Backlight System Research Articles

Efficient and stable CsPbBr3/Cs4PbBr6 composite powders passivated and encapsulated with a novel silicon-based ligand

The metal halide perovskite have garnered significant attention for their exceptional photoelectric properties. However, their inherent instability and the sharp decrease of photoluminescence quantum yield (PLQY) in the solid-state significantly limit their practical applications. Appropriate heterojunction structures or matrix encapsulation can efficiently improve the PLQY and stability of the metal halide perovskite. Herein, we report a new silicon-based ligand hydrolysis condensation encapsulation to synthesize CsPbBr3/Cs4PbBr6/BTESPA-x (CPB–Si-x) composite powders with improved luminescence properties and enhanced thermal stability. With the increase of BTESPA (from 0 to 150 μL), the efficient hydrolysis condensation process occurs on the surface of CsPbBr3/Cs4PbBr6. Finally, the abundant amino-silane groups in BTESPA bind to undercoordinated Pb2+, thereby suppressing the surface defect states and enhancing the PLQY from 34.3 % for CsPbBr3/Cs4PbBr6 (CPB) to 82.1 % for CPB-Si-5. Simultaneously, the thermal stability of CPB-Si-5 exhibits a 13 % improvement over that of CPB after undergoing thermal cycling. Furthermore, tricolor white light-emitting-diode (WLEDs) with high color rendering index were fabricated using on-chip blue LED with bright green-emissive CPB-Si-5 composite powder and red-emissive K2SiF6:Mn4+ phosphor, demonstrating the potential applicability of these powders in WLED backlight systems.

62‐2: High Frame Rate Scanning Backlight System for Privacy Display with Active Retarder

The demand for higher frame rates and resolutions on display panels remains strong as the gaming market has expanded in recent years. To make new use of these display panels, we have developed a privacy display in combination with active retarder. We made a prototype using high frame rate scanning backlight system and achieved the 4% level for the crosstalk ratio.

Integral imaging three-dimensional display system with anisotropic backlight for the elimination of voxel aliasing and separation.

Compared with conventional scattered backlight systems, integral imaging (InIm) display system with collimated backlight can reduce the voxel size, but apparent voxel separation and severe graininess still exist in reconstructed 3D images. In this paper, an InIm 3D display system with anisotropic backlight control of sub-pixels was proposed to resolve both voxel aliasing and voxel separation simultaneously. It consists of an anisotropic backlight unit (ABU), a transmissive liquid crystal panel (LCP), and a lens array. The ABU with specific horizontal and vertical divergence angles was proposed and designed. Within the depth of field, the light rays emitted from sub-pixels are controlled precisely by the ABU to minimize the voxel size as well as stitch adjacent voxels seamlessly, thus improving the 3D image quality effectively. In the experiment, the prototype of our proposed ABU-type InIm system was developed, and the spatial frequency was nearly two times of conventional scattered backlight InIm system. Additionally, the proposed system eliminated the voxel separation which usually occurs in collimated backlight InIm system. As a result, voxels reconstructed by our proposed system were stitched in space without aliasing and separation, thereby greatly enhancing the 3D resolution and image quality.

42‐4: Automotive Liquid Crystal Display Using mini‐LED Backlight Managed by Flexible Local Dimming System

The automobile industry is entering a period of major transformation. The shift to EVs, autonomous driving, connectivity to networks, etc., suggest the transformation. Along with this, care must be taken to provide passengers with various information. Therefore, the role played by displays will continue to grow in the future. In addition, the shift to EVs forces the demand for reduce of power consumption more and more severe. In this paper, we propose a liquid crystal module suitable for in‐vehicle monitors that combines a mini‐LED backlight system and a flexible control algorithm.

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

56.2: A dynamic backlight for a wide‐angle light field display based on supermulti‐view technology

In naked‐eye 3D display, the light field display has been widely concerned because it can provide vivid and natural 3D performance, and light field display technology based on super‐multi‐view (SMV) has also become an important research direction of naked‐eye 3D display. However, insufficient viewing angle is one of the main factors limiting the development and application of light field display technology. In this paper, we propose a wide‐angle‐splicing display method for dynamic backlight system based on the light field display with SMV technology. The experimental results show that the viewing angle is increased by about 50% from the original 60° to more than 90°, and a time‐multiplexed light field display with a 90° wide viewing angle is demonstrated. At the same time, it can provide the viewer with smooth and continuous motion parallax, and clear 3D images can be perceived at the entire range of viewing angle, which greatly improves the viewer's visual experience.

