Boron–Nitrogen Covalent Bond‐Embedded Multiple Resonance Emitters: Synthesis Strategy, Molecular Design, and Optoelectronic Properties

Organic light-emitting diodes (OLEDs) are the core of next-generation display and lighting technologies, and their performance is highly dependent on luminescent materials. Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials have emerged as ideal candidates for high-color-purity and high-efficiency OLEDs due to their narrowband emission and sufficient exciton utilization efficiency. Recently, incorporating isoelectronic B─N covalent bonds into conventional B/N-doped MR-TADF skeletons has generated a new class of B─N bond-embedded MR-TADF materials. These materials not only simplify the complex synthesis process of traditional MR-TADF molecules and avoid the use of hazardous lithium reagents, but also provide a new dimension for the diversification of molecular structures and the precise regulation of optoelectronic properties. This review systematically summarizes the research progress of B─N bond-embedded MR-TADF materials and their OLEDs. First, from the synthesis strategy, the advantages and mechanism of amine-directed lithium-free borylation reaction are elaborated. Subsequently, focusing on molecular design, the effects of molecular structures on photophysical properties and device performances are discussed in detail from the aspects of π-conjugation extension, peripheral substituent engineering, heteroatom doping, and chirality engineering. Finally, it discusses challenges and future directions, aiming to provide valuable references for developing next-generation high-performance, high-color-purity OLED materials.