TADF deep-blue OLED with color index approaching Rec.2020 standard blue gamut achieved by a boron-based D–A type molecular skeleton.

The ultra-high definition (UHD) displays in the market require organic light-emitting diodes (OLEDs) to meet the Rec.2020 color gamut standard, while it is still challenging to exploit ultra-deep-blue emitters that satisfy such blue standard. Herein, by substituting tCz (3,6-di(tert -butyl)carbazole) donor unit on the robust BOC (8,8,12,12-tetramethyl-8,12-dihydro-4-oxa-3a2-boradibenzo[ cd , mn ]pyrene) acceptor unit with high structural rigidity and appropriate energy levels, a novel boron-based D–A type thermally activated delayed fluorescence (TADF) ultra-deep-blue emitter, namely, tCz-BOC , was readily designed and synthesized. Inheriting from its rigid organoboron core, the emitter presents ultra-deep-blue emission with narrow spectral full width at half maximum (FWHM) of 54 nm and high photoluminescence quantum yield up to 73.7%. Additionally, tCz-BOC can effectively harvest T 1 excitons through high-lying T 2 mediated reverse intersystem crossing process. As a consequence, the fabricated OLED based on tCz-BOC exhibits a satisfactory ultra-deep-blue emission with λ EL of 424 nm, narrow emission bandwidth with FWHM of 47 nm, excellent maximum external quantum efficiency (EQE max) of 13.9%, as well as the CIE y coordinate of 0.047, which is fairly close to the Rec.2020 blue color gamut. A novel deep-blue thermally activated delayed fluorescence molecule. [Display omitted] • A robust TADF emitter tCz-BOC with ultra-deep-blue emission peaked at 428 nm and a narrow FWHM of 47 nm was obtained. • An excellent CIE y coordinate of 0.047 which is close to the Rec.2020 blue color gamut was achieved in its OLED. • The EQE max of the OLED was as high as 13.9%. [ABSTRACT FROM AUTHOR]