Narrowband emissive polycyclic aromatic heterocycles (PAHs) featuring multiple resonance thermally‐activated delayed fluorescence (MR‐TADF) are capable of achieving high color purity with high exciton utilization efficiency via reverse intersystem crossing (RISC). However, thermally‐activated RISC remains the rate‐limiting step in MR‐TADF molecules due to the typically large singlet and triplet energy gap (Δ E ST ) and weak spin‐orbital coupling. To overcome this challenge, we introduce three carbonyl‐containing organoboron PAHs doped with selenium atoms (pSeXBNO, 1pSeXBN, and pSeXBN) for the first time. Introducing single or dual selenium‐embedded carbonyl heterocycles into the MR core enables significant orbital delocalization of carbonyls, resulting in small Δ E ST and ultrafast RISC rates of 7.5 × 10 6 s −1 for pSeXBNO, 1.5 × 10 7 s −1 for 1pSeXBN, and 4.8 × 10 7 s −1 for pSeXBN. The non‐sensitized OLED employing pSeXBN achieves an emission peak at 478 nm with a narrow bandwidth of 28 nm, along with a maximum external quantum efficiency (EQE) of 32.6% and retaining 28.4% at 1000 cd m −2 , representing state‐of‐the‐art performance for blue MR‐TADF materials. Moreover, bi‐color white OLED employing pSeXBN exhibits excellent performance with a maximum EQE of 30.9% and 23.2% retained at 1000 cd m −2 . These advances demonstrate the role of carbonyl here is of significant guidance in forwarding narrowband blue materials.

Bulky substituents with large steric hindrance are usually incorporated into the narrowband emitters for organic light-emitting diodes (OLEDs) to mitigate molecular aggregation. However, their impact on vibronic coupling, which also critically determines emission color purity, has rarely been elucidated. Herein, two boron-nitrogen multiple resonance thermally activated delayed fluorescence emitters, DTMCzBN and TTMCzBN, were rationally designed by introducing two or three tetramethyl-carbazole (TMCz) groups. These TMCz substituents not only disrupt it-it stacking, effectively suppressing the formation of emissive dimers, but also suppress vibronic coupling, leading to enlarged energy separations between vibronic transitions and reduced 0-1 transition intensity. Benefiting from this dual effect, DTMCzBN and TTMCzBN exhibit exceptional narrowband emissions with full widths at half maximum of 19.8 and 17.0 nm, respectively, while maintaining emission maxima at 459 and 456 nm in solution. Corresponding OLEDs deliver outstanding performance, achieving maximum external quantum efficiencies of 32.1% for DTMCzBN with CIE coordinates of (0.13, 0.10), and 26.1% for TTMCzBN with CIE coordinates of (0.138, 0.067), approaching the NTSC blue standard. These findings highlight multiple steric substitutions as an effective molecular design strategy that cooperatively suppresses it-it stacking and vibronic coupling, promoting the development of next-generation deep-blue emitters for wide-color-gamut OLED displays.

Multiple resonance (MR) emitters with excellent color purity hold promise for high-performance organic light-emitting diodes (OLEDs), yet their practical applications face severe efficiency roll-off at high luminance due to inefficient triplet exciton utilization inherent in themselves. Herein, an energy-level ladder engineering strategy is presented to address this challenge. By introducing an electron-rich fragment into the MR framework, a locally excited (LE) intermediate energy level (T2) is constructed that facilitates rapid spin-flipping with reduced thermal activation energies. The synthesized emitter, tCzBNNOp, with pure green emission at 520 nm (CIE: (0.20, 0.72)), exhibits a remarkably high reverse intersystem crossing rate (k RISC = 1.45 & times; 106 s-1). Theoretical calculations and experimental data jointly reveal that the LE T2 state with large spin orbital coupling and a small energy difference between S1, creating an extra RISC channel. In the corresponding non-sensitized OLED devices, tCzBNNOp achieves a maximum external quantum efficiency (EQEmax) of 30.3% with an efficiency roll-off of only 12.5% at 1000 cd m-2, outperforming its structural analog in roll-off suppression. Moreover, the device retains an EQE of 16.6% at 5000 cd m-2 and demonstrated better operational stability. This work establishes energy-level ladder engineering as a powerful approach for developing high-efficiency MR-based OLEDs with suppressed efficiency roll-off.

