Pyrimidine-based twisted donor–acceptor delayed fluorescence molecules: a new universal platform for highly efficient blue electroluminescence

Deep-blue emitters that can harvest both singlet and triplet excited states to give high electron-to-photon conversion efficiencies are highly desired for applications in full-color displays and white lighting devices based on organic light-emitting diodes (OLEDs). Thermally activated delayed fluorescence (TADF) molecules based on highly twisted donor–acceptor (D–A) configurations are promising emitting dopants for the construction of efficient deep-blue OLEDs. In this study, a simple and versatile D–A system combining acridan-based donors and pyrimidine-based acceptors has been developed as a new platform for high-efficiency deep-blue TADF emitters. The designed pre-twisted acridan–pyrimidine D–A molecules exhibit small singlet–triplet energy splitting and high photoluminescence quantum yields, functioning as efficient deep-blue TADF emitters. The OLEDs utilizing these TADF emitters display bright blue electroluminescence with external quantum efficiencies of up to 20.4%, maximum current efficiencies of 41.7 cd A(–1), maximum power efficiencies of 37.2 lm W(–1), and color coordinates of (0.16, 0.23). The design strategy featuring such acridan–pyrimidine D–A motifs can offer great prospects for further developing high-performance deep-blue TADF emitters and TADF-OLEDs.