Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have attracted considerable academic and industrial attention because of their narrowband emission, high photoluminescence quantum yields (PLQYs), and exceptional chemical and thermal stability. These characteristics make them highly promising for applications in ultra-high-definition (UHD) displays, as they enable organic light-emitting diodes (OLEDs) with high color purity, superior efficiency, and outstanding operational stability. Nevertheless, the development of highly efficient and stable deep-blue OLEDs remains a critical and unresolved challenge. Recent advances in blue MR-TADF emitters, based on boron/nitrogen-, nitrogen/carbonyl-, and indolocarbazole-type MR systems, have yielded exceptional performance, with full-width at half-maximum (FWHM) values below 30 nm and external quantum efficiencies (EQEs) exceeding 30%. Despite these achievements, persistent issues such as aggregation-caused quenching (ACQ), efficiency roll-off, and device stability continue to impede further progress in blue-emitting OLEDs. This review comprehensively summarizes recent developments in blue MR-TADF materials and devices, focusing on their molecular design strategies aimed at tuning emission color, mitigating ACQ, as well as improving device efficiency and operational lifetime. The discussed insights are expected to accelerate the development of high-performance, stable blue MR-TADF emitters for next-generation UHD display.

Perovskite light-emitting diodes have emerged as promising candidates for next-generation lighting and display technologies owing to their superior efficiency and high color purity. However, the perovskite active layers are highly sensitive to moisture and oxygen in ambient air, necessitating fabrication under protective atmospheres, which would increase production costs and limit industrial scalability. Moreover, the use of toxic antisolvents poses additional environmental concerns. Here, we report air-processable reduced-dimensional perovskites enabled by a dual passivation strategy to reduce the defect density and improve the film quality. Specifically, ammonium trifluoromethanesulfonate was incorporated into the perovskite precursor solution, while tris(4-fluorophenyl)phosphine oxide was introduced via an eco-friendly antisolvent (ethyl acetate). These passivating agents effectively coordinate with the perovskite framework, suppressing defect formation. The resulting devices achieved a maximum external quantum efficiency of 13.9% and enhanced operating stability and economic efficiency, thereby bringing an important step toward the commercialization of perovskite light-emitting diodes in optoelectronic applications.

Abstract Perovskite quantum dot light-emitting diodes (QLEDs) offer superior efficiency and high colour purity, making them promising candidates for next-generation lighting and display technologies. However, fabricating the emissive perovskite quantum dot (QD) layer typically requires a protective atmosphere due to its air sensitivity, thereby increasing production costs and limiting industrial scalability. Here, we propose an ion-pair pinning strategy by using tetraalkylammonium triflate (NR4OTf) to enable ambient-air processing of formamidinium lead bromide (FAPbBr3) QD films. The trifluoromethanesulfonic acid anions (OTf−) hydrogen bond with FA+, inhibiting its detachment and passivating the uncoordinated Pb2+, while the tetraalkylammonium cations (NR4 +) serve as X-type ligands to inhibit deprotonation. This dual ion-pair pinning effect stabilises the QD lattice and provides surface resistance to moisture and oxygen, thereby improving the uniformity, stability, and optoelectronic performance of air-processed QD films. The as-constructed air-processed QLED achieves a high external quantum efficiency (EQE) of 21.3% and a peak luminance of over 3 × 104 cd m−2 at 529 nm with Rec. 2020 compliance (EQE of 23.9% and luminance of over 8 × 104 cd m−2 for the N2-processed QLED). Our work eliminates the reliance on inert gas protection in perovskite QLED fabrication, laying a foundation for their low-cost, large-scale manufacturing and expansion into diversified applications.

