Display Backlight Research Articles

Research Progress on Quantum Dot-Embedded Polymer Films and Plates for LCD Backlight Display.

Quantum dot-polymer composites have the advantages of high luminescent quantum yield (PLQY), narrow emission half-peak full width (FWHM), and tunable emission spectra, and have broad application prospects in display and lighting fields. Research on quantum dots embedded in polymer films and plates has made great progress in both synthesis technology and optical properties. However, due to the shortcomings of quantum dots, such as cadmium selenide (CdSe), indium phosphide (InP), lead halide perovskite (LHP), poor water, oxygen, and light stability, and incapacity for large-scale synthesis, their practical application is still restricted. Various polymers, such as methyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene (PS), polyvinylidene fluoride (PVDF), polypropylene (PP), etc., are widely used in packaging quantum dot materials because of their high plasticity, simple curing, high chemical stability, and good compatibility with quantum dot materials. This paper focuses on the application and development of quantum dot-polymer materials in the field of backlight displays, summarizes and expounds the synthesis strategies, advantages, and disadvantages of different quantum dot-polymer materials, provides inspiration for the optimization of quantum dot-polymer materials, and promotes their application in the field of wide-color-gamut backlight display.

Engineering Green- to Blue-Emitting CsPbBr3 Quantum Dots in Nanozeolite with High Stability for Backlight Display Application.

The performance of blue devices utilizing perovskite quantum dots (PQDs) has lagged remarkably behind that of green light-emitting diodes because of low luminescence quantum yields and poor spectral stability. Here, benefiting from the rapid and short diffusion paths within the nanosized silicalite-1 (N-Si-1) zeolite (∼40 nm) channels, CsPbBr3 PQDs encapsulated within N-Si-1 show a high dispersion with an ultrasmall particle size of ∼2.38 nm and a blue emission of 474 nm with a high photoluminescence quantum yield (PLQY) of 44.4%. Subsequently, the surface hydrophobization of CsPbBr3-N-Si-1 using octadecyltrimethoxysilane (ODTMS) enables ultrastable blue luminescence. A white-light-emitting diode (WLED) device with CIE color coordinates (0.31, 0.28) was constructed by combining CsPbBr3-M (blue), CsPbBr3-N-Si-1 (green), and KSF:Mn4+ phosphor (red) on a 365 nm chip. This work introduces a feasible strategy to modulate the emission of CsPbBr3 PQDs through a strong confinement effect within a hydrophobic nanozeolite matrix, offering promising applications in backlight displays.

High Efficiency and Narrow-Band Green Emission in Eu2+ and Mn2+ Co-Doped Na2MgAl10O17 Phosphor for Backlight Display Application.

Wide color gamut display has become a new generation of display technology because of its good color saturation. However, the low quantum efficiency and wide half peak width of narrow-band green phosphors are still the main barriers in their development and application. This work addresses these challenges by using Mn2+ as the luminescent center and constructing efficient Eu2+ → Mn2+ energy transfer in Na2MgAl10O17 (NMAO) matrix. The NMAO:0.15Eu2+, 0.30Mn2+ phosphor presents a single-band emission peaking at 513 nm with a full width at half maximum (FWHM) of only 33 nm under the excitation of 365 nm LED chip. In addition, under the excitation wavelength of 365 nm, the energy transfer efficiency reaches 74%. Compared with the NMAO:0.30Mn2+, the intensity of the NMAO:0.15Eu2+, 0.30Mn2+ increases by 5.5 times and the internal quantum efficiency is up to 61.82%. A white LED device with the CIE coordinates of (0.2871, 0.3472) and a color gamut area of 94% NTSC has been assembled successfully by combining 365 nm LED chips with NMAO:0.15Eu2+, 0.30Mn2+, BaMgAl10O17:Eu2+, and K2SiF6:Mn4+ as green, blue, and red component. This work enriches the relevant content of Mn2+-doped phosphors and provides a constructive insight into improving luminescent performance through energy transfer.

Blue light irradiation-stirred washing high luminescence and highly stable CsPbBrI2 quantum dots modified with CaO for backlight display

Blue light irradiation-stirred washing high luminescence and highly stable CsPbBrI2 quantum dots modified with CaO for backlight display

Mn2+ doped aluminum-rich spinel transparent ceramic phosphor with higher performance for wide color-gamut backlight display

Mn2+ doped aluminum-rich spinel transparent ceramic phosphor with higher performance for wide color-gamut backlight display

Zinc-halide/phenylbutyrate co-passivation of CsPbX3 nanocrystals toward efficient and robust luminescence

