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Carbon-based emitters (CBEs) offer promising. readily yielding commercially viable light-emitting diodes for display technology due to their abundance, flexibility, and environmental friendliness. However, uncontrolled vibronic coupling in CBEs often results in broad, inferior-color-purity emissions, posing a significant challenge in realizing the Rec. 2020 standard.We review narrow-bandwidth CBEs, including small organic molecules, polymers, and carbon dots, focusing on the relationship between molecular structure and optical properties.Recent frontiers in the optical characteristics of narrow-bandwidth CBEs based on structural design are examined from diverse perspectives, encompassing molecular rigidity, doping of atoms in the molecular skeleton, functional groups, and spatial structure.We conclude with a discussion regarding the key challenges and plausible future prospects in this field.

Thermally activated delayed fluorescent (TADF) and phosphorescent blue organic light‐emitting diodes (OLEDs) have been developed to overcome the relatively low triplet exciton utilization of traditional fluorescent OLEDs. However, broad emission spectra originating from charge transfer process limits the commercial application of such blue OLEDs. Herein, an effective phosphor‐sensitized fluorescent (PSF) OLED device structure was designed. PSF OLED exhibited a maximum blue index (BI) of 508 cd/A/CIEy with CIEy of 0.060, which has been the highest efficiency result reported for PSF deep‐blue OLEDs. Impressively, the sensitized OLEDs maintained blue index of 407 cd/A/CIEy, narrow emission spectra (FWHM = 17 nm) and high color purity (CIEy = 0.046), revealing the attractive technical advantages and commercial application potential.

We are introducing an innovative organic semiconductor electroluminescent device capable of emitting light with unprecedented characteristics: high directionality (divergence angle of 1.1°) and high color purity (full width at half‐maximum of 2.5 nm). This achievement was realized through intricate design techniques aimed at enhancing gain via meticulous recombination zone control, complemented by the reduction of losses through minimizing the overlap of the optical mode with the electrodes. These groundbreaking results mark the world's first demonstration of simultaneously achieving a narrow spectrum and superior directionality in an organic electroluminescent device.

With the increasing performance demand from the display market, it has become ever more important to realize wide color gamut requirement. In this paper, we fabricated a series of pTSF green devices, the optimal devices which exhibit excellent performance in the range of CIEx 0.17‐ 0.22, with the central color point meeting Adobe's green light requirements, showing the advantages in wide color gamut. Additionally, they have comparable performance to existing phosphporescent devices under DCI‐P3 light color, showing the advantages of high performance and high color purity.

We are introducing an innovative organic semiconductor electroluminescent device capable of emitting light with unprecedented characteristics, that is, high directionality with divergence angle of 1.1°and high color purity with the full‐width at half‐maximum of 2.5 nm. This achievement was realized through design techniques aimed at enhancing gain via meticulous recombination zone control and complemented by the reduction of the optical losses. These results demonstrate the simultaneous achievement of a narrow spectrum and high directionality in an organic electroluminescent device. We introduce an innovative organic semiconductor electroluminescent device. This device is capable of emitting light with unprecedented characteristics, that is, high directionality with divergence angle of 1° and high color purity with the full width at half maximum of 2.5 nm. These results demonstrate the simultaneous achievement of a narrow spectrum and high directionality in an organic electroluminescent device.

Thermally activated delayed fluorescent (TADF) and phosphorescent blue organic light‐emitting diodes (OLEDs) have been developed to overcome the relatively low triplet exciton utilization of traditional fluorescent OLEDs. However, broad emission spectra originating from charge transfer process limit the commercial application of such blue OLEDs. Herein, an effective phosphor‐sensitized fluorescent (PSF) OLED device structure was designed. PSF OLED exhibited a maximum blue index (BI) of 508 cd/A/CIEy with CIEy of 0.060, which has been the highest efficiency result reported for PSF deep‐blue OLEDs. A nearly 100% improvement in operational lifetime LT95(L/L0= 95%) was achieved successfully by using lower triplet energy (T1) and deuterated host materials. Impressively, the sensitized OLEDs maintained BI of 407 cd/A/CIEy, narrow emission spectra (FWHM = 17 nm), and high color purity (CIEy = 0.046), revealing the attractive technical advantages and commercial application potential. An effective phosphor‐sensitized fluorescent organic light‐emitting diode (OLED) device structure was elaborately fabricated to achieve a maximum blue index of 508 cd/A/CIEy with CIEy of 0.060, which has been the highest efficiency result reported for PSF deep‐blue OLEDs.

