Adaptive Frequency Driving Scan Driver Combined with Logic Circuit based on a-InGaZnO TFTs

Jinho Moon, Eseudeo Yun, Yongchan Kim, and Hojin Lee

Abstract

Recently, due to the interest on flexible, wearble, and portable electronics as futre technologies, the demand for high-resolution display is expended. Although, faster frame rate and smaller area for the display is required, increased power consumption is incurred in high-performance display. Typically, for high-resolution displays, amorphous indium gallium zinc oxide thin film transistor (a-InGaZnO TFT) is actively researched because of its’ visible transparency, good uniformity, and utmost low off-current advantages rather than low temperature polycrystalline silicon (LTPS) TFT and amorphous silicon (a-Si) TFT. However, the a-InGaZnO TFT operates in depletion-mode because V_TH has negative values by the different indium component ratio and by the electrical characteristic variation due to the different bias stress such as illumination and bias stress. In this paper, we propose a adaptive frequency driving scan driver based on a-InGaZnO TFT with depletion-mode operation.

Novel AMOLED Pixel Circuit Compensating for Variations in Sub-threshold Swing and Threshold Voltage of a-IGZO Thin-Film Transistors

Hyunwoo Kim, Yongchan Kim, and Hojin Lee

Abstract

Amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) have been employed for the backplane of AMOLED displays because of high carrier mobility, good uniformity, and low off currenet. However, it is inevitable to have variations in threshold voltage (VTH) and sub-threshold swing (S.S.) due to bias-stress during display operations as well as the fabrication deviations. The VTH shift can be attributed to charge trapping in gate dielectric and interface states of semiconductor materials while the S.S. variation can cause a problem of leakage current that increases power consumption. Therefore, a circuit-level compensation method for deviation is required. In this paper, we have proposed a novel a-IGZO TFT pixel circuit which can compensate for the VTH and S.S. variation of the drive TFT.

Ultra-High Resolution Organic Light-Emitting Diodes Based on Plasmonic Patterned Nanograting Array

Ryungyu Lee, Keun-Yeong Choi, and Hojin Lee

Abstract

Organic light-emitting diodes (OLEDs) have led to the rapid growth of the next-generation display technology due to high luminance efficiency, vivid color, and high contrast ratio, thereby expanding their applications from conventional mobile or TV displays to virtual reality (VR)/ augmented reality (AR) displays. For more effective light extraction, implementing nanostructures onto metal electrode layer of OLEDs as a future display technology has been demonstrated by use of excitation and out-coupling of the surface plasmon-polariton modes (SPPs). In this work, we propose a high resolution OLEDs based on plasmonic patterned nanograting array (PNA) that induces a plasmonic effect on OLEDs through the nano-patterned organic emission layer by applying E-beam lithography on the fabrication process without deterioration of intrinsic physical/photoelectric properties of organic layers.