Realizing highly efficient deep-blue organic light-emitting diodes towards Rec.2020 chromaticity by restricting the vibration of the molecular framework

Deep-blue organic light-emitting diodes (OLEDs) with narrow emission spectra and high efficiency, meeting the Rec.2020 standard, hold significant promise in the realm of 4K/8K ultrahigh-definition displays. However, the development of light-emitting materials exhibiting both narrowband emission and high efficiency, particularly in the realm of deep-blue thermally activated delayed fluorescence (TADF), confronts substantial challenges. Herein, a novel deep-blue TADF emitter, named BOC-PSi , was designed by integrating a rigid B-heterotriangulene acceptor (A) with a rigid phenazasiline donor (D). The replacement of a sp 3 carbon atom with a sp 3 silicon atom in the D moiety helps to restrict the low-frequency bending vibration throughout the entire D-A molecular backbone, while concurrently accelerating the multi-channel reverse intersystem crossing (RISC) processes. Notably, OLEDs using the BOC-PSi emitter exhibit exceptional performance, with a high maximum external quantum efficiency (EQE max ) approaching 20%, and a superior color purity closely aligning with the Rec.2020 blue standard. A deep blue TADF emitter composed of rigid D and A units was developed. BOC-PSi -based OLED exhibited not only an impressive EQE max approaching 20%, but also a superior color purity approaching the Rec.2020 blue standard.