With the increasing performance demand from the display market, it has become ever more important to realize wide color gamut requirement. In this paper, we fabricated a series of pTSF green devices, the optimal devices which exhibit excellent performance in the range of CIEx 0.17‐0.22, with the central color point meeting Adobe's green light requirements, showing the advantages in wide color gamut. Additionally, they have comparable performance to existing phosphporescent devices under DCI‐P3 light color, showing the advantages of High Performance and High Color Purity

Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation. Typical phosphor designs employ UCr4C4-type compounds and designing new narrow-band phosphors with high color purity is a major challenge. Here, we explored a Eu2+-doped Ba5GeO4Br6phosphor, showing a narrow-band blue emission (λem = 436 nm) excitation at the near-ultraviolet light with a full width at half maximum of 30.7 nm and high color purity of 96.6%. In addition, attractive cathodoluminescence characteristics were systematically analyzed by varying filament current (30–70 mA) and accelerating voltage (3–7 eV). Robust anti-degradation behavior and color point stability under continuous electron beam bombardment were confirmed. Given its excellent performance in photoluminescence and cathodoluminescence, application in wide color gamut displays appears promising. Using commercial phosphors β-SiAlON:Eu2+and K2SiF6:Mn4+as green and red light converters respectively, and the title phosphor as the blue light converters, the fabricated w-LED exhibits a wide color gamut of 82% NTSC.

We synthesized reddish-orange luminescent La10W22O81(LWO):Sm3+microphosphors by hydrothermal-assisted solid-state reaction. X-ray diffraction analysis reveals that all the studied phosphors crystallize in an orthorhombic structure in the Pbcnspace group (60). Field emission scanning electron microscopy indicates that the LWO:1.5 mol% Sm3+phosphor displays a smooth-surfaced hexagonal rod-like shape, with a closed shape at both ends, and high-resolution transmission electron microscopy demonstrates a robust crystalline structure. The chemical composition and valence states of the phosphor were investigated using X-ray photoelectron spectroscopy. At 403 nm excitation, LWO:1.5 mol% Sm3+exhibits maximum intensity with the strongest band at 596 nm (4G5/2 → 6H7/2) in the reddish-orange region. The intensity of Sm3+emission decreases beyond 1.5 mol% owing to concentration quenching regulated by dipole–quadrupole interaction between Sm3+ions. The optimized microphosphor LWO:1.5 mol% Sm3+exhibits color coordinates (0.5760, 0.4207), which is close to that of the Amber LED-NSPAR 70 BS (0.570, 0.420), displaying the highest color purity of 99.2% and correlated color temperature of 1694 K. In addition, both breast cancer cells MCF-7 and normal lung fibroblasts WI-38 were tested for toxicity with the optimized microphosphor. It is found that the LWO:1.5 Sm3+microphosphor is extremely toxic to cancer cells, but not to normal cells. Based on these results, LWO:Sm3+microphosphor can serve as a biomedical candidate for the treatment of cancer, as well as a potential multicolor emitting material for w-LEDs.

