The micro-LED displays are available in commercial market. Their image characteristics are excellent particularly in contrast ratio, response to electric field, and color expression. But the street price is too high to be acceptable for general consumers. The reasons may be the high chip price and the complicate manufacturing process. In this presentation, simple fluidic self-assembly technique is introduced for arranging the LED chips onto the transfer cartridge, leading into the LED module. Here, wave energy is used as an external force to manipulate the motion of LED chips in fluidic medium. By demonstrating the PM LED module, we hope that we have a chance to discuss the whole process of LED module fabrication.

GLVISON is a pioneer company that is leading the field of smart farm Quantum lighting by using Quantum Dot technology. We are producing various farm lightings with QD film and QD Cap for a specific crop by using free wavelength control ability. We are also commercializing more than 90 CRI (Color Rendering Index) lighting fixture with high price competitiveness by using normal 80+ CRI PKG LED. In near future, we will grow into a company that prioritizes shareholder profit by listing on KOADAQ.

In recent years, interest of high-efficient micro inorganic LEDs has increased for use in high-resolution displays such as virtual reality(VR) and augmented reality(AR). Many researchers have attempted monolithic methods, which have advantages in realizing high-resolution displays over other methods. However, since a single wafer has only one LED structure among RGB colors, it is difficult to fabricate full-color LEDs without color-conversion layer in conventional methods. So, developing monolithic LED structure which has multiple emission colors is necessary to minimize loss in color conversion.
In this study, we demonstrate a blue-green color tunable monolithic InGaN/GaN LED having a multi-junction structure on a single wafer. This result was achieved by metal-organic chemical vapor deposition (MOCVD) with selective area growth (SAG) method to make a blue-LED structure on a conventional green-LED. The device can emit all colors between blue and green light in the range of 460 to 520 nm by controlling the current injection.

Information & Opto-Energy Materials (IOEM) Laboratory studies on the light emitters and power electronics devices for further enhancement of performances. Over the past quarter-century, gallium nitride (GaN) and related Group III-nitride (III-N) wide-bandgap semiconductor materials have gained significant attention and consideration for power electronic devices and photonic devices fabrication due to eco-friendly high energy conversion efficiency, ruggedness, and superior transient performance. We perform researches on the development of new materials and fabrication. The leading-edge device technologies are changing from big-sized to nano-sized with increasing the demand of portable and mobile electronic devices. Recently, our researches are focused on fabrication of micro and nanostructure-based light emitters and electronic devices (including flexible and neuromorphic device). The IOEM have been developing new fabrication technology for industry-based manufacturing as it required. For this reason, we are consistently making long-term networks with physics, materials science, electronic engineering, and industry.

The transfer process is the most important stage in fabricating a display based on micro LEDs. Herein, the micro-sized chip is transferred to a unique patterned receptor by using the fluidic self-assembly (FSA), which is induced by magnetic field. Unique pyramidal shape and FSA technique can significantly improve the yield and throughput of transferred LED on to the receptor with holes of reverse pyramidal shape. As a result, we produced the yield value of 100% within the assembly time of 10 minutes with a receptor of 3 x 3 cm2 in size containing 100 holes.

Another important bottleneck in micro LED application in display is the low efficiency of red LED. We also demonstrate improved light output in AlGaInP based red LEDs by exploring surface plasmon coupling with Au/SiO2 metal nanoparticles. Star-shaped Au/SiO2 nanoparticles were introduced in the periodically patterned holes fabricated in AlGaInP based red LEDs. In particular, the energy coupling between the surface plasmon of the Au/SiO2 nanostars and the LED active layer greatly enhanced the light output in the red LED. The resultant micro-sized red LED chip (50 x 50 μm2 in size) consisting of Au/SiO2 exhibited a 50% higher light output compared with reference red LED.

3DOT LAB. in Kyungpook National University have participated SF-zone exhibition in 2017, 2018, and 2019. We have focused on the technologies for realizing 3D display systems and we have very strong points in not only optical and mechanical designs, but also electronics and programming for controlling. In this year, we plan to present our recent research achievements on 3D displays such as cylindrical light field display and holographic near-eye display. Especially, the demonstration in display technology is very important and I deeply appreciate IMID organization to give a chance to the University for free. I believe that it will be great opportunities for us to communicate with other researchers and discuss the prospect of 3D display technology together.

We propose a new thin and flat virtual reality (VR) display design using a Fresnel lenslet array, a Fresnel lens, and a polarization-based optical folding technique. The proposed optical system has a wide field of view (FOV) of 102°x102°, a wide eye-box of 8.8 mm, and an ergonomic eye-relief of 20 mm. Simultaneously, only 3.3 mm of physical distance is required between the display panel and the lens, so that the integrated VR display can have a compact form factor like sunglasses. Moreover, since all lenslet of the lenslet array is designed to operate under on-axis condition with low aberration, the discontinuous pupil swim distortion between the lenslets is hardly observed. In addition, all on-axis lenslets can be designed identically, reducing production cost, and even off-the-shelf Fresnel optics can be used.

We plan to demonstrate a real-time pressure mapping system using two types of flexible and high-resolution pressure sensor sheet. One is ferromagnetic particles/elastomer composite based soft pressure sensor sheet. With the external magnetic field, ferromagnetic conductive particles are vertically aligned in the uncured elastomer, forming anisotropic conduction paths. The other is cellulose/SWCNT thin film-based contact resistance type sensor sheet. The film has very sensitive piezoresistive properties due to the porous structure of cellulose. In addition, due to the spray coating-based process with a cellulose/SWCNT dispersion, easy patterning and large-area process are possible. By using a 48x48 channel read-out circuit board and visualization software, we can visualize the pressure distribution of a human palm and even small letters on a rubber stamp in real-time. It is expected that this technology can be used in the future technology such as e-skin, HMI, or force/touch sensors for flexible displays.

We demonstrate circuits for flexible display using amorphous Indium-Gallium-Zinc-Oxide IGZO TFTs. As a backplane of flexible display, a-IGZO TFTs have been regarded as very promising because they have higher mobility than amorphous silicon (a-Si) TFTs and lower cost, better uniformity, and lower processing temperatures than low-temperature polycrystalline silicon (LTPS) TFTs. However, in flexible displays, mechanical stress due to the physical deformation is inevitably applied to the a-IGZO TFTs, which affects their characteristics.
Therefore, circuits using a-IGZO TFTs for flexible display are designed to consider TFT degradations. First, we demonstrate dynamic logic circuits robust to mechanical stress. Second, we demonstrate gate driver circuits which is also robust to mechanical stress by combining carry-free and carry-type structures. To verify robustness to mechanical stress, the circuits are measured under tensile stress with bending radius of 1.5mm.