Woo-Jin Nam

A new voltage-modulated AMOLED pixel design compensating for threshold voltage variation in poly-Si TFTs

A new voltage-modulated active-matrix organic light-emitting diode (AMOLED) pixel design, which successfully compensates for the threshold voltage variations in poly-Si thin-film transitors (TFTs), is proposed, and verified by SPICE simulation and experiments. In order to compensate for variations in OLED current, the proposed pixel design employs a new voltage modulation scheme using diode connections.

A New Poly-Si TFT Current-Mirror Pixel for Active Matrix Organic Light Emitting Diode

A new poly-Si thin-film-transistor (TFT) current-mirror-active-matrix-organic-light-emitting-diode (AMOLED) pixel, which successfully compensates for the variation of the threshold voltage as well as mobility in the excimer laser annealed poly-Si TFT pixel, is designed and fabricated. The OLED current (IOLED) of the proposed pixel does not depend on the operating temperature. When the temperature of pixel is increased from 27