ABSTRACT Heteroatom‐doped polycyclic aromatic hydrocarbons (PAHs) with special topological structures have garnered significant attention owing to the effective regulation of photophysical properties of emitters at the molecular level. Herein, we report the design and one‐pot synthesis of two heteroatom‐doped PAHs, namely 4BN with a twisted helical configuration and 3BN with a quasi‐planar configuration. Systematic structure‐property investigations reveal that molecular topology plays a decisive role in governing intrinsic electronic structures and intermolecular interactions. The quadruple‐borylated 4BN with rigid PAH skeleton effectively suppresses structural relaxation and electron‐vibrational coupling via manipulating the non‐bonding characteristics, thereby affording ultra‐narrowband emission. Consequently, for 4BN, the full widths at half maximum (FWHMs) as narrow as 13 nm in toluene solution and 14 nm in solution‐processed electroluminescence device are achieved, representing the narrowest FWHM reported to date for OLEDs based on multiple resonance (MR) emitters. Furthermore, in TADF‐assisted solution‐processed device, the emission spectrum slightly broadens to 15 nm with a maximum external quantum efficiency (EQE max ) of 18.9%. In sharp contrast, the triple‐borylated 3BN with quasi‐planar geometry shows enhanced π‐delocalization and stronger vibronic coupling, resulting in broader FWHM of 25 nm in TADF‐assisted solution‐processed devices with an EQE max of 19.8%.

Solution-processed organic light-emitting diodes (OLEDs) are attractive for cost-effective optoelectronic devices, but their performance is constrained by poor control over transition dipole moment orientation, which limits light out-coupling efficiency. Here, we present a rational molecular design strategy to address these challenges by developing a novel thermally activated delayed fluorescence (TADF) emitter, 3SFAc-TRZ, featuring a rigid triazine core, multiple spiro-acridine donor units, and peripheral fluorene substituents with solubilizing alkyl chains. This design affords a planar molecular framework with degenerate frontier orbitals, enabling strong charge-transfer character and an exceptionally small singlet-triplet energy gap. Therefore, efficient TADF with a high photoluminescence quantum yield of 76% and a rapid reverse intersystem crossing is achieved in films. Importantly, 3SFAc-TRZ exhibits remarkable horizontal dipole ratios of 80% and 76% in spin-coated neat and doped films. When employed in solution-processed OLEDs, the emitter achieves a high maximum external quantum efficiency of 30.03% with well suppressed efficiency roll-off. These results highlight the effectiveness of the molecular design strategy in enhancing horizontal dipole orientation, showing great promise for advancing high-performance solution processable OLEDs.

ABSTRACT Developing high‐color‐purity deep‐blue emitters that meet the BT.2020 standard remains a critical challenge in organic light‐emitting diodes (OLEDs). Herein, a stepwise molecular engineering strategy for simultaneously accelerating reverse intersystem crossing rate ( k RISC ) and narrowing full‐width at half maxima (FWHM) is proposed for deep‐blue materials. By sequentially enhancing molecular rigidity, strengthening resonant strength, and completing molecular symmetry, a deep‐blue emitter (DBNDICz), constructed on modified diboron multiple‐resonance scaffold, is developed with peak of 452 nm, ultra‐narrow FWHM of 15 nm (0.08 eV) and k RISC of 3.0 × 10 5 s − 1 . The dominant υ 0‐0 transition character of DBNDICz produces a Commission Internationale de I’Éclairage (CIE) coordinates of (0.144, 0.060). Moreover, the expanded conjugated skeleton facilitates horizontal dipole orientation of 93%, leading to a high maximum external quantum efficiency (EQE max ) of 24.2% in bottom‐emitting OLEDs. Impressively, top‐emitting OLED achieves a record‐setting blue index of 514 cd A − 1 CIEy − 1 with CIE (0.146, 0.036) and EQE max of 45.2%, establishing a benchmark for state‐of‐the‐art deep‐blue devices. Additionally, an operational lifetime (LT 50 ) of 154.2 h is achieved in an anthracene‐based host. These results represent one of the best performances reported for deep‐blue OLEDs with CIEy≤ 0.06, providing a robust design paradigm for high‐performance narrowband deep‐blue TADF emitters.

