and the donor unit carbazole and diphenylamine groups have been respectively synthesized by Pd-catalyzed Suzuki coupling polycondensation. These polymers in films show long wavelength emissions of 573–629 nm with thermally activated delayed fluorescence (TADF) characteristics, confirmed by theory calculations and their transient PL decay spectra. Various organic light-emitting diodes (OLEDs) using the TADF polymers as emitters were fabricated by solution processing. The doped OLEDs based on the polymers PTD and PCzDPT50 with the 50% molar content of the DPT unit as the emitters produce the saturated red electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates (0.64, 0.36) and (0.63, 0.37), respectively. For the first time, a TADF polymer based sensitizer was utilized to further improve the electroluminescent performances of the TADF polymers with low quantum yields, e.g., at the maximum, 3.8-fold increase in the brightness and 1.8-fold increase in the external quantum efficiency were simultaneously demonstrated.