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It is of great strategic significance to develop highly efficient narrowband organic electroluminescent materials that can be utilized to manufacture ultra‐high‐definition (UHD) displays and meet or approach the requirements of Broadcast Television 2020 (B.T.2020) color gamut standards. This motif poses challenges for molecular design and synthesis, especially for developing generality, diversity, scalability, and robustness of molecular structures. The emergence of multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters has ingeniously solved the problems and demonstrated bright application prospects in the field of UHD displays, sparking a research boom. This Minireview summarizes the research endeavors of narrowband organic electroluminescent materials, with emphasis on the tremendous contribution of frontier molecular orbital engineering (FMOE) strategy. It combines the outstanding advantages of MR framework and donor‐acceptor (D−A) structure, and can achieve red‐shift and narrowband emission simultaneously, which is of great significance in the development of long‐wavelength narrowband emitters with emission maxima especially exceeding 500 nm. We hope that this Minireview would provide some inspiration for what could transpire in the future. [ABSTRACT FROM AUTHOR]

Advanced multiple resonance induced thermally activated delayed fluorescence (MR‐TADF) emitters have emerged as a privileged motif for applications in organic light‐emitting diodes (OLEDs), because they furnish highly tunable TADF characteristics and high color purity emission. Herein, based on the unique nitrogen‐atom embedding molecular engineering (NEME) strategy, a series of compounds BN‐TP‐Nx (x=1, 2, 3, 4) have been customized. The nitrogen‐atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly‐constructed emitters have demonstrated the precise regulation of emission maxima of MR‐TADF emitters to meet the actual industrial demand, and further enormously enriched the MR‐TADF molecular reservoir. The BN‐TP‐N3‐based OLED exhibits ultrapure green emission, with peak of 524 nm, full‐width at half‐maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3 %. [ABSTRACT FROM AUTHOR]

Multiple resonance thermally activated delayed fluorescence (MR‐TADF) compounds have set off an upsurge of research because of their tremendous application prospects in the field of wide color gamut display. Herein, we propose a novel MR‐TADF molecular construction paradigm based on polycyclization of the multiple resonance parent core, and construct a representative multiple resonance polycyclic aromatic hydrocarbon (MR‐PAH) based on the para‐alignment of boron and nitrogen atoms into a six‐membered ring (p‐BNR). Through the retrosynthesis analysis, a concise synthesis strategy with wide applicability has been proposed, encompassing programmed sequential boron esterification, Suzuki coupling and Scholl oxidative coupling. The target model molecule BN‐TP shows green fluorescence with an emission peak at 523 nm and a narrow full‐width at half‐maximum (FWHM) of 34 nm. The organic light‐emitting diode (OLED) employing BN‐TP as an emitter exhibits ultrapure green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.26, 0.70), and achieves a maximum external quantum efficiency (EQE) of 35.1 %. [ABSTRACT FROM AUTHOR]

The design and synthesis of organic materials with a narrow emission band in the longer wavelength region beyond 510 nm remain a great challenge. For constructing narrowband green emitters, we propose a unique molecular design strategy based on frontier molecular orbital engineering (FMOE), which can integrate the advantages of a twisted donor–acceptor (D‐A) structure and a multiple resonance (MR) delayed fluorescence skeleton. Attaching an auxiliary donor to a MR skeleton leads to a novel molecule with twisted D‐A and MR structure characteristics. Importantly, a remarkable red‐shift of the emission maximum and a narrowband spectrum are achieved simultaneously. The target molecule has been employed as an emitter to fabricate green organic light‐emitting diodes (OLEDs) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.69) and a maximum external quantum efficiency (EQE) of 27.0 %. [ABSTRACT FROM AUTHOR]

A novel molecular design paradigm for developing narrowband electroluminescence emitter composed of multiple resonance (MR) framework and organometallic complex is proposed here, and the solution-processed organic light-emitting diode (OLED) employing the target organometallic platinum (II) complex BNCPPt as an efficient dopant emitter exhibits green CIE coordinates (0.22, 0.63) with narrow FWHM (35 nm), and achieves maximum EQE of 13.5% with very low efficiency roll-off (4.4%) at 1000cd/m−2(-|-). [Display omitted] • A novel narrowband organometallic complex EL emitter composed of multiple resonance (MR) framework is developed. • A simple solution-processed fabrication process for preparing high-performance OLED has been achieved. • Quite high maximum EQE >13.5% with very low efficiency roll-off (4.4%) at 1000 cd m−2 has been realized. The narrowband emission required by wide color gamut display is an extremely important research topic for any luminescence mechanism, which has made significant progress in traditional fluorescence and thermally activated delayed fluorescence (TADF) based on purely organic compounds, but is far from mature in organometallic complexes. Herein, we propose a feasible molecular design paradigm for constructing the desirable organic electroluminescence (EL) emitter with narrowband emission by integrating an original multiple resonance TADF (MR-TADF) fragment into the classical platinum (II) complex. The solution-processed organic light-emitting diode (OLED) by employing the target model platinum (II) complex BNCPPt as the dopant emitter shows light green emission with a peak of 507 nm and narrow full-width at half-maximum (FWHM) of 35 nm, which achieves a maximum external quantum efficiency (EQE) of 13.5% with very low efficiency roll-off of 4.4% at 1000 cd m−2. [ABSTRACT FROM AUTHOR]