The development of state-of-the-art organic light-emitting diode (OLED) displays still faces two unavoidable challenges: lowering power consumption and achieving long operational stability. These difficulties originate largely from the complex multilayer OLED architecture, where several organic/organic and organic/inorganic heterointerfaces critically influence charge injection, carrier balance, and long-term stability. To address these interface-related issues, we designed a multifunctional electron-transport material, DPmPy-DBF1, that enables efficient electron injection when combined with silver (Ag). DPmPy-DBF1 integrates a dipyrimidylpyridine (DPmPy) unit, capable of strong Ag coordination, with a thermally robust dibenzofuran (DBF) unit through a meta-phenylene linker. This design suppresses excessive conjugation, increases conformational diversity, and produces an amorphous thin film with a high triplet energy of 2.9 eV. The material exhibits excellent thermal stability, including a glass-transition temperature of 127 degrees C, and favorable energy alignment that mitigates electron accumulation at organic/organic interfaces. When doped with Ag, DPmPy-DBF1 demonstrates superior electron-injection ability, as confirmed by UPS analysis and electron-only devices. A green phosphorescent OLED using DPmPy-DBF1 as a hole-blocking, electron-transport, and electron-injection layer achieves a low turn-on voltage of 2.18 V, a maximum EQE of 20.7%, and an extended operational lifetime (LT70 = 6389 h at 1000 cd m-2). These results highlight DPmPy-DBF1 as a promising multifunctional material for next-generation OLEDs.

Metal halide perovskites show promise for light-emitting diodes (LEDs) owing to their facile manufacture and excellent optoelectronic performance, including high color purity and high carrier mobility, while the photophysical processes remain partially obscure. Herein, by introducing 18-crown-6 and tBO-Br as dual passivation agents, quasi-2D phase perovskites are suppressed through controlled nucleation and crystal growth, yielding high-quality quasi-nanocrystalline films with improved crystallinity and isotropic orientation. Synergistic passivation reduces trap-assisted non-radiative recombination, achieving a photoluminescence quantum yield of 93.5% at 520 nm and enhanced carrier lifetimes. Notably, dual emission with a shoulder peak at 535 nm and directional energy transfer with long-lived delayed component at low temperature reveal dynamic equilibrium between free excitons and self-trapped excitons (STEs) governed by strong exciton-phonon coupling. Finally, benefiting from suppressed STEs formation and better energy alignment, green perovskite LEDs treated with dual additives achieve a high external quantum efficiency of 29.5%, high luminance of 59232 cd m-2, and a commendable operating half-lifetime of 10.81 hours at an initial brightness of 1000 cd m-2 while maintaining low efficiency roll-off. The observation of the dual emission and long-lived delayed components, coupled with insights into STEs, provides a profound and comprehensive understanding of the fundamental carrier behavior in perovskite emitters.

Boron‐based multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have attracted considerable attention as a promising approach for achieving high color purity and ≈100% internal quantum efficiency in organic light‐emitting devices (OLEDs). Although many MR‐TADF emitters have been developed to date, achieving high external quantum efficiency (EQE), it remains challenging to simultaneously realize long operational lifetimes, especially in blue OLEDs with CIE y <0.20. In this study, novel blue MR‐TADF emitters named DPSi‐R‐BN derivatives are designed to address this issue. By introducing a cross‐linked structure into the DABNA‐1 skeleton via a silicon bridge and enhancing the bond dissociation energy (BDE) of the fragile carbon–nitrogen bond, the electrochemical stability of the emitters is successfully improved. The resulting blue OLED exhibitsed an EQE of 24.5%, a narrow full width at half maximum of 24 nm, and CIE coordinates of (0.137, 0.175). Most notably, the device shows a 1.4‑fold improvement in operational lifetime (LT 80 = 373/111 h at 500/1000 cd m −2 ) compared to the conventional t‐DABNA ‐based device.