The development of high-performance circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters featuring through-space charge-transfer (TSCT) transitions is fascinating yet challenging due to the difficulty in balancing efficiency, dissymmetry factors, and structural diversity. Here, we report the first helical-configuration integrated TSCT-type CP-TADF emitter, which adopts a dual-spiro-locked face-to-face acceptor/donor/acceptor scaffold. This sandwiched design not only enables degenerate energy states via multi-channel TSCT transitions but also incorporates multiple stereogenic centers, resulting in an exceptionally small singlet-triplet energy gap of 0.04 eV, a high reverse intersystem crossing rate of >106 s- 1, and near-unity photoluminescence quantum yields (>93%), accompanied by a benchmark high photoluminescence dissymmetry factor (|gPL|) of 4.4 × 10- 3 among such TSCT-type emitters. When applied as an emitter in organic light-emitting diodes (OLEDs), this molecule achieves a maximum external quantum efficiency (EQEmax) of 27.4% with suppressed efficiency roll-off and strong electroluminescence dissymmetry (|gEL| ≈ 3.2 × 10- 3). When used as a sensitizer for a multiple-resonance TADF emitter, it enables an impressive maximum external quantum efficiency (EQEmax) of 38.4% while maintaining high |gEL| (≈ 3.0 × 10- 3). This work greatly diversifies the structural frameworks of TSCT-type CP-TADF emitter with improved performance.

ABSTRACT Narrowband multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters are pivotal for wide‐color‐gamut displays, yet they often encounter an inherent trade‐off between emission redshift and spectral broadening. In this study, we present a molecular design strategy that incorporates antiaromatic four‐membered rings into a boron‐ and nitrogen‐embedded MR framework to achieve aromaticity localization. This approach enhances the aromaticity localization within the MR skeleton, effectively suppressing vibrational coupling and narrowing the emission spectrum, while simultaneously extending the π‐conjugation to induce a bathochromic shift—thereby counteracting the typical broadening that accompanies redshift. Relative to the DABNA‐1 parent molecule, the designed emitter exhibits a substantially redshifted emission maximum from 460 to 523 nm, along with a narrowed full‐width at half‐maximum (FWHM) from 27 to 16 nm. The corresponding organic light‐emitting diode (OLED) achieves a narrow FWHM of 21.5 nm with CIE coordinates of (0.26, 0.70), a maximum external quantum efficiency (EQE max ) of 36.1%, and a significantly low efficiency roll‐off. Remarkably, the device demonstrates superior operational stability with an LT90 lifetime of 1469 h at an initial luminance of 1000 cd m −2 . This work establishes a novel paradigm in molecular design for realizing long‐wavelength MR‐TADF emitters that concurrently achieve high color purity and excellent electroluminescence performance.

Smart textiles face inherent compromises between functionality and wearability due to rigid electronics and complex circuitry. Here, we introduce a touch-luminescence (TouchLumi) fiber that overcomes this trade-off by enabling chip-free, real-time tactile-visual interaction via electric field confinement. The fiber integrates a conductive core, a high-permittivity poly(vinylidene fluoride) hexafluoropropylene/barium titanate dielectric layer, and a copper ion-doped zinc sulfide electroluminescent sheath. Upon touch or conductor-induced capacitive coupling, dielectric mismatch concentrates the electric field within the emissive layer, driving localized and simultaneous high-brightness emission at a portable 3-volt power without requiring any other external field or support. This synergistic design merges tactile signal detection and visual feedback into a unified closed-loop system. Crucially, TouchLumi fibers are continuously producible with robust washability and textile compatibility, supporting digital embroidery and large-area machine weaving. We demonstrated its applications, including selective pattern illumination via wet-fingertip activation, multipoint responsive interfaces, and optical messaging through a keyboard textile. TouchLumi fiber enables intuitive tactile-visual interaction that unlocks transformative applications in assistive and inclusive communications.

Perovskite quantum dots are promising for near-infrared light-emitting diodes, although they face serious challenges in limited operating device lifetime originating from the complex and disordered surface atomic states. Here, we design and use multifunctional zinc(II) 4-aminobenzenesulfonate to mitigate surface structural disorder in quantum dots, thereby achieving high-performance near-infrared light-emitting diodes. Such an additive, with four functional groups and ions (-NH2, -S-O, -S=O, and Zn2+), and that shows double hydrogen-bonding effects, can strengthen surface atom termination and mitigate surface disorder, enabling an improved photoluminescence quantum yield of more than 90%. The as-fabricated light-emitting diodes demonstrated narrow electroluminescence spectra with a full width at half maximum of 42 nanometers at 789 nanometers, a maximum external quantum efficiency of 23.11% with negligible efficiency roll-off (as small as 3% at 100 milliamperes per square centimeter), a radiance of 155,851 milliwatts per steradian per square meter, and an operating lifetime of 2298 minutes at an initial radiance of 1,000 milliwatts per steradian per square meter (39,000 minutes for 190 milliwatts per steradian per square meter). This work represents a substantial improvement in radiance, efficiency roll-off, and operating stability compared with the best previously reported near-infrared perovskite quantum dot light-emitting diodes.