Cross-linkable hole transport materials (HTMs) are ideal for improving the performance of solution-processed quantum dot light-emitting diodes (QLEDs) and phosphorescent light-emitting diodes (OLEDs). However, previously developed cross-linkable HTMs possessed poor hole transport properties, high cross-linking temperatures, and long curing times. To achieve efficient cross-linkable HTMs with high mobility, low cross-linking temperature, and short curing time, we designed and synthesized a series of low-temperature cross-linkable HTMs comprising dibenzofuran (DBF) and 4-divinyltriphenylamine (TPA) segments for highly efficient solution-processed QLEDs and OLEDs. The introduction of divinyl-functionalized TPA in various positions of the DBF core remarkably affected their chemical, physical, and electrochemical properties. In particular, cross-linked 4-(dibenzo[b,d]furan-3-yl)-N,N-bis(4-vinylphenyl)aniline (3-CDTPA) exhibited a deep highest occupied molecular orbital energy level (5.50 eV), high hole mobility (2.44 × 10–4cm2V–1s–1), low cross-linking temperature (150 °C), and short curing time (30 min). Furthermore, a green QLED with 3-CDTPA as the hole transport layer (HTL) exhibited a notable maximum external quantum efficiency (EQEmax) of 18.59% with a remarkable maximum current efficiency (CEmax) of 78.48 cd A–1. In addition, solution-processed green OLEDs with 3-CDTPA showed excellent device performance with an EQEmaxof 15.61%, a CEmaxof 52.51 cd A–1, and outstanding CIE(x, y) color coordinates of (0.29, 0.61). This is one of the highest reported EQEs and CEs with high color purity for green solution-processed QLEDs and OLEDs using a divinyl-functionalized cross-linked HTM as the HTL. We believe that this study provides a new strategy for designing and synthesizing practical cross-linakable HTMs with enhanced performance for highly efficient solution-processed QLEDs and OLEDs.

Two-dimensional (2D) lead halide perovskites have become a class of promising luminescent materials due to their excitonic nature and excellent environmental stability. However, it seems counterintuitive that the 2D perovskites possess extremely narrow emission, while at the same time they have been reported to reveal strong electron–phonon coupling, which generally leads to significant emission broadening. Here, the main factors affecting the electron–phonon coupling of 2D perovskites are investigated to interpret the observed light emission with full width at half maximum as small as 12.7 nm (∼58 meV) at room temperature (RT). We demonstrate that the electron–phonon coupling in 2D perovskites is structure-dependent, and coupling with the phonon mode in the organic layer rather than the inorganic one plays an important role in the broadening of emission. This scenario is evidenced by temperature-dependent photoluminescence spectroscopy and structural change of 2D perovskites with various bulky organic cations (L-series) and different numbers of inorganic layers (n-series). Our results suggest that the electron–phonon coupling in L-series 2D perovskites could be weak below 250 K, which leads to a small broadening, thus mainly contributing to high color purity at RT. While for the n-series, the increase of inorganic layer number induces a monotonic increase of the line width broadening in the low-temperature region, which reduces the color purity at RT.

With the increasing performance demand from the display market, it has become ever more important to realize wide color gamut and low power consumption. Employing a phosphorescence‐sensitized fluorescence (PSF) mechanism, we introduced a narrow‐spectrum green light‐emitting layer (EML) to the state‐of‐the‐art OLED device structure suitable for mass production and investigate its effect on device performance. Compared with the reference phosphorescent device, the optimal PSF devices have achieved more than 20% efficiency improvement in the range of CIEx 0.17‐ 0.27, showing the advantages of high efficiency and high color purity.

Metasurface‐based color filter have been regarded as good alternatives of conventional color filter causes of their reliability, simple design method, and high resolved pixelization performance. In this study, we designed a novel metasurface‐based color filter with surface plasmons (SPs). The conventional plasmonic color filters (PCFs) have broad transmittance spectra. Consequently, the color purity degrades and this become a fatal issue for practical use. In order to solve the poor wavelength selectivity of the PCFs, we designed a novel PCF integrated with the Fabry‐Perot interferometer (FPI). We added the simple cavity structure over the matching layer of the existing PCF to apply FPI to the PCF. By applying it, the red tail in the long wavelength band of the transmission properties of PCFs were reduced. The color gamut of the suggested filter has increased 2.42 times compared to the conventional PCFs. These improvements are showed the applicability of PCF to various imaging devices.

