Polymerization could be a feasible method to overcome the rigid structure induced self-quenching effect in conventional thermally activated delayed fluorescence (TADF) emitters. Despite steady progress in TADF polymer research, developing an efficient red TADF polymer still remains a great challenge because of the large non-radiative internal conversion rate governed by the energy gap law. Herein, a novel strategy for constructing a red TADF conjugated polymer is presented by means of embedding quinoxaline-6,7-dicarbonitrile (QC) as an acceptor into a polycarbazole (PCz) backbone and attaching donor 9,10-dihydroacridine (A) as a pendant. The obtained polymers PCzAQCx with the appropriate molar content of the AQC unit (x ≥ 0.5) exhibit efficient TADF features with a dominant emissive peak at 627−661 nm and a photoluminescence quantum yield of up to 76% in neat film. The non-doped electroluminescent devices with the poly mers produce red emissions with a maximum external quantum efficiency (EQE) of up to 12.5% and the emission peak at 620 nm, which represents state-of-the-art performance for solution-processed devices based on red TADF polymers. Furthermore, combined with a blue TADF emitter, the bright white devices with tunable spectra cover the whole visible-near infrared range from 400 to 900 nm and a record-high EQE of up to 22.4% is achievable.

A sandwich-like chromophore, composed of two donors and an inserted acceptor, is hitched onto a single carbazole to yield an efficient TADF emitter with excellent electroluminescent performance.