While intramolecular cyclization effectively modulates photoelectronic properties of multi-resonance (MR)-thermally activated delayed fluorescence (TADF) emitters, simultaneous narrowing full width at half maxima (FWHM) of spectra and accelerating reverse intersystem crossing (RISC) remain a formidable challenge. Here, we introduce a phosphorus-carbon-bridged cyclization in MR skeletons to synergistically suppress high-frequency molecular vibrations via skeleton rigidification and enhance spin-orbital coupling through introducing heavy-atom effects. Implementing this approach, two blue emitters, phenylphosphine oxide-bridged (BCzBN-PO) and phenylphosphine sulfide-bridged (BCzBN-PS), are developed and exhibit emission peaks at 467 and 474 nm with FWHMs of 19 and 18 nm, respectively. Moreover, benefiting from the additional heavy atom effect of sulfur complementing that of phosphorus, BCzBN-PS achieved a kRISC of 8.5 × 105 s-1, nearly 8-fold higher than that of BCzBN-PO (1.1 × 105 s-1). In the non-sensitized device architecture, both emitters exhibited narrowband emission with a FWHM < 30 nm and a maximum external quantum efficiency (EQE) > 20%. Notably, BCzBN-PS, leveraging its higher upconversion rate, demonstrated a superior maximum EQE and lower efficiency roll-off. Furthermore, in the TADF-sensitized device configuration, the organic light-emitting diodes further validated the enhanced upconversion efficiency-evidenced by BCzBN-PS delivering a higher maximum EQE than BCzBN-PO (43.0% vs. 41.2%) and a reduced efficiency roll-off (30.1% vs. 25.9% at 1000 cd m-2). This work establishes a molecular engineering paradigm that balances color purity and exciton utilization efficiency, paving new avenues for high-performance narrowband electroluminescence.

Multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters featuring rapid reverse intersystem crossing (RISC) are highly desirable for efficient triplet harvesting. Conventional heavy‐atom strategies often enhance RISC at the expense of spectral broadening, particularly when heavy atoms are embedded in 8π‐electron six‐membered rings, where aromaticity reversal between Hückel's and Baird's rules induces structural reorganization. Here, we report a design strategy through peripheral fusion of heavy‐atom‐containing five‐membered aromatic rings into a classical multiple‐resonance framework BCzBN. The rigid aromatic 6π‐electron rings maintain planarity in both ground and excited states for small reorganization energy, which effectively suppresses structural relaxation‐induced spectral broadening, while simultaneously enhancing spin–orbit coupling (SOC). The resulting emitters achieve narrowband pure‐green electroluminescence with a 27 nm full‐width at half‐maximum (FWHM) and Commission Internationale de l′Éclairage y ‐coordinate of 0.72, together with a RISC rate >10 6 s − 1 . Optimized organic light‐emitting diode devices show a maximum external quantum efficiency (EQE) of 31.3% with negligible efficiency roll‐off, maintaining EQEs of 31.2% and 25.6% at 1000 and 10 000 cd m − 2 , respectively. This work demonstrates the critical role of π‐electron counting in heavy‐atom integration and provides a general design principle for high‐performance MR‐TADF materials that concurrently achieve narrow emission and fast RISC kinetics.