Half-Bridge LLC Series-Resonant Converter With Hybrid Rectifier for LED Signage Backlighting Systems

Large-area LED signage backlighting systems require power supplies to provide constant voltage to multiple LED modules connected in parallel, each with a built-in LED current regulator to maintain a constant output brightness. LED signage backlighting systems can be divided into 12 V and 24 V, which require different power supply specifications. The development of a universal 2-in-1 LED driver will reduce the number of power supply models and avoid incorrect wiring in the field. A new topology of half-bridge LLC series-resonant converter with hybrid rectifier is proposed in this brief, which automatically switches between full-bridge rectifier and half-wave rectifier by LED current detection. The hybrid rectifier switching mode enables an optimized design with two times the output voltage range, thus reducing the switching frequency range and the circulating current of the LLC series-resonant converter. The performance of the 60 W half-bridge LLC series-resonant converter with hybrid rectifier and the conventional half-bridge LLC series-resonant converter is experimentally compared. The results prove that there is a significant improvement in efficiency based on the 24 V output condition.

Study of the electrothermal and MHD instabilities in exploding cylindrical foil liner

An experimental and numerical study of the plasma instabilities in an electrical exploding cylindrical Al liner is reported. The Al liner 3 mm in diameter and 10 μm in thickness is exploded at the Qin-1 facility (450 ns, 400 kA). Various diagnostics, such as multi-frame laser shadowgraphy, an x-ray framing camera, and an x-ray backlighting system are developed. The different imaging systems are sensitive to plasma of different areal densities based on the comparison between the experiments and simulation, which reveal the dynamics of the exploding liner in more detail. The laser shadow images show the low-density plasma (∼1–2 × 10−4 g cm−2) at the edge of the liner, and both the amplitude and wavelength of the plasma instabilities increase over time, which are considered to be magnetohydrodynamic (MHD) instabilities rather than electrothermal instabilities. During the ablation of the liner, quasi-periodic azimuthally correlated striations are directly observed in extreme ultraviolet (EUV) self-emission images. Meanwhile, the vertical filaments, which are electrothermal instabilities for plasma under the condition of ∂η/∂T < 0, are also observed in EUV self-emission images. The x-ray backlighting images of the exploding liner are obtained by placing an X-pinch load on the current-return path to serve as an x-ray point source (∼1 ns, ∼10 μm). The x-ray backlighting results show the behavior of the high-density plasma (∼1.89 × 10−3 g cm−2), which includes the transition from electrothermal to MHD instabilities. Finally, we realized a 2D MHD simulation of the exploding liner under experimental conditions, which shows good agreement with the results of the experimental perturbation.

P‐7.21: The Main Technologies of Large Size 8K LCD Display System

In recent years，BOE has launched many excellent display products and has been adhering to the research of 8K technology, while leading related technologies. In 2021, we launched a new large size smart display terminal system. In this paper, a new hardware system and several key technologies are proposed for large-size 8K display terminals. In this paper, it is focused on introducing the system architecture of the hardware system, the design of the high zones Mini-LED backlight and driver system, the realization of high color gamut display, and the solution and effect of eyesafe about display.

P‐11.1: Design of directional backlight systems for dual view displays

P‐11.1: Design of directional backlight systems for dual view displays

6.1: Autostereoscopic Display with a Multidirectional Backlight System and an Eye tracker

We implement a time-sequential autostereoscopic display with a multidirectional backlight system and an eye tracker. The proposed multidirectional backlight uses Bragg mismatched reconstruction of volume-holographic optical elements. The eye tracker feeds back eye positions, and the system provides directional and time-sequential parallax images. Through this display, viewers could observe vivid three-dimensional images with high resolution, low crosstalk, and smooth motion parallax.

Portable autostereoscopic display based on multi-directional backlight.