Lead halide perovskite nanocrystals (PNCs) are emerging as promising light emitters to be actively explored for high color purity and efficient light-emitting diodes. However, the most reported lead halide perovskite nanocrystal light-emitting diodes (PNCLEDs) encountered issues of emission line width broadening and operation voltage elevating caused by the quantum confinement effect. Here, we report a new type of PNCLED using large-size CsPbBr3PNCs overly exceeding the Bohr exciton diameter, achieving ultranarrow emission line width and rapid brightness rise around the turn-on voltage. We adopt calcium-tributylphosphine oxide hybrid ligand passivation to produce highly dispersed large-size colloidal CsPbBr3PNCs with a weak size confinement effect and also high photoluminescence quantum yield (∼85%). Utilizing these large-size PNCs as emitters, we manifest that the detrimental effects caused by the quantum confinement effect can be avoided in the device, thereby realizing the highest color purity in green PNCLED, with a narrow full width at half-maximum of 16.4 nm and a high corrected maximum external quantum efficiency of 17.85%. Moreover, the operation half-life time of the large-size PNCLED is 5-fold of that based on smaller-size PNCs. Our work provides a new avenue for improving the performance of PNCLEDs based on unconventional large-size effects.

Samarium (Sm)-doped Ca12Al14O33(CAO) phosphors were synthesized using solid-state reaction method. Crystal structure of Sm3+-doped CAO was investigated using X-ray diffraction and Raman spectroscopy analysis. Raman active peaks at 320 cm−1, 512 cm−1and 754 cm−1and 773 cm−1were attributed to Ca–O, vibration between Al–O–Al, and ν3 mode of AlO45−groups, respectively. The optical band-gap for pure and Sm3+ion-doped CAO was calculated to be 4.55 eV and 4.50 eV, respectively. Field emission scanning electron microscope (FESEM) image of synthesized phosphors exhibited agglomerated coin-like structure spread with voids. Luminescence properties were analyzed by photoluminescence (PL) spectra. The emission of reddish-orange light due to transition of 4G5/2- 6H7/2was observed, which was confirmed by the Commission Internationale de l’Eclairage (CIE) chromatic coordinate graph. The maximum intensity of orange-red light was observed in 0.5% Sm3+-doped CAO, and the calculated color purity was 95.2%.

Development of multicolor-emitting upconversion nanoparticles (UCNPs) is of significant importance for applications in optical encoding, anti-counterfeiting, display, and bioimaging. However, realizing the orthogonal three-primary color (TPC) upconversion luminescence in a single nanoparticle remains a huge challenge. Herein, we have rationally designed core–multishell-structured NaYF4UCNPs through regulating the dopant concentration, composition of luminescent layers, and shell position and thickness, which are capable of emitting red, green, and blue luminescence with high color purity in response to ternary near-infrared quadrature excitations (1560/808/980 nm). Moreover, their high color purity is well retained with varying excitation power densities. This orthogonal TPC emissions property of such UCNPs endows them with great promise in the field of security. As a proof-of-concept, we have demonstrated the feasibility of combining such UCNPs with MnO2nanosheets for information encryption and decryption. This work not only offers a new way to achieve TPC upconversion luminescence at a single nanoparticle level but also broadens the scope of application for security protection.