Cesium lead halide perovskite nanocrystals (IPNCs) exhibit excellent optoelectronic properties but are susceptible to degradation in practical environments due to their ionic surface and unstable ligand capping. Here, we propose a post-synthesis surface passivation strategy for CsPbX3 (X=Br, I) IPNCs by employing combined zinc halide and zinc phenylbutyrate (Zn(PA)2) as surface ligands. ZnBr2 fills surface halide vacancies on IPNCs, resulting in high photoluminescence efficiency, whereas Zn(PA)2 stabilizes IPNCs by substituting surface ammonium ligands. Additionally, the -PA capping endows IPNCs with high solubility in polystyrene (PS), enabling the direct fabrication of highly efficient and uniform IPNCs-PS color conversion films through in situ polymerization of the IPNC-styrene solution. The resulting IPNCs-PS films displayed significantly enhanced stability, retaining excellent PL persistence after 1000h of photoaging. This novel ligand and modification method presents a promising strategy for improving the efficiency and stability of IPNCs, facilitating their potential applications in display backlight and other optoelectronic applications.

Tunable Narrowband to Wideband emission of Mn2+, Eu2+ Co-doped GdMgAl11O19 for multifunctional applications

Tunable Narrowband to Wideband emission of Mn2+, Eu2+ Co-doped GdMgAl11O19 for multifunctional applications

Controllable morphology, excellent stability and non-equivalent doping-induced optical properties of Mn4+-activated K2NaScF6 red phosphor for high-quality warm WLED

Controllable morphology, excellent stability and non-equivalent doping-induced optical properties of Mn4+-activated K2NaScF6 red phosphor for high-quality warm WLED

Design and fabrication of a porous prism film for display backlight applications

This study demonstrates a fabrication method of a porous brightness enhancement film (pBEF) that offers brightness enhancement, light diffusion, color shift reduction, and improved thermal stability. During the ultraviolet imprinting and solvent evaporation processes, the nano/submicron-sized air pores are generated within the polymer prism structure, and micropatterns spontaneously form on the prism surface. The inner pores ranging from 30 to 450 nm can effectively scatter light to mitigate color shift, which is caused by multiple internal reflections within the prism structure. The micropatterns have multiple rings formed one around another with 5–15-µm diameter on the prism surface improve visual quality. Moreover, the obtained functions are achieved in a single film solution, obviating the need for using multiple materials, and the fabrication process is relatively simple and fast as it is conducted under ambient conditions. When the pBEF is integrated into a liquid-crystal display backlight, it provides the brightness enhancement performance and comparable viewing angle distribution of a regular BEF combined with an additional diffuser (two films) and increases brightness by ∼8% compared to a bead prism (particle-based BEF). Additionally, it reduces the redshift (Δxy) from 0.1605 to 0.1415. Furthermore, the pBEF exhibits a lower coefficient of thermal expansion than the regular BEF.

Aluminum Carboxylate Modification Enabled Efficient and Stable Perovskite-Polystyrene Thin Films for Light-Emitting Applications.

Lead halide perovskite nanocrystals (PNCs) have demonstrated great potential in emerging display technologies. However, the practical application of PNCs is hindered by the inherent instability of their ionic surface. Here, we proposed a surface modification approach to enhance the stability of CsPbBr3 PNCs by postsynthetic treatment with aluminum phenylbutyrate (Al(PA)3). Our study reveals that Al(PA)3 displaces ammonium ligands and binds tightly on surface halide, providing excellent air and moisture resistance while preserving a high quantum efficiency of 81.6%. The modified PNCs maintain a constant photoluminescence intensity under continuous UV light illumination for 500 h. Additionally, the Al(PA)3 ligand is compatible with styrene, enabling homogeneous dispersion of PNCs in polystyrene matrices to form bright and uniform PNC-PS thin films. We demonstrated the application of the composite films for display backlighting, which exhibits a wide color gamut of 125% NTSC. The result highlights the potential of AlPA-modified PNCs in light-emitting and other optoelectronic devices.

Synthesis and luminescence properties of a novel narrow band green-emitting Na2MgAl10O17:Mn2+ phosphor for backlight display

Synthesis and luminescence properties of a novel narrow band green-emitting Na2MgAl10O17:Mn2+ phosphor for backlight display

Triple passivation strategy for ultra-stable luminous CsPbBr3 NCs-Acrylate based films as backlight display

Triple passivation strategy for ultra-stable luminous CsPbBr3 NCs-Acrylate based films as backlight display

A Robust Texture-Less Gray-Scale Surface Matching Method Applied to a Liquid Crystal Display TV Diffuser Plate Assembly System

