Chi-Woo Kim

9.2: Sequential Lateral Solidification (SLS) Process for Large Area AMOLED

We have demonstrated that the sequential lateral solidification (SLS) technology can be utilized for the large area AMOLED. An optimized SLS process provides us with polycrystalline Si films with well-controlled grain size and location. The thin film transistors (TFTs) with SLS-processed Si films show high performance with desirable uniformity. 14″ WXGA (1280×RGB×768) AMOLEDs were fabricated with SLS-processed TFT backplanes. We utilized RGB evaporation process with fine metal mask. The novel delta pixel arrangement results in increased aperture ratio and wider FMM process window. The advantage of SLS process will be discussed.

A 3.0-in. 308-ppi WVGA AMOLED with a top-emission white OLED and color filter

— A 3.0-in. 308-ppi WVGA top-emission AMOLED display with a white OLED and color filters, driven by LTPS TFTs demonstrating a color gamut of >90% and a Δ(u′,v′) of <0.02 is reported. A white-emission source with a unique device structure was developed using all fluorescent materials and yielded efficiencies of 8.45% and 16 cd/A at 4000 nits with CIE color coordinates of (0.30, 0.32).

41.4: AMOLED based on Silicon-On-Glass (SiOG) Technology

We have demonstrated that the single crystalline silicon films on the glass substrates can be utilized in the conventional mass production lines. The single crystalline Si layers were transferred to the 370 mm × 470 mm glass substrates using Silicon-On-Glass (SiOG) technology. Using the thin film transistor backplanes made by conventional CMOS technology, 2.4″ qVGA AMOLED with integrated circuits were successfully fabricated. A completed 2.4″ qVGA AMOLED module shows wide viewing angle (> 170°) and 73% color gamut. The advantages of SiOG technology and its significances will be presented.

68.2: Achieving High Color Gamut with Microcavity on White OLED

We have demonstrated bottom-emission white OLED devices, which have RGBW sub-pixel and high color gamut over 100% NTSC ratio with White-to-Green microcavity technique. Large-Sized AMOLED TV has to show very high quality display images to overcome LCD TV. However, the R, G and B colors filtered by LCD color-filters are not saturated enough. Especially, green emission peak is very broad because blue emission peak is not removed perfectly by green color-filter. Therefore, we fabricate white OLED having saturated green color by adapting microcavity technique. The results of green pixels are (0.211, 0.723) in color coordinates, and the efficiency of green is 15.4 cd/A, which was (0.217, 0.600) and 7.5 cd/A. And the color gamut with microcavity reaches more than 100% NTSC.

A self-reset ambient-light sensor system for low-temperature polycrystalline-silicon active-matrix displays

— A new digital ambient-light sensor system has been designed and fabricated on a glass substrate using a conventional low-temperature polycrystalline-silicon (LTPS) technology. In the proposed system, analog-to-digital conversion (ADC) is performed in the time domain instead of the voltage domain and is combined with a light-detection process. The proposed system employs self-reset architecture and requires only one comparator for n-bit digital output. Because the complex analog circuitry is eliminated from the system, it can be readily integrated on the glass substrate.

9.2: Line-Scan Sequential Lateral Solidification Process for AMOLED Application

We have demonstrated that thin film transistor backplanes for AMOLED could be fabricated with line-scan sequential lateral solidification (SLS) process. with 4 μm × 730 mm single laser beamlet, directional and two-shot SLS processes were carried out to make polycrystalline Si films. The geometry for driving TFTs, which can provide sufficient uniformity of TFT performances, is that the source-drain direction is perpendicular to the grain growth direction. 14″ WXGA (1366×RGB×768) AMOLEDsfor TV application were fabricated by utilizing different TFT geometry for driving TFTs and switching TFTs. The advantages of the line-scan SLS system are (1) it can provide higher productivity than the conventional laser system and (2) large displays over 50″ can be manufactured without scan overlap area.

62.2: Adaptive White Extension for Peak Luminance Increase in RGBWAMOLED

RGBW AMOLED panel, compare to the RGB panel, has lower power consumption and current stress and as result — bigger life time. Using special algorithms and RGB subpixels (as additional white) permits to increase brightness of this panel up to 2 times. At the same time its very important to keep panel current at permissible range. We propose an algorithm, what permits to increase brightness of the RGBW AMOLED panel and limit its summary current at the same time.

Ambient-light sensor system with wide dynamic range enhanced by adaptive sensitivity control

— A new digital ambient-light sensor system is presented which employs two linear light sensors with different sensitivities and automatically adjusts the sensitivity based on the illumination condition. The adaptation mechanism allows a very wide range of light intensity to be detected, and the input dynamic range of the system is substantially improved from 22.5 to 45.1 dB. The proposed method does not require any additional precision bits for output data. Due to the small number of the output bits and the simple conversion process, the system can be easily integrated on the display panel.

P-259L: Late-News Poster: A 14inch Uniform AMOLED Display with Low Cost PECVD Based Microcrystalline Silicon TFT Backplanes

This paper discusses development of uniform 14.1 inch AMOLED display using PECVD based microcrystalline silicon (mc-Si) TFTs. Microcrystalline silicon was deposited using conventional 13.56 MHz Plasma Enhanced Chemical Vapor Deposition (PECVD) with novel gas precursors. The mc-Si TFTs show a field effect mobility of around 1cm2/V.s and off-current less than 1pA. Electrical stress on mc-Si TFTs for a long time shows no significant threshold voltage shift indicating a stable TFT backplane. Significant uniformity improvements were made with novel TFT structure to give uniform AMOLED display. The deposition time for mc-Si TFTs was significantly reduced by using a thin mc-Si layer. Mc-Si TFT backplanes using conventional PECVD equipment offers significant cost advantages over other competing laser and non-laser polysilicon TFT technologies for AMOLEDs.

32.2: Touch-Panel Controller Implemented with LTPS TFTs

A touch panel controller has been implemented with LTPS TFTs on a glass substrate. It induces voltage gradient across either plate of a 4-wire resistive touch panel and senses the intermediate potential at the touch position via the other plate. Then it converts the acquired analog voltage into digital signal and outputs 3-bit digital data for the horizontal and vertical positions respectively.