Trivalent europium-based monochromatic red light-emitting phosphors are an essential component to realize high-performance smart lighting devices; however, the concentration and thermal quenching restrict their usage. Here, we report a series of efficient Eu3+-substituted Li3Y3BaSr(MoO4)8red-emitting phosphors based on a stratified scheelite structure with negligible concentration and thermal quenching. All of the host and phosphor compositions crystallize in monoclinic crystal structure (space group C2/c). All of the phosphor compositions produce narrow-band red emission (FWHM ∼6 nm), which is highly apparent to the human eyes, and lead to exceptional chromatic saturation of the red spectral window. Concurrently, detailed investigations were carried out to comprehend the concentration and thermal quenching mechanism. Absolute quantum yields as high as 88.5% were obtained for Li3Y0.3Eu2.7BaSr(MoO4)8phosphor with virtuous thermal stability (at 400 K, retaining 87% of its emission intensity). The light-emitting diodes were constructed by coupling Li3BaSrY0.3Eu2.7(MoO4)8red phosphor with a near-UV LED chip (395 nm) operated at 20 mA forward bias, and the hybrid white LED (an organic yellow dye + red Li3Y3BaSr(MoO4)8:Eu3+phosphor integrated with an NUV LED chip) showed a low CCT (6645 K), high CRI (83) values, and CIE values of x= 0.303; y= 0.368, which indicated that the synthesized phosphors can be a suitable red component for white LEDs. In addition, we have systematically investigated the Sm3+and Sm3+, Eu3+activation in Li3Y3BaSr(MoO4)8to display the latent use of the system in plant growth applications and establish that the phosphor exhibits orange red emission with an intense deep-red emission (645 nm (4G5/2→ 6H9/2)). The phytochrome (Pr) absorption spectrum well matched the fabricated deep-red LED (by integrating a NUV LED + Li3Y3BaSr(MoO4)8:Sm3+and Eu3+phosphor) spectral lines.

This paper reports the highly efficient red, green and blue cadmium‐free quantum dots and light‐emitting diodes (QD‐LED). The red and green cadmium‐free QDs with well optimized structure exhibits high color purity. These new QDs have great potential to be used in next generation QD‐LED display with wide color gamut.

The key factors determining the emission bandwidth of thermally activated delayed fluorescence (TADF) are investigated by combining computational and experimental approaches. To achieve high internal quantum efficiencies in a metal-free organic light-emitting diode via TADF, the first triplet (T1) to first singlet (S1) reverse intersystem crossing is promoted by configuring molecules in an electron donor–acceptor (D-A) alternation with a large dihedral angle, which results in a small energy gap (ΔEST) between S1and T1levels. This allows for effective non-radiative up-conversion of triplet excitons to singlet excitons that fluoresce. However, this traditional molecular design of TADF results in broad emission spectral bands (full-width at half-maximum = 70–100 nm). Despite reports suggesting that suppressing the D-A dihedral rotation narrows the emission band, the origin of emission broadening remains elusive. Indeed, our results suggest that the intrinsic TADF emission bandwidth is primarily determined by the charge transfer character of the molecule, rather than its propensity for rotational motion, which offers a renewed perspective on the rational molecular design of organic emitters exhibiting sharp emission spectra.

Thermally activated delayed fluorescence (TADF) sensitization of fluorescence is a promising strategy to improve the color purity and operational lifetime of conventional TADF organic light-emitting diodes (OLEDs). Here, we propose a new design strategy for TADF-sensitized fluorescence based on acrylic polymers with a pendant energy-harvesting host, a TADF sensitizer, and fluorescent emitter monomers. Fluorescent emitters were rationally designed from a series of homologous polycyclic aromatic amines, resulting in efficient and color-pure polymeric fluorophores capable of harvesting both singlet and triplet excitons. Macromolecular analogues of blue, green, and yellow fourth-generation OLED emissive layers were prepared in a facile manner by Cu(0) reversible deactivation radical polymerization, with emission quantum yields up to 0.83 in air and narrow emission bands with full width at half-maximum as low as 57 nm. White-light emission can easily be achieved by enforcing incomplete energy transfer between a deep blue TADF sensitizer and yellow fluorophore to yield a single white-emissive polymer with CIE coordinates (0.33, 0.39) and quantum yield 0.77. Energy transfer to the fluorescent emitters occurs at rates of 1–4 × 108s–1, significantly faster than deactivation caused by internal conversion or intersystem crossing. Rapid energy transfer facilitates high triplet exciton utilization and efficient sensitized emission, even when TADF emitters with a low quantum yield are used as photosensitizers. Our results indicate that a broad library of untapped polymers exhibiting efficient TADF-sensitized fluorescence should be readily accessible from known TADF materials, including many monomers previously thought unsuitable for use in OLEDs.

