Demands for high-performance displays with high pixel density and picture quality are ever increasing.Indium gallium nitride (InGaN)-based micro-LEDs (μLEDs) are suitable for meeting such demands owing to their high e ciency, brightness, and stability. However, the poor yield of the pick-and-place technique, defect repair, and visibility of edge lines between modules limit the applications of μLEDs. Furthermore, the external quantum e ciency (EQE) decreases (<10%) when μLED size is reduced to less than 10 μm for high pixel densities, thereby limiting the luminance. Here, we demonstrate a top-down-processed blue InGaN/GaN multiple-quantum well (MQW) nanorod-LED (nLED) can be made highly e cient as well as become an enabling technology for reducing manufacturing cost of large-screen displays. A pixel array comprising of horizontally-aligned nLEDs between pixel electrodes can be cost-effectively fabricated by applying the dielectrophoretic force to the inkjet-printed nLEDs dispersed in ink solution. To overcome size-dependent EQE reduction problem, we studied the interaction between the GaN surface and the surface passivation layer via various analyses and found that minimizing the point defects created during the passivation process is crucial to manufacturing high-performance nanoscale LEDs. Notably, the sol-gel method is advantageous for the passivation because SiO2 nanoparticles are adsorbed on the GaN surface, thereby minimizing its atomic interactions. The fabricated nLEDs exhibited an EQE of 20.2±0.6%, the highest EQE value ever reported for the LED in the nanoscale. This work opens the way for manufacturing self-emissive nLED displays that can fully meet the industry requirements of high e ciency and brightness and low-power consumption, contributing to energy saving, carbon neutrality and mitigating climate crisis.

We applied conductive Atomic Force Microscopy (c-AFM) to characterize the electrical properties of low-temperature polycrystalline silicon. Current distribution and current-voltage characteristics are recorded using conductive-diamond covered AFM tip and low noise external amplifier. Spectroscopic ellipsometry and optical microscopy are used to determine the grain size, crystalline fraction and film thickness. The correlation between structural properties of the poly-Si fabricated with varied conditions and c-AFM results is revealed, which shows the potential of this technique as convenient method for evaluation of metal-induced-crystallized poly-Si quality.

We have investigated the effect of thin fluoro-acrylic polymer as an anode stabilizer on the lifetime of an organic light emitting device (OLED). Surface chemical properties of commercial fluoropolymer, FC-722 (Fluorad™ of 3M), on indium–tin oxide (ITO) were characterized by x-ray photoemission spectroscopy. An OLED with 1 nm thick fluoropolymeric film showed identical brightness and efficiency behaviour and improved operational stability compared with the reference device with UV-O3 treated ITO. The improvement in the lifetime was accompanied by the suppression of the voltage increase at the initial stage of constant-current driving, which can be attributed to the action of the FC-722 layer by smoothing the ITO surface. Fluoropolymer coating, therefore, improves the lifetime of the small molecular OLED by the simple and reliable anode-stabilizing process.

In order to understand instability occurring in OLED devices, time‐dependent atmospheric denaturalization studies of π‐conjugated DNTPD (N1,N1′‐(biphenyl‐4,4′‐diyl)bis(N1‐phenyl‐N4,N4‐di‐m‐tolylbenzene‐1,4‐diamine) thin films, functioned as a hole injection layer in OLEDs, and its effect on device performances were described. The formation of C‐OH (DNTPD‐OH) and C=O (DNTPD=O) bonds were supported by the density functional theory (DFT) calculations. With increasing the air‐exposure time, the DNTPD thin film stored in air (23 °C, 55%RH, dark room) became thicker and bumpy; aromaticity was rapidly diminished; relative atomic amount of carbon and nitrogen were continuously decreased, on the contrary, that of oxygen was gradually increased. The atmospheric denaturalization in DNTPD films includes the formation of hydration layer, oxidation and degradation of DNTPD molecules by attacks of reactive hydroxyl ions existed in the air and formed by self‐ionization of water, and volume expansion due to interpenetration of water between the DNTPD molecules. The OLED devices made of air exposed DNTPD thin films as a hole injection layer showed degraded device performances compared with the air‐free device, resulting from the disturbed energy diagram and degraded hole transport property by the oxidized/degraded DNTPD molecules.

Indium‐Tin‐Oxide (ITO) / Ag (Silver) / ITO triple layer, are often used as anode electrodes, but when the Ag is eluted, they cause many problems, such as poor dark spots. In this paper, the thermal behavior of the upper ITO, which is presumed to be the most relevant, was observed to identify the cause of this defect. The ITO layer is deposited in an amorphous state during initial deposition to create a pattern. After patterning, it is crystallized by heat treatment to obtain electrical and physical characteristics. However, it was confirmed that partial crystallization was already in progress at initial deposition due to changes in thickness. Partial crystallization was mainly observed at the meeting points of the three Ag grains. It was also confirmed that the process of heat treatment led to different crystallization than the initial partial crystallization. The crystallization areas formed in these heterogeneous states showed different thermal behavior. Stress caused by different thermal behaviors accelerated as heat treatment progressed, producing pin‐holes after the heat treatment was completed. Thus, the number of pin‐holes increases as heterogeneous states increase, resulting in a difference in the level of Ag elution defect. In conclusion, a decrease in the number of triple points an Ag Grain meets can reduce dissimilarity and consequently reduce the probability of pin‐hole occurrence. Therefore, expanding the size of the Ag Grain is effective in reducing the defect of Ag elution.