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A new narrowband thermally activated delayed fluorescence emitter, PhCzBN-PO, was developed by incorporating the diphenylphosphine oxide (DPPO) group into a multi-resonance core. The unique properties of DPPO enabled PhCzBN-PO to achieve pure green emission and a nonplanar structure. The resulting electroluminescent devices achieved high external quantum efficiencies up to 32.4% with extremely low efficiency roll-off and pure-green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.24, 0.67). [ABSTRACT FROM AUTHOR]

The development of blue thermally activated delayed fluorescence (TADF) emitters that can simultaneously achieve narrowband emission, high efficiency, and low efficiency roll-off in organic light-emitting diodes (OLEDs) remains a significant challenge. In this study, we present the successful design and synthesis of a series of TADF emitters by directly incorporating an electron donor into a boron/nitrogen/oxygen ternary doped multiple resonance (MR) skeleton. By carefully manipulating the donor strength, we were able to induce a long-range charge transfer triplet state to accelerate the reverse intersystem crossing (RISC) process. Meanwhile, the MR character of the first singlet excited state was preserved. As a result, the optimized emitter not only maintained the intrinsically excellent properties of the MR-TADF skeleton, such as deep-blue emission and high photoluminescence quantum yield of up to 89%, but also achieved a high RISC rate constant of 1.9 × 105 s−1. The corresponding deep-blue device exhibited a maximum external quantum efficiency (EQEmax) of 28.7%, with a full width at half maximum (FWHM) of only 36 nm and CIE coordinates approaching the NTSC blue standard. This study presents a simple yet effective approach for constructing high-performance deep-blue emitters for wide-color-gamut OLED displays. [ABSTRACT FROM AUTHOR]

A simple and novel furanyl acryl conjugated coumarin fluorophore was designed as an effective thioredoxin reductase (TrxR)-responding fluorescent probe by an activity-guided approach. Basically, the α,β-unsaturated ketone moiety in the probe structure could quench the fluorescence of the coumarin, but upon the covalent modification of TrxR, a significant fluorescence could be generated, which has been confirmed to be obviously selective over Trx, GSH, Cys and DTT.