Metal halide perovskite light-emitting diodes (LEDs) possess high external quantum efficiency (EQE) and color purity, indicating great promise for next-generation panel displays. In state-of-the-art perovskite LEDs, the hole transport layers and perovskite thin films are solution-processed, whereas the electron transport layers are fabricated through vacuum evaporation deposition. The latter method raises concerns about material waste and environmental pollution, as well as prolonged production duration and increased costs, thereby posing challenges for scalable and sustainable manufacturing. Here, we demonstrate a systematic solvent screening strategy for fabricating perovskite LEDs based on all-solution-processed functional layers. We use ethyl acetate to spin-coat the electron transport material onto perovskite thin films, thereby preserving the device's structural integrity. The as-fabricated deep-red perovskite LEDs show a peak EQE of 4.04% and a maximum radiance of 8221 mWsr-1m-2, among the best performances of all-solution-processed perovskite LEDs. Quantitative analysis indicates that, compared to vacuum evaporation deposition, the material costs, processing duration, and equipment expenses have been reduced by 82%, 90%, and 95%, respectively. Our work establishes a promising construction strategy for solution-processed optoelectronic devices with low cost and high performance, thereby bringing them a significant step closer to their further industrialization and commercialization.

Donor-acceptor (D-A) conjugated polymers are believed to be a promising skeleton for efficient thermally activated delayed fluorescence (TADF). However, it still remains a big challenge to determine the synergistic tuning between the singlet-triplet energy gap (ΔEST) and the oscillator strength (f). Aiming at this object, a polymerization site regulation has been proposed by selecting the same tetramethyl-substituted triphenylamine as the donor and thioxanthone-10,10-dioxide as the acceptor to construct D-A based TADF polymers. Such a design can preserve a small ΔEST of 40–60 meV for all polymers so as to realize a distinct TADF due to the methyl-induced steric locking, while their emission maxima remain almost unchanged. Most importantly, ongoing from 2,7-polymerization to 3,6-polymerization, the photoluminescence quantum yield is found to grow considerably from 20.0

Rapid exciton consumption! Exciton dynamics critically govern the efficiency roll-off and operational stability of organic light-emitting diodes (OLEDs) that incorporate thermally activated delayed fluorescence (TADF) emitters, which utilize 100% of excitons without relying on the unsustainable organometallic complexes required by phosphors. Of critical importance in TADF-OLEDs is the reverse intersystem crossing (RISC) process, which represents the rate-limiting step in exciton dynamics for OLEDs as a result of the restricted generation ratio (1:3) of singlet/triplet excitons under electrical excitation. However, achieving a RISC rate (k(RISC)) exceeding 10(7) s(-1) in TADF emitters has thus far rarely been reported and relies predominantly on the involvement of high-lying localized excited states dictated by the El-Sayed rule. This work demonstrates a strategy for pushing k(RISC) beyond 10(7) s(-1) by leveraging a high-lying triplet state whose charge-transfer transition is nearly enantiomeric with that of the singlet state and thereby supplies an additional channel for triplet up-conversion. The resultant OLEDs exhibit minimal efficiency roll-off and superior operational stability. This design strategy establishes a paradigm for developing efficient TADF emitters focusing on "rapid exciton consumption," advancing the pursuit of commercially viable OLED technologies.

Achieving efficient, stable deep-blue organic light-emitting diodes (OLEDs) with high colour purity remains challenging due to the scarcity of emitters combining narrowband emission and high stability. Here we present a multiple-resonance emitter featuring a highly twisted helical configuration with spatially confined frontier molecular orbitals. This emitter decouples radiative transitions from structural distortion while mitigating spectral broadening from carbon-hydrogen bond repulsion and aggregation, exhibiting sharp emission at 460 nm with a full-width at half-maximum of only 12 nm in solution and nearly identical spectra across varying-polarity systems. A unicolour-hybrid-tandem OLED design integrating complementary exciton-harvesting mechanisms to overcome the efficiency-lifetime trade-off is proposed, achieving an external quantum efficiency of 39.7% and a lifetime of 539 h to 90% of 1,000 cd m⁻2 at a chromaticity y coordinate of 0.10. A stacking sequence of emitting units induces a twofold lifetime variation arising from outcoupling efficiency and photoelectric co-ageing differences. This co-engineering strategy advances commercially viable ultrapure-blue OLED displays.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters are research focuses for organic light-emitting diodes (OLEDs) targeting ultra-highdefinition displays. Expanding the multi-resonance plane through multi-boron structures enables emission color tuning and spectral narrowing, which rigid indolocarbazole moieties could further reinforce. However, excessive expansion of conjugated aromatic planes leads to severe aggregation-caused quenching. Herein, we combined the spirofluorene-based multi-resonance skeleton with indolocarbazoles as the bridging unit to construct a double-boron architecture, aiming to utilize the threedimensional spatial rigidity of spirofluorene while suppressing intermolecular interactions in aggregated states. Three isomeric emitters were thereby obtained, with emission maxima at 524–565 nm. All emitters exhibit full widths at half-maximum below 20 nm, with the narrowest being 17 nm, and these emitters maintain narrow-band emission even at a high doping concentration of 6 wt%, where film spectral broadening is limited to within 3 nm. OLEDs based on these emitters display narrow bandwidths of 22–26 nm, a highest maximum EQE of 36.2%, and low efficiency roll-off, corresponding to a high EQE of up to 30.2% even under ultra-high luminance of 5×104 cd m-2. This work confirms the feasibility of spirofluorene-modified multi-boron largeplane multi-resonance emitters and provides a reliable molecular design strategy for narrowband OLEDs.