The class of organic–inorganic lead halides with perovskite crystal structures has recently emerged as promising materials for a variety of practical optoelectronic applications. In particular, hybrid halide perovskite quantum dots possess excellent intrinsic optoelectronic properties such as high color purity (full width at half-maximum of 24.59 nm) and photoluminescence quantum yields (92.7%). In this work, we demonstrate the use of perovskite quantum dot materials as an emissive layer of hybrid light-emitting transistors. To investigate the working mechanism of perovskite quantum dots in light-emitting transistors, we investigated the electrical and optical characteristics under both p-channel and n-channel operation. Using these materials, we have achieved perovskite quantum dot light-emitting transistors with high electron mobilities of up to 12.06 cm2·V–1s–1, high brightness of up to 1.41 × 104cd m–2, and enhanced external quantum efficiencies of up to 1.79% operating at a source–drain potential of 40 V.

In this paper, we have developed a scheme to make small size QD (quantum dot) display come true. We will show the structure and principle of QD display in this paper. It is different from QD enhancement film which is used in backlight, our work focus on developing QD color filter. Compared with traditional LCD, the brightness and color purity of QD‐LCD have been greatly improved. In our development projects, the QD Color filter is realized through the lithography process and we got wide color gamut up to 99.2%BT2020 (equal to 132.86%NTSC) in Cd based QD, and 93.6%BT2020 (equal to 125.35%NTSC) in Cd‐free QD. In this paper we focused on the explaining architectural principles used during design and implementation.

An optical encapsulation structure has been proposed to realize high external quantum efficiency (EQE) and color purity in flexible bottom‐emission organic light‐emitting diodes (OLEDs). It was designed based on the Fabry‐Perot Interferometer (FPI) using optical simulation. The structure showed three sharp peaks in red, green and blue wavelength bands, respectively.

In this paper, we got wide color gamut of quantum dot (QD) films by optimizing the spectra width and optical density (OD) of quantum dots. The specific methods to achieve the following: QD R: one layer of color filter R film was coated below the QD R layer. QD G: one layer of yellow‐green film was coated below the QD G film. By a structure optimal design, we got wide color gamut up to 99.2% BT2020 (equal to 132.86% NTSC) in Cd‐based QD and 93.6% BT2020 (equal to 125.35% NTSC) in Cd‐free QD. Furthermore, the gamut of QD display will continue to be improved by continuous refining the structure of QD display. The figures describe a scheme that the quantum dot (QD) display relies on a multi‐layer design to achieve high purity. The main idea is to place a cut layer below the QD layer to absorb excess light. All the work focuses on the development of efficient cut layers and highly feasible structure.

The creation of white and multicoloured 3D-printed objects with high color fidelity via powder sintering processes is currently limited by discolouration from thermal sensitizers used in the printing process. Here, we circumvent this problem by using switchable, photochromic tungsten oxide nanoparticles, which are colorless even at high concentrations. Upon ultraviolet illumination, the tungsten oxide nanoparticles can be reversibly activated, making them highly absorbing in the infrared. Their strong infrared absorption upon activation renders them efficient photothermal sensitizers that can act as fusing agents for polymer powders in sintering-based 3D printing. The WO3nanoparticles show fast activation times, and when mixed with polyamide powders, they exhibit a heating-to-color-change ratio greatly exceeding other sensitizers in the literature. Upon mixing with colored inks, powders containing WO3display identical coloration to a pristine powder. This demonstrates the potential of WO3,and photochromic nanoparticles in general as a new class of material for advanced manufacturing.

Structural colors with high color purity and low fabrication cost are highly desired in a wide variety of applications including displays, light emitting diodes, decorations, and optical detections. Here, we demonstrate a semitransparent pentalayer structure for creating angle-insensitive, high-purity reflective colors that exploit a higher-order cavity resonance. Moreover, the designed structure in a symmetric configuration presents bright and saturated colors from both directions with a high efficiency up to 85% and a high angular tolerance up to ±60°. The described scheme involves one deposition run, thereby providing a significant step toward large-area applications in various areas.