While trap states are traditionally considered as performance-limiting defects in organic light-emitting diodes (OLEDs), this work presents a dual-trap exciplex heterojunction system that strategically engineers trap states to enhance device performance. The tailored electron (4CzTPNBu in p-type host) and hole (PO-01 in n-type host) traps are employed for interfacial bidirectional carrier capture synergistically without compromising carrier transport in the exciplex heterojunction system. This innovative design converts interfacial traps into immediate radiative trap-assisted recombination (TAR) centers with significant expansion of exciton recombination zone, simultaneously preventing carrier transport imbalance and charge accumulation. The yellow OLEDs demonstrate cutting-edge 33.9% external quantum efficiency (EQE), and 453.6 h operational lifetime (LT90 at 1000 cd m-2) representing a ninefold enhancement over conventional architectures. Through ideality factor analysis complemented by single-carrier device and transient electroluminescence studies, the fundamental charge transport physics and trap-mediated dynamics are unraveled. Implementation of dual-trap in narrow-band hyperfluorescent systems also enables EQEs surpassing 36% and mitigated efficiency roll-off, along with prolonged LT90 of 178.7 h. The dual-trap methodology successfully merges the advantages for twin emitters and achieves a win-win scenario for efficiency and lifetime, providing a promising paradigm for future high-performance OLED development.

To address the bottlenecks of high cost, complex process, and functional limitations in thin-film encapsulation for top-emitting organic light-emitting diodes (TEOLEDs), we develop an ultra-thin multifunctional passivation patch film (MPPF) based on low-temperature imprinting technology. The MPPF employs a tri-layer synergistic design that integrates moisture barrier, hygroscopicity, light extraction, adhesion, and flexibility, overcoming the constraints of conventional encapsulation. The hydrophobic light-extraction layer utilizes 3 wt.% silicon dioxide nanoparticle to induce submicron-scale scattering, achieving 78.9 % transmittance and 78.66 % haze at 550 nm, combined with a superhydrophobic surface (water contact angle is 159.6 degrees) to block water penetration. The flexible support layer of MPPF adopts ultra-thin glass (50 mu m thickness, bending radius <3 mm, water vapor transmission rate is 10(-6) g/m(2)/day). The hygroscopic-adhesive layer incorporates 2 wt.% CaO-doped polyisobutylene, achieving 95.5 % transmittance at 550 nm while providing high adhesion strength (200 N at 27 degrees C) and active moisture absorption (2.25 mg/cm(3) after 6 h at 60 degrees C/100 % relative humidity), effectively suppressing lateral moisture and oxygen permeation. The results demonstrate significant performance improvements in MPPF-encapsulated TEOLEDs, achieving a 39.7 % enhancement in light extraction efficiency and an external quantum efficiency of 22.89 %. Meanwhile, the full width at half maximum (FWHM) was narrowed down to 15.15 nm, with an 18.5 % expansion in color gamut area and suppressed viewing-angle-dependent color shift (FWHM variation <0.5 nm at 0-60 degrees). Moreover, the luminance drops to 50 % of the initial luminance achieves 575 h, approaching that of the glass encapsulated devices. This work presents an innovative encapsulation solution through multifunctional integration and low-temperature processing, offering high efficiency, extended longevity, wide viewing angles, and stable color purity for ultra-thin flexible displays.

