High-Uniformity Planar Mini-Chip-Scale Packaged LEDs with Quantum Dot Converter for White Light Source

Zero-optical-distance mini-LED backlight with light-guiding microstructure lens for extra-thin, large-area notebook LCDs

Mini-light-emitting diode (Mini-LED) backlight units (BLUs) in combination with high dynamic range technology can reduce energy and ensure high contrast and luminance. However, the number of LEDs used in mini-LED BLUs is considerably larger than the number of partitions in local dimming, resulting in low cost effectiveness. We proposed a design combining edge-light mini-LEDs and light-guiding microstructure lenses to reduce the number of light sources required in displays considerably. A 16-inch prototype was produced for experiments. The length, width, and thickness of the liquid crystal display module were 351.87, 225.75, and 1.709 mm, respectively. For edge-light mini-LEDs with a pitch of 8.6 mm, the average luminance was 18,836 nits for an input power of 22.5 watts, the uniformity was 85%, the uniformity merit function was 10.13, and the contrast ratio was 60,000:1. Thus, a zero-optical-distance (ZOD) mini-LED backlight for extra-thin, large-area notebook LCDs was produced.

Wide-Angle Mini-Light-Emitting Diodes without Optical Lens for an Ultrathin Flexible Light Source

This report outlines a proposed method of packaging wide-angle (WA) mini-light-emitting diode (mini-LED) devices without optical lenses to create a highly efficient, ultrathin, flexible planar backlight for portable quantum dot light-emitting diode (QLED) displays. Since the luminous intensity curve for mini-LEDs generally recommends a beam angle of 120°, numerous LEDs are necessary to achieve a uniform surface light source for a QLED backlight. The light-guide layer and diffusion layer were packaged together on a chip surface to create WA mini-LEDs with a viewing angle of 180°. These chips were then combined with a quantum dot (QD) film and an optical film to create a high-efficiency, ultrathin, flexible planar light source with excellent color purity that can be used as a QLED display backlight. A 6 in (14.4 cm) light source was used as an experimental sample. When 1.44 W was supplied to the sample, the 3200-piece WA mini-LED with a flexible planar QLED display had a beam angle of 180° on the luminous intensity curve, a planar backlight thickness of 0.98 mm, a luminance of 10,322 nits, and a luminance uniformity of 92%.

Application of Mini-LEDs with Microlens Arrays and Quantum Dot Film as Extra-Thin, Large-Area, and High-Luminance Backlight

The demand for extra-thin, large-area, and high-luminance flat-panel displays continues to grow, especially for portable displays such as gaming laptops and automotive displays. In this paper, we propose a design that includes a light guide layer with a microstructure above the mini-light-emitting diode light board. The light control microstructure of concave parabel-surface microlens arrays on a light-emitting surface increases the likelihood of total internal reflection occurring and improved the uniformity merit function. We used a 17 in prototype with quantum-dot and optical films to conduct our experiments, which revealed that the thickness of the module was only 1.98 mm. When the input power was 28.34 watts, the uniformity, average luminance, and CIE 1931 color space NTSC of the prototype reached 85%, 17,574 cd/m², and 105.37%, respectively. This module provided a flat light source that was extra thin and had high luminance and uniformity.

Use of Recycling-Reflection Color-Purity Enhancement Film to Improve Color Purity of Full-Color Micro-LEDs

A common full-color method involves combining micro-light-emitting diodes (LEDs) chips with color conversion materials such as quantum dots (QDs) to achieve full color. However, during color conversion between micro-LEDs and QDs, QDs cannot completely absorb incident wavelengths cause the emission wavelengths that including incident wavelengths and converted wavelength through QDs, which compromises color purity. The present paper proposes the use of a recycling-reflection color-purity-enhancement film (RCPEF) to reflect the incident wavelength multiple times and, consequently, prevent wavelength mixing after QDs conversion. This RCPEF only allows the light of a specific wavelength to pass through it, exciting blue light is reflected back to the red and green QDs layer. The prototype experiment indicated that with an excitation light source wavelength of 445.5 nm, the use of green QDs and RCPEFs increased color purity from 77.2% to 97.49% and light conversion efficiency by 1.97 times and the use of red QDs and RCPEFs increased color purity to 94.68% and light conversion efficiency by 1.46 times. Thus, high efficiency and color purity were achieved for micro-LEDs displays.

Highly Reflective Thin-Film Optimization for Full-Angle Micro-LEDs

Displays composed of micro-light-emitting diodes (micro-LEDs) are regarded as promising next-generation self-luminous screens and have advantages such as high contrast, high brightness, and high color purity. The luminescence of such a display is similar to that of a Lambertian light source. However, owing to reduction in the light source area, traditional secondary optical lenses are not suitable for adjusting the light field types of micro-LEDs and cause problems that limit the application areas. This study presents the primary optical designs of dielectric and metal films to form highly reflective thin-film coatings with low absorption on the light-emitting surfaces of micro-LEDs to optimize light distribution and achieve full-angle utilization. Based on experimental results with the prototype, that have kept low voltage variation rates, low optical losses characteristics, and obtain the full width at half maximum (FWHM) of the light distribution is enhanced to 165° and while the center intensity is reduced to 63% of the original value. Hence, a full-angle micro-LEDs with a highly reflective thin-film coating are realized in this work. Full-angle micro-LEDs offer advantages when applied to commercial advertising displays or plane light source modules that require wide viewing angles.

Mini-LEDs with Diffuse Reflection Cavity Arrays and Quantum Dot Film for Thin, Large-Area, High-Luminance Flat Light Source

Mini-light-emitting diodes (mini-LEDs) were combined with multiple three-dimensional (3D) diffuse reflection cavity arrays (DRCAs) to produce thin, large-area, high-brightness, flat light source modules. The curvature of the 3D free-form DRCA was optimized to control its light path; this increased the distance between light sources and reduced the number of light sources used. Experiments with a 12.3-inch prototype indicated that 216 mini-LEDs were required for a 6 mm optical mixing distance to achieve a thin, large-area surface with high brightness, uniformity, and color saturation of 23,044 cd/m2, 90.13%, and 119.2, respectively. This module can serve as the local dimming backlight in next generation automotive displays.

Achievement of narrow-band blue-emitting phosphors KScSr1-y Ca y Si2O7:Bi3+ by the migration of luminescence centers

In recent years, efforts have been made to develop narrow-band emission phosphors with excellent performance. Herein, a series of KScSr1-y Ca y Si2O7:0.07Bi3+ narrow-band phosphors were synthesized by a co-substitution method, and the crystal structure, the occupancy of activated ions and luminescence properties were studied in detail. The substitution of Ca2+ for Sr2+ ions resulted in the migration of the activated Bi3+ from the K site to Sr site, accompanied by the regulation of the emission peak from 410 nm to 455 nm, the peak emission half width from 52 nm to 40 nm, and the color purity from the original 78% to 88%. In addition, a warm white LED with low CCT = 3401 K, CRI = 95.5, and CIE color coordinates of (0.3447, 0.3682) has been obtained through the combination of KSS0.6C0.4S:0.07Bi3+ with a commercial green and red phosphor on a UV (370 nm) chip. The results not only provided a strategy based on the manipulation of chemical composition and crystal structure to tune spectral distribution, but also broadens the choice of activators of narrow-band blue-emitting phosphors.