Narrowband organic light-emitting diodes (OLEDs) are crucial for next-generation ultrahigh-definition displays. However, achieving efficient electroluminescence with a full-width at half-maximum (FWHM) below 10 nm has remained challenging due to the intrinsic vibronic couplings of organic emitters. The pursuit of ultimate narrowband organic luminescent materials is not only a frontier in OLED research but also a decades‑long formidable challenge in materials science. Here we report brand-new narrowband organic emitters featuring a bonding-to-bonding transition. Simultaneous suppression of high-frequency stretching and low-frequency bending vibrations yields a 0–0-dominated transition, thereby reaching the theoretical linewidth limit. An extremely small FWHM of 5.9 nm (27 meV) is achieved in toluene at 298 K, and even 1.7 nm (8 meV) is observed in n-hexane at 77 K. Such a laser-like sharp emission overturns the traditional understanding of organic emitters. The corresponding OLEDs achieve ultrapure green electroluminescence, with record-narrow FWHMs of 8.2–9.3 nm (37–42 meV) in bottom-emitting devices and ultrahigh color purity surpassing the BT.2020 green standard in top-emitting devices. These unprecedented narrowband emitters mark a new milestone in OLED research and provide a transformative materials platform for a range of high-color-purity optical applications.

Indolocarbazole (ICz)-based multi-resonance (MR) emitters have garnered significant attention due to their narrowband emission and synthetic accessibility. However, the structural diversity and accessible spectral range of such systems remain notably constrained, particularly in the yellow region. Notably, introducing a yellow component alongside the conventional red, green, and blue primaries can significantly widen the display color gamut, potentially surpassing the stringent BT.2020 standard. This addition is also key to enabling faithful reproduction of warm, natural hues such as skin tones and sunlight and to reducing the overall power consumption of OLED displays. Herein, we report a one-pot synthetic strategy to directly construct an asymmetric framework, ICz-IAD, which integrates fused five- and six-membered aza-heterocycles. This tailored molecular structure effectively extends pi-conjugation while preserving high rigidity, thereby overcoming the typical trade-off between emission redshift and spectral narrowness. The resulting ICz-IAD emitters represent the first family of yellow-emitting MR materials based on an ICz scaffold, exhibiting photoluminescence peaks at 538-543 nm with full width at half maxima of approximately 24 nm. Remarkably, the corresponding OLED devices achieve record-high performance among fluorescent yellow emitters, delivering a power efficiency of 105.3 lm W-1 and a current efficiency of 94.4 cd A-1 while maintaining excellent color purity.

Ultrahigh-definition displays urgently demand narrowband emitters with ideal Gaussian emission profiles. Multiple resonance (MR) systems are highly competitive yet face a formidable bottleneck: The minimum achievable emission linewidth has become an elusive threshold that cannot be further broken for existing systems. Here, the study proposes a pioneering strategy via intramolecular hydrogen bond construction to break the spectral limit of indolocarbazole (ICz) emitters and develops rotary chiral ICz-fused enantiomeric isomers. This chirality-modified ICz emitter concurrently achieves an emissive peak of 466 nanometers, a full width at half maximum (FWHM) of 56 milli-electron volts, and a suppressed shoulder peak in dilute toluene, impressively achieving the narrowest emission among all reported circularly polarized MR emitters to date. The corresponding electroluminescence device exhibits ultrapure deep-blue emission with a peak wavelength of 469 nanometers and an FWHM of 15 nanometers, as well as high maximum external quantum efficiency of 32.5% with minimal roll-off (20.6% at 10,000 candelas per square meter).