A multi-directional backlight autostereoscopic display system with high resolution, low crosstalk, and motion parallax is developed in this paper. The proposed multi-directional backlight system is based on the Bragg mismatched reconstruction of volume holographic optical element (VHOE), and includes a set of light sources which are uniformly arrayed along one direction. Each light source produces its corresponding directional lighting to follow the human eye position detected by an eye tracker. Two scenarios are presented to build the multi-directional backlight system. The prism-type backlight system which guides the incident beam with a prism is relatively simple and easy to implement. The waveguide-type one which employs a transflective film to expand the incident light beam within the waveguide and modulate the intensity of the incident beam, is relatively thin and is applicable to large-area display. Two prototypes are built and the effectiveness of the proposed autostereoscopic display system is verified by the experimental results.

Development of a High-Energy X-ray Backlighting System for Z-pinch Experiments

A backlighting system is developed for Z-pinch experiments that is composed of a pulsed X-ray generator (the backlighter), a scintillator, an optical module, and an intensified charge-coupled device (ICCD). By optimizing the geometrical layout, choosing the appropriate scintillator, and optimizing the parameters of the optical module, the system is successfully designed. The key properties of the system are theoretically calculated based on parameters of the X-rays and the scintillator. Calculation results of sensitivity show that the amount of scintillator fluorescence falls in the linear dynamic range of the ICCD. Spatial resolution is calculated to be 241 µm, which is mainly determined by the geometrical layout and the size of the X-ray focal spot. Temporal resolution is calculated to be 2.3 ns, which is mainly determined by the decay time of the scintillator. Calculation results indicate that the properties of the system meet the requirements of the Z-pinch capsule diagnostics. The system has been fabricated. Performance of the system is tested through static W wire experiments in the laboratory. Experimental results show that 250-µm W wire is clearly seen in the image when X-ray fluence is high, while 100-µm W wire cannot be seen.

Multi-user, high-resolution, high-quality directional backlight autostereoscopic display

Autostereoscopy with multi-user, high-resolution, homogeneous luminance, low crosstalk is realized with a directional backlight system consisting of specially tailored backlight and composite Fresnel lens array. Numerical simulation is applied to obtain the viewing zone distribution, which is found to be in good agreement with experiment. The dense-distribution of the backlight array allows the system to provide well-controlled directional illumination for multi-viewers while keeping high-resolution for each viewer. The experimental challenge for small crosstalk between left- and right-eyes for individual viewer, and minimized crosstalk between different viewers are fulfilled with high-quality optics design to allow the multi-viewers to simultaneously perceive 3D image. The crosstalk is controlled below 5%, and the homogeneity is above 85% while the resolution for each eye is kept at 1920*1080.

Mechanosynthesis strategy towards a high-efficiency CsPbBr3/Cs4PbBr6 perovskite phosphor

All-inorganic perovskites are promising alternatives to organic-inorganic hybrid halide perovskites in the field of optoelectronic materials. Optimizing the luminescent property of CsPbBr3 is very important to promote its application in optoelectronic devices, and thus a facilitative method to prepare a large number of efficient luminous samples is desirable. In this study, we effectively improve the luminous performance of CsPbBr3 powder by a simple mechanosynthesis strategy. The emission intensity of CsPbBr3 powder is improved by ca. 40 times and the PLQY of the powder sample exceeds 40%. It is disclosed that the defects of CsPbBr3 are passivated and the ratio of the non-radiation recombination is reduced. The formed Cs4PbBr6 during grinding has a zero-dimensional perovskite structure that can limit the migration of the carriers between the [PbBr6] octahedrons. Now CsPbBr3 can be used in powder form other than film or quantum dots. A UV-chip LED is fabricated by using the prepared phosphor, and the narrow-band emission property (FWHM is 22 nm) makes it more suitable for application in back-lighting systems.

Wavelength-Tunable and Water-Stable Cesium-Lead-Based All-Bromide Nanocrystal-Polymer Composite Films Using Ultraviolet-Curable Prepolymer as an Anti-Solvent.

All-inorganic metal halide perovskite nanocrystals (IPeNCs) have become one of the most promising luminescent materials for next-generation display and lighting technology owing to their excellent color expression ability. However, research on IPeNCs with stable blue emission is limited. In this paper, we report stable blue emissive all-bromide IPeNCs obtained through a modified ligand-assisted reprecipitation method using an ultraviolet (UV)-curable prepolymer as the anti-solvent at a low temperature. We found that the blue emission originates from quantum-confined CsPbBr3 nanoparticles formed together with the colorless wide-bandgap Cs4PbBr6 nanocrystals. When the temperature of the prepolymer was increased from 0 to 50 °C, CsPbBr3 nanoparticles became larger and more crystalline, thereby altering their emission color from blue to green. The synthesized all-bromide blue-emitting IPeNC solution remained stable for over 1 h. It also remained stable when it was mixed with the green-emitting IPeNC solution. By simply exposing the as-synthesized IPeNC–prepolymer solutions to UV light, we formed water-stable composite films that emitted red, green, blue, and white colors. We believe that this synthetic method can be used to develop color-emitting composite materials that are highly suitable for application as the color conversion films of full-color liquid crystal display backlight systems and lighting applications.