In most liquid crystal display (LCD) backlight modules (BLMs), diffuser plates (DPs) play the essential role in blurring the backlight. A common BLM consists of multiple superimposed optical films. In a vision-based automated assembly system, to ensure sufficient accuracy, each of the multiple cameras usually shoots a local corner of the DP and jointly estimates the target pose, guiding the robot to assemble the DP on the BLM. In general, DPs are typical of texture-less objects with simple shapes. Due to the image background of superimposed multilayer optical films, the robustness of the most common detection methods must be improved to meet industrial needs. To solve the above problem, a texture-less surface matching method based on gray-scale images was proposed. An augmented and normalized gray-scale vector represents the texture-less gray-scale surface in a low-dimensional space. The cosine distance is then used to calculate the similarity between the template and matching vectors, combined with shape-based matching (SBM); the proposed method can obtain high robustness when detecting DPs. An image database from actual production lines was used in the experiment. In comparative tests with the NCC, SBM, YOLOv5s, and YOLOv5x methods, our proposed method had the best precision at all confidence thresholds. Although recall was slightly inferior to SBM, the comprehensive evaluation F1-Score reached 0.826, significantly outperforming the other methods. Regarding localizing accuracy, our algorithm also performed best, reaching 5.7 pixels. Although the time consumption of a single prediction is about 0.6 s, it can still meet industrial needs. These experimental results show that the proposed method has high robustness in detecting DPs and is especially suitable for vision-based automatic assembly tasks in BLM.

Polarized emission of Cs3Cu2I5 nanowires embedded in nanopores of an anodic aluminum oxide template.

Due to the intrinsic polarized emission property, polarized emissive materials with anisotropic nanostructures are expected to be potential substitutes for polarizers. Herein, by the template-assisted strategy, well-aligned lead-free metal halide Cs3Cu2I5 nanowire (NW) arrays are fabricated by evaporating the precursor ink in the anodic aluminum oxide (AAO) for polarized emission. The Cs3Cu2I5/AAO composite film emits highly polarized light with a degree of polarization (DOP) of 0.50. Furthermore, by changing the molar ratio of CsI/CuI, the stability of Cs3Cu2I5 precursor inks is improved. Finally, an ultraviolet (UV) light-emitting diode (LED) is adopted to pump the composite film to achieve a blue LED device. The reported Cs3Cu2I5/AAO composite film with highly polarized light emissions will have great potential for polarized emission applications such as liquid crystal display backlights, waveguides, and lasers.

Solution-grown millimeter-scale Mn-doped CsPbBr3/Cs4PbBr6 crystals with enhanced photoluminescence and stability for light-emitting applications.

Metal halide perovskites are particularly emerging for optoelectronic applications in light-emitting diodes, photodetectors, and solar cells due to their flourishing photophysical properties. However, the poor stability of three-dimensional (3D) lead halide perovskite nanocrystals (NCs) significantly hampers their optoelectronics and photovoltaics applications. Embedding 3D perovskites into zero-dimensional (0D) perovskite crystals and doping ions of appropriate elements into host lattices provide effective approaches to improve the stability and optical-electronic performance. In this study, millimeter-scale Mn-doped and undoped CsPbBr3/Cs4PbBr6 perovskite crystals were successfully fabricated by a one-step slow cooling method. We systematically investigated the effects of Mn2+ ion doping on the PL performance and stability of CsPbBr3/Cs4PbBr6 crystals. Compared with undoped crystals, the existence of Mn2+ ions not only blue-shifted the PL peak but also improved the luminescence performance and stability of the prepared millimeter-sized crystals. Moreover, doping Mn2+ ions can increase the proportion of radiative recombination at low temperature, which may be because Mn2+ ions can effectively accelerate the decay of a dark exciton by the magnetic mixing of bright and dark excitons. In addition, green LED devices with high efficiency packaged as-grown crystals are explored, which promises further application in display backlights.

Anti-thermal Quenching in Blue Phosphor Ba3YAl2O7.5: Tm3+

Blue-emitting phosphors are essential components of the color plasma display panel (PDP), white light-emitting diodes (W-LEDs), and liquid crystal display (LCD) backlights. However, the thermal quenching effect of the phosphor is a serious problem in practice. In this work, a new kind of blue phosphor Ba3YAl2O7.5: xTm3+ was prepared and the luminescent characteristic and thermal stability were studied. Under 358 nm excitation, the phosphors produced a blue emission peak centered at 461 nm, which is due to the transition of Tm3+ from level 1D2 to 3F4. Moreover, the optimal sample Ba3YAl2O7.5: 0.03Tm3+ shows an anti-thermal quenching effect in which the emission intensity at 210 °C rises to 120 % of that at 30 °C , attributable to the presence of oxygen vacancy defects. The result indicates that the Ba3YAl2O7.5: Tm3+ with excellent thermal stability is a promising blue phosphor for lighting and display fields.