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters are a research focus for organic light-emitting diodes (OLEDs) targeting ultra-high-definition displays. Expanding the multi-resonance plane through multi-boron structures enables emission color tuning and spectral narrowing, which rigid indolocarbazole moieties could further reinforce. However, excessive expansion of conjugated aromatic planes leads to severe aggregation-caused quenching (ACQ). Herein, we combined the spirofluorene-based multi-resonance skeleton with indolocarbazoles as the bridging unit to construct a double-boron architecture, aiming to utilize the three-dimensional spatial rigidity of spirofluorene while suppressing intermolecular interactions in aggregated states. Three isomeric emitters were thereby obtained, with emission maxima at 524-565 nm. All emitters exhibit full widths at half-maximum below 20 nm, with the narrowest being 17 nm, and these emitters maintain narrow-band emission even at a high doping concentration of 6 wt%, where film spectral broadening is limited to within 3 nm. OLEDs based on these emitters display narrow bandwidths of 22-26 nm, the highest maximum EQE of 36.2%, and low efficiency roll-off, corresponding to a high EQE of up to 30.2% even under ultra-high luminance of 5 × 104 cd m-2. This work confirms the feasibility of spirofluorene-modified multi-boron large-plane multi-resonance emitters and provides a reliable molecular design strategy for narrowband OLEDs.

The pursuit of high-efficiency narrowband red emitters for next-generation displays is compounded by the challenge of simultaneously achieving high synthetic yield, narrow spectral line width, and high exciton utilization. Here, we break this trade-off with a high-yield monoborylated multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitter, α-NAICZ-BN, which incorporates key structural motifs from distinct narrowband systems. Our molecular design simultaneously suppresses midfrequency vibrational broadening and enhances reverse intersystem crossing, enabling efficient red emission at 605 nm in solution with a record-narrow 26 nm full-width at half-maximum (fwhm) among monoborylated red MR-TADF emitters. The corresponding organic light-emitting diode achieves narrowband red electroluminescence at 617 nm with CIE coordinates of (0.67, 0.33), while attaining a maximum external quantum efficiency of 29.5% and ultrahigh power efficiency of 53.1 lm W-1 with negligible efficiency roll-off. This work establishes a new design paradigm for high-performance red MR-TADF materials, demonstrating how single-boron molecular frameworks can achieve exceptional color purity and device efficiency simultaneously.

Molecular single crystal materials have demonstrated their elasticity and flexibility recently, highlighting potential applications in flexible electronics. Mechanical strain has significant impact on charge mobility within these crystals. However, the mechanism underlying the dependence of charge mobility on mechanical strain remains elusive. To address this, we combined molecular dynamics, machine learning and Marcus charge transport theory to determine the strain-mobility relationship, in which the machine learning model was applied to accurately predict electronic coupling from molecular structures under the influence of dynamic disorder. Our simulation results of pentacene reveal that a 5% tensile strain along the a-axis enhances charge mobility by 55% along the b-axis, and a 5% tensile strain along the b-axis reduces mobility by 33% in the b-axis. Topological analysis shows that tensile strain along the a-axis reduces intermolecular distance, enhancing the effective charge transport network, while b-axis strain increases these distances, hindering charge transport. Crucially, our simulation indicates that strain along the b-axis significantly enhances the translational and rotational motion of pentacene molecules, thereby broadening the distribution of electronic couplings. The time correlation function of electronic coupling further reveals that strain modifies the temporal characteristics of dynamic disorder, with b-axis strain inducing stronger low-frequency coupling fluctuations which further limit charge transport. Consequently, charge mobility prediction that neglects dynamic disorder can be inaccurate. This study highlights the strain-dependent charge mobility in molecular single crystals and clarifies the boundaries of applicability for fixed electronic coupling models.