Backlight system using an interleaved Fresnel lens array that attains a uniform luminance and two-dimensional directional light control.

A novel (to the best of our knowledge) Fresnel lens array is proposed to realize a uniform directional backlight with two-dimensional directionality. Autostereoscopic display with the proposed lens array improves image output quality and relieves the viewer's posture restriction without the need for any additional eye aid. In the proposed lens array, tiny prisms composing two adjacent linear Fresnel lenses are interleaved so that the two lenses may be virtually overlapped and work independently. The widths of the elemental prisms vary depending on the distance from the center of each lens. Thus, the light passing through the two lenses is mixed, which results in higher and more uniform luminance intensity. A prototype of an autostereoscopic display based on the time-multiplexed directional backlight method and made with the proposed lens array attained uniform luminance as well as low cross-talk between left-eye and right-eye images.

Aligned polymer dispersed liquid crystal film for light enhancement of quantum dot backlight

Quantum dots (QDs) have been used to make backlight, which provides a superior color gamut, for liquid crystal flat panel displays. In the backlight system, quantum dots, embedded in a polymer film and illuminated by blue light, emit red and green light with narrow bandwidths. There is, however, a problem with the system in that the quantum dots emit light in all directions, and most of the emitted light is in directions with large incident angles and cannot exit the film due to the total internal reflection at the film-air interface and is wasted. We propose to use an aligned polymer dispersed liquid crystal (APDLC) film to reduce the total internal reflection in the QD backlight and thus improve the light efficiency. A regular PDLC film, where the embedded liquid crystal droplets are randomly oriented, exhibits isotropic scattering and is not a good candidate for the enhancement of light efficiency of QD backlight. Through a two-step polymerization, we successfully developed an aligned polymer dispersed liquid crystal (APDLC) film where the liquid crystal droplets are permanently unidirectionally aligned in the film’s normal direction. It exhibits selective scattering: it scatters light with large incident angles but not light with small incident angles. When the APDLC film is laminated on the QD backlight film, a significant enhancement of the light efficiency of the QD backlight is achieved. The APDLC film can also be used to increase the light efficiency of other flat panel displays, such as organic light emitting diode (OLED) display and micro-light emitting diode (MLED) display.

Enhanced performance of GaN-based visible flip-chip mini-LEDs with highly reflective full-angle distributed Bragg reflectors

High-efficiency GaN-based visible flip-chip miniaturized-light emitting diodes (FC mini-LEDs) are desirable for developing white LED-backlit liquid crystal displays. Here, we propose a full-angle Ti3O5/SiO2 distributed Bragg reflector (DBR) for blue and green FC mini-LEDs to enhance the device performance. The proposed full-angle Ti3O5/SiO2 DBR is composed of different single-DBR stacks optimized for central wavelength in blue, green, and red light wavelength regions, resulting in wider reflective bandwidth and less angular dependence. Furthermore, we demonstrate two types of GaN-based FC mini-LEDs with indium-tin oxide (ITO)/DBR and Ag/TiW p-type ohmic contacts. Experimental results exhibit that the reflectivity of full-angle DBR is higher than that of Ag/TiW in the light wavelength range of 420 to 580 nm as the incident angle of light increases from 0° to 60°. As a result, the light output powers (LOPs) of blue and green FC mini-LEDs with ITO/DBR are enhanced by 7.7% and 7.3% in comparison to blue and green FC mini-LEDs with Ag/TiW under an injection current of 10 mA. In addition, compared with FC mini-LED with Ag/TiW, light intensity of FC mini-LED with ITO/DBR is improved in side direction, which is beneficial to mix light in backlight system of liquid crystal displays (LCDs).

Scanning Backlight System for High Frame Rate LCD with IGZO-TFT Technology

Scanning Backlight System for High Frame Rate LCD with IGZO-TFT Technology