Top-emitting organic light-emitting diodes (TEOLEDs) based on metal/transparent conductive oxide composite anodes, which were Al/ITO and Ag/ITO, were studied. The microcavity effect was optimized by adjusting the microcavity thickness and microcavity order to achieve high color gamut RGB monochromatic light display. Through mathematical modeling and spectral simulation, TEOLEDs with different microcavity structures were designed. The results show that the full width at half maximum and the color purity of the light of the TEOLED based on the second-order microcavity were significantly optimized compared to those of the TEOLED based on the first-order microcavity. Meanwhile, the TEOLEDs based on the Ag/ITO composite electrode exhibits better optoelectronic performance, with the significantly enhanced external quantum efficiency up to 19.40 %, narrower full width at half maximum down to 20 nm, and improved color purity. The corresponding red, green, and blue TEOLEDs have achieved excellent color coordinates (0.697, 0.301), (0.154, 0.769), and (0.139, 0.050), and the color gamut area of the device has reached 172.4 % of the color gamut area of the bottom-emitting OLED, 125.6 % of the National Television System Committee standard color gamut, and 93.8 % of the ITU-R Recommendation BT.2020 standard color gamut, demonstrating a significant achievement in high color gamut display performance.

Ubiquitous metal complexes with superior thermally activated delayed fluorescence (TADF) properties have emerged as promising candidates for light‐emitting materials due to their earth‐abundant nature and tunable optoelectronic characteristics. However, metal complexation often results in unfavorable solubility issues, which limit their application in solution‐processed OLEDs. Moreover, achieving a short‐delayed lifetime (τ d ) is essential for further enhancing device performance with a small efficiency roll‐off. In this work, a highly soluble and luminescent aluminum(III) complex exhibiting exceptional TADF characteristics is presented through precise regulation of their electronic structures. This complex demonstrates high solubility in common organic solvents while maintaining excellent photofunctional properties, such as PLQY values approaching unity, reduced aggregation‐caused quenching (ACQ), radiative decay rate constant ( k r ) exceeding 10 7 s −1 , impressive TADF performance with reverse intersystem crossing rate ( k RISC ) over 10 6 s −1 and τ d below 1 µs. Consequently, a novel aluminum(III) complex used as a sensitizer achieves an external quantum efficiency exceeding 20%, a full width at half maximum of 52 nm, and CIE coordinates of (0.31, 0.64) in solution‐processed hyperfluorescent OLEDs.

Although multi-resonance thermally activated delayed fluorescent (MR-TADF) emitters simultaneously achieve high color purity and high efficiency in organic light-emitting devices (OLEDs), MR-TADF-based OLEDs suffer from severe efficiency roll-off and lifetime issues for practical application. To overcome these issues, a key solution is hyper OLED technology sensitized by TADF or phosphorescent emitters. In this study, a series of π-extended phenoxazine-based asymmetric MR-TADF emitters for long lifetime, low-power consumption, and narrow emission band green OLEDs is developed. As a sensitizer, a well-known phosphorescent emitter is used, fac -tris(2-phenylpyridinato-C2,N)iridium(III) [Ir(ppy) 3 ]. Consequently, these MR-TADF emitters achieve hyper OLEDs with a power efficiency of 150 lm W −1 , an external quantum efficiency of 27%, and a long lifetime LT 95 of over 3000 h at high brightness of 1000 cdm −2 . These performances are among the best in scientific literature.

A green hyper OLED with CIE (0.31, 0.66), 159.9 lm W−1, and LT95/90 lifetimes of 600/2400 hours at 1000 cd m−2 was developed by preventing carrier trapping with MR-TADF emitter at hole-transporter/emission layer interface.

Although lambda 5-phosphinine derivatives are known as a promising class of blue fluorescent emitters, those photoluminescent quantum yield (PLQY) values have been reached up to 92 %, however, only a few examples have been explored as an emitter for blue organic light-emitting device (OLED), and the external quantum efficiency (EQE) has been below 2.4 % so far. In this study, we newly developed two types of blue lambda 5-phosphinine derivatives namely CN-COCF3 and CO2Me-CHO, and investigated the photophysical properties in the solid states. The photophysical analyses in solid state films suggested that the strong electron-accepting nature of these lambda 5-phosphinine derivatives caused the inferior PLQY values, and the exciplex formation with the host and neighboring materials should be avoided to improve the device efficiency. By choosing suitable host and neighboring materials with deep ionization potentials, we successfully realized efficient blue fluorescent OLEDs with EQE of over 4 % and CIE (0.14, 0.18). This is among the best in lambda 5-phosphinine-based blue OLEDs so far.

