Blueprints for Brightness: A Trilogy of Locking, Substitution, and Extension Strategies in Carbonyl–Nitrogen‐Based MR‐TADF Emitters

Organic light-emitting diodes utilizing thermally activated delayed fluorescence sensitizers and multiple-resonance (MR) dopants may simultaneously offer high efficiencies and narrow-band emissions...

Efficient energy levels and lifetimes regulation of excited states for narrowband thermally activated delayed fluorescence

Towards Efficient Blue Delayed-Fluorescence Molecules by Modulating Torsion Angle Between Electron Donor and Acceptor

Elevating Red Emission: Yb3+ Doped CsPbBr1I2 Nanocrystal Glass for Exceptional PLQY and Stability in Wide Color Gamut Backlit Displays

A pure-blue light-emitting material is one of the key components in the preparation of organic light-emitting diode (OLED) displays. Although high-efficiency blue OLEDs have been realized in therma...

Achieving high-luminescence organic light-emitting devices (OLEDs) with narrowband emission and high color purity is important in various optoelectronic fields. Laser displays exhibit outstanding advantages in next-generation display technologies owing to their ultimate visual experience, but this remains a great challenge. Here, we develop a novel OLED based organic single crystals. By strongly coupling the organic exciton state to an optical microcavity, we obtain polariton electroluminescent (EL) emission from the polariton OLEDs (OPLEDs) with high luminance, narrow-band emission, high color purity, high polarization as well as excellent optically pumped polariton laser. Further, we evaluate the potential for electrically pumped polariton laser through theoretical analysis and provide possible solutions. This work provides a powerful strategy with a material–device combination that paves the way for electrically driven organic single-crystal-based polariton luminescent devices and possibly lasers.

Probing the effect of Y3+/Gd3+ on the optical properties of Gd2-xYxTiO5:Eu3+: Insight into local site-luminescence correlation

Metal halide perovskite nanocrystals (NCs) have been established as promising materials for light‐emitting devices (LEDs) due to their interesting optoelectrical properties, including high photoluminescence quantum yield (PLQY) and high color purity with narrow full width at half maximum (FWHM). However, blue perovskite LEDs, with an emission wavelength below 470 nm, require further investigation to improve their performance. Here, it is demonstrated that mixed‐halide CsPb(Cl/Br)3 NCs prepared by ligand exchange with the rigid bidentate structure of adamantane‐1,3‐diamine (ADDA) can be used for blue LEDs. The ligand exchange of CsPb(Cl/Br)3 NCs with ADDA improves PLQY without changing the peak wavelength and FWHM. The LEDs based on ligand exchange NCs with ADDA show an external quantum efficiency (EQE) of 0.49%. Moreover, a quaternary ammonium salt, oleylammonium chloride (OAM‐Cl), is also investigated as an interfacial layer to reduce current density. The LED fabricated with OAM‐Cl reaches an EQE of 1.1% and luminance of 43.2 cd m−2 at the electroluminescence wavelength of 456 nm, representing significantly higher performance compared to that of LEDs without OAM‐Cl layers. Therefore, the ligand exchange of NCs with ADDA and the use of a passivation layer comprising OAM‐Cl facilitate an improvement in the LED performance.

Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

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.

An excellent thermally activated delayed fluorescence (TADF) emitter requires a sophisticated molecular design strategy to incorporate structural features to simultaneously achieve high photoluminescence quantum yield (PLQY) and high horizontal emission dipole ratio (Θ//). This work reports the uses of heteroarenes and dicarbonitrile benzenes to design four new acceptors PymCN, PyoCN, PmmCN, and PmoCN, which are linked to a common donor dimethylacridine (DMAC) for making new TADF emitters. The emission wavelength, ΔEST, krisc, kr, and the resulting PLQY of the target TADF emitters are governed by the combined natures of the heteroaryl bridges (Py vs Pm) and the CN‐substituted patterns (o‐CN vs m‐CN). The photophysical and device characteristics reveal the best acceptor to be PyoCN, which is further coupled with spiroacridine to afford a new emitter SpiroAC‐PyoCN with an enhanced PLQY of 100% compared to that (91%) of the DMAC‐based counterpart DMAC‐PyoCN. Furthermore, linking PyoCN with spiro‐bisacridine (SBAC) gives an A–D–A‐configured TADF emitter SBAC‐PyoCN with both enhanced PLQY (100%) and Θ// (90%). The device employing SBAC‐PyoCN as emitter renders a maximum external quantum efficiency up to 36.1% owing to its unity PLQY and superior light out‐coupling efficiency. This rational molecular design strategy provides a feasible means to achieve an excellent TADF emitter design.