All-Inorganic Green Synthesis of Small-Sized and Efficient K2SiF6:Mn4+ Phosphor for Mini-LED Displays.

High-resolution liquid crystal display (LCD) backlight requires a color conversion layer featuring micrometer light-emitting particles and a uniform morphology. The widely used commercial red-emitting K2SiF6:Mn4+ phosphor, showing promise as a light-conversion candidate, faces limitations due to its toxic synthesis process, large particle size, and poor moisture resistance. We successfully demonstrated an efficient substitution of the highly toxic HF/TEOS/KHF2 solvent system with a commonly used HCl/SiO2/KF solvent system to synthesize the small-sized K2SiF6:Mn4+ phosphor. Additionally, surface passivation was performed to enhance the luminescence intensity and resistance to moisture, denoted as K2SiF6:Mn4+@CaF2. Accordingly, the K2SiF6:Mn4+@CaF2 phosphor presents a high luminescence efficiency (99.87%/32.84% IQE/EQE) with an average particle size of ∼2.67 μm. Notably, after exposure to 85% humidity and 85 °C temperature for 3 h, the luminescence intensity remains at 47.4% for K2SiF6:Mn4+@CaF2, while 21.2% for pristine K2SiF6:Mn4+, and only 3.5% for K2SiF6:Mn4+ synthesized by TEOS. These advancements hold great potential for improving high-resolution LCD backlighting, particularly for displays with micron-level pixels, opening up new possibilities for enhanced display technology.

Scalable Synthesis of Lead‐Free Tetramethylammonium Manganese Halides for Highly Efficient Backlight Displays

AbstractLead‐free halides have emerged as clean candidates for lighting and display applications because of their superior optoelectronic properties and environmental friendliness. As for the commercialization, the simple synthetic process, scaled production, low‐cost, and excellent performance are the upmost factors. In this work, lead‐free tetramethylammonium manganese halides are quantitatively synthesized using a mechanochemical approach, in which [(CH3)4N]2MnCl4 powders show green emission with a photoluminescence quantum yield (PLQY) of 21% and (CH3)4NMnCl3 powders possess red emission with a PLQY of 51%, arising from the intrinsic 4T1(4G) → 6A1(6S) d‐d transition of Mn2+. To further boost the green emission efficiency, the composition engineering strategies by Br/Cl substitution and excess organic halide compensation are developed, achieving a high PLQY of 98% for the obtained [(CH3)4N]2MnBr4 powders. Furthermore, white light emitting diode (WLED) devices are fabricated by combining green [(CH3)4N]2MnBr4 powders with red (CH3)4NMnCl3 powders or single crystals, which exhibit a high luminous efficacy (98.06 or 142.40 lm W−1), wide color gamut (over 100 % of NTSC in CIE 1931), and good operating stability (maintained above 80% efficiency after 176 h). This work suggests ball‐milling as a mass synthesis method for metal halides and provides a new Mn2+‐based phosphor for white LEDs in backlight display applications.

Two-Step Performance Optimization of CsPbBr3 Perovskite Nanocrystals for Wide Color Gamut Displays

Owing to their composition-tunable and narrow emissions and high photoluminescence quantum yield (PLQY), inorganic halide perovskite quantum dots (IPQDs) are a promising option for wide color gamut displays. However, their practical applications have been limited by their lattice structure instability and surface defect states. Herein, CsPbBr3:KBF4@SiO2 with improved stability and optical properties is successfully synthesized with a two-step optimization of fluorine (F) anion doping and SiO2 in situ coating. Compared with bromide (Br), higher electronegativity and a smaller radius of F lead to stronger binding energy with Pb2+. Also, F anions can occupy surface Br vacancies. Then, benefiting from the acidic environment provided by BF4− hydrolysis, tetraethyl orthosilicate (TEOS) can be more easily hydrolyzed on the CsPbBr3:KBF4 surface to generate SiO2 coating, thus further passivating lattice defects and improving environmental stability. Importantly, the PLQY of CsPbBr3:KBF4@SiO2 achieves 85%, and the stability has been greatly improved compared with pure CsPbBr3. Finally, CsPbBr3:KBF4@SiO2/PDMS, CsPbI3/PDMS, and CsPbCl3/PDMS composites with narrow emissions are applied to replace traditional phosphors as color converters for direct-view light-emitting diode (LED) displays or liquid crystal display (LCD) backlights. The color gamut reaches 118.22% under the NTSC standard. Concerning the display field, it suggests likely applications in the future.

Tunable color and efficient energy transfer of KBaBP2O8:Ce3+, Tb3+ phosphors with low thermal quenching

Tunable color and efficient energy transfer of KBaBP2O8:Ce3+, Tb3+ phosphors with low thermal quenching