An efficient thermally activated delayed fluorophore featuring an oxygen-locked azaryl ketone acceptor.

Thermally activated delayed fluorescence (TADF) dyes are promising for applications like bioimaging, sensing, and optoelectronic devices due to their efficient exciton utilization without noble metals, making them ideal for organic light-emitting diodes (OLEDs). In this contribution, we introduce a new TADF emitter, 3-(9,9-dimethylacridin-10(9 H)-yl)-12 H -chromeno[2,3- b ]quinolin-12-one (CQLO-DMAC), which incorporates an intramolecular oxygen-locked azaryl ketone acceptor, CQLO. This design enhances molecular rigidity and electron-accepting strength. The CQLO-DMAC compound, featuring a bulky donor, shows significant intramolecular charge transfer and TADF emission. Comprehensive analyses, including spectroscopic studies and theoretical calculations, reveal high luminescence efficiency and reduced non-radiative losses. Utilizing CQLO-DMAC in OLEDs, we achieved a green-yellow emission peak at 548 nm and a maximum external quantum efficiency of 17.4 %. The findings highlight the potential of CQLQ as a highly effective acceptor in designing of TADF electroluminescent dyes. [Display omitted] • An oxygen-locked azaryl ketone acceptor CQLO is designed for constructing TADF emitter (CQLO-DMAC). • CQLO-DMAC exhibits notable TADF properties, facilitating efficient triplet-to-singlet spin conversion. • CQLO-DMAC demonstrates bright TADF emission with a decent PLQY of 72 %. • High electroluminescence efficiency with an EQE of up to 17.4 % are demonstrated. [ABSTRACT FROM AUTHOR]