Achieving multicolor organic afterglow materials with narrowband emission and high color purity is important in various optoelectronic fields but remains a great challenge. Here, an efficient strategy is presented to obtain narrowband organic afterglow materials via Förster resonance energy transfer from long-lived phosphorescence donors to narrowband fluorescence acceptors in a polyvinyl alcohol matrix. The resulting materials exhibit narrowband emission with a full width at half maximum (FWHM) as small as 23nm and the longest lifetime of 721.22ms. Meanwhile, by pairing the appropriate donors and acceptors, multicolor and high color purity afterglow ranging from green to red with the maximum photoluminescence quantum yield of 67.1% are achieved. Moreover, given their long luminescence lifetime, high color purity, and flexibility, the potential applications are demonstrated in high-resolution afterglow displays and dynamic and quick information identification in low-light conditions. This work provides a facile approach for developing multicolor and narrowband afterglow materials as well as expands the features of organic afterglow.

The pursuit of next-generation ultrahigh-definition displays has intensified the demand for narrowband emitters with exceptional color purity and high efficiency. Despite the demonstrated superiority of multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters in vacuum-deposited OLEDs, their solution-processing implementation faces significant challenges stemming from inherent molecular rigidity, which compromises solubility, film morphology, and inefficient exciton utilization. Herein, two novel solution-processable, pure-green MR-TADF emitters, DBN-Pym and DBN-PhPym, are reported via an acceptor-bridged engineering strategy that integrates MR cores with electron-withdrawing pyrimidine bridges. Such a design simultaneously enhances the solubility through controlled molecular torsion and precisely modulates the electron distribution via synergistic long- and short-range charge transfer. Consequently, the resulting emitters exhibit narrowband green emission (514/513nm, full width at half maximum, FWHM: 24-30nm) with remarkably high photoluminescence quantum yields (PLQYs) of 86% and 99%, respectively. Solution-processed OLEDs exhibit peak emissions at 526/521nm with Commission Internationale de L'Eclairage (CIE) y coordinates exceeding 0.69. Notably, the DBN-PhPym achieves a record external quantum efficiency (EQE) of 29.0% (maintaining 28.3% at 1000cd m-2), with an FWHM of 34nm, representing state-of-the-art performance for solution-processed MR-TADF devices. This work establishes an effective molecular design strategy for developing efficient narrowband emitters, paving the way for solution-processable ultrahigh-definition displays.

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr3 ) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr3 QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr3 perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr3 QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr3 QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.

All inorganic lead halide perovskite nanocrystals (NCs), CsPbX3 (X=Cl, Br, I), have been attracting increasing attention because of their excellent optical properties, such as tunable emission wavelength, high photoluminescence quantum yield (PLQY), narrow full width at half maximum (fwhm), and high defect tolerance. Therefore, the NCs have great potential application in light-emitting diodes for display. However, the NCs suffer from poor stability due to the hydrolytic degradation and fluorescence quenching in the solid agglomerations state. To improve the photoluminescence (PL) stability of the NCs, the ammonium bromide, alkyl phosphate, microscale Cs4PbX6, and super hydrophobic porous organic polymers (SHOP) were used as frameworks to from the composites with NCs. Specially, the CsPbBr3-super hydrophobic polymers composites not only preserve a high PLQY (60%) and narrow band emission (fwhm~16nm) but also inherit the outstanding water-resistant property of SHOP to protect the NCs from hydrolytic degradation. The PLQY of the composites was maintained at 91% of the initial one after being immersed in water for 31 days. Even after being immersed in water for six months, the composites still retain bright green emission. A white light-emitting diode (WLEDs) device was prepared by combining green-emitting composites and red-emitting K2SiF6:Mn4+ phosphors with a blue LED chip. The device exhibits a high luminous efficiency of 50 lm/W and a wide color gamut (127% of the National Television System Committee and 95% Rec. 2020). This work provides an alternative approach to solve the challenging stability issue of perovskite QDs; therefore, it has a positive implication for their practical application in liquid crystal display backlights.