Polyethyleneimine (PEI) can reduce work function when applied to cathode surface and to improve the drive efficiency of various organic electronic devices. Clarifying the mechanism of the work function reduction is important in developing alternative materials with higher stability. In this paper, a PEI thin film coated on a ZnO layer using all-atom molecular dynamics simulations is analyzed. The simulations show that the entire PEI thin film induces an electrostatic potential shift of 0.30 eV, whose magnitude and sign are in good agreement with experiments. Further analysis reveals that there are two electric double layers (EDLs) at the ZnO/PEI interface and PEI/vacuum surface and that the latter plays a major role. The coil-shell conformation of PEI at the PEI/vacuum surface forms the outer EDL and reduces the work function. At the ZnO/PEI interface, on the other hand, the coil-shell conformation is less dominant because of the Zn-N interaction and the inner EDL causes a small increase of the work function. This dual EDL model is different from the single EDL model for self-assembled monolayers in that polymer conformations are essential. The report clarifies the novel polymer-specific mechanism of work function reduction and opens up the possibility of new cathode modifiers.

Although multi-resonance thermally activated delayed fluorescent (MR-TADF) emitters simultaneously achieve high color purity and high efficiency in organic light-emitting devices (OLEDs), MR-TADF-based OLEDs suffer from severe efficiency roll-off and lifetime issues for practical application. To overcome these issues, a key solution is hyper OLED technology sensitized by TADF or phosphorescent emitters. In this study, a series of pi-extended phenoxazine-based asymmetric MR-TADF emitters for long lifetime, low-power consumption, and narrow emission band green OLEDs is developed. As a sensitizer, a well-known phosphorescent emitter is used, fac-tris(2-phenylpyridinato-C2,N)iridium(III) [Ir(ppy)(3)]. Consequently, these MR-TADF emitters achieve hyper OLEDs with a power efficiency of 150 lmW(-1), an external quantum efficiency of 27%, and a long lifetime LT95 of over 3000 h at high brightness of 1000 cdm(-2). These performances are among the best in scientific literature.

In this study on perovskite solar cells (PVSCs), we incorporate N-benzylhydroxylamine (N-BzHoA) as an additive into the precursor solution. The addition of N-BzHoA suppressed the formation of unwanted PbI _2 and δ-phase perovskite without affecting the band gap, confirming uniform and large grains in the perovskite film. The fabricated inverted PVSCs exhibited remarkably improved properties compared to the control device, with a power conversion efficiency of 17.49%, reduced hysteresis, and more than 89% retention of the initial capacity after 100 h of light exposure. Thus, this study highlights the effectiveness of N-BzHoA as an effective additive for inverted PVSCs.

Although Earth-abundant, ubiquitous, metal-based thermally activated delayed fluorescence (TADF) complexes are among the most promising candidate materials for next-generation organic light-emitting devices (OLEDs), few complexes are explored. Herein, a highly emissive aluminum(III)-TADF complex-Al(MCzDBM)(3)-with three beta-diketone ligands is presented as a sensitizer for multiresonance (MR)-TADF emitters. This complex exhibited green emission with suitable photophysical functions as a sensitizer, such as a high photoluminescent quantum yield (PLQY) of up to 97% with reduced aggregation-caused quenching, a high radiative rate constant (k(r)) of 5.6 x 10(7) s(-1), and a short delayed lifetime (tau(d)) of 4.0 mu s in the solid state. A solution-processed Al(MCzDBM)(3)-based OLED exhibited an external quantum efficiency (EQE) of 23.6%. This complex sensitized a yellow MR-TADF emitter, yielding a near-unity PLQY, and is used to fabricate a solution-processed hyperfluorescent OLED with an EQE of 21.6% and full width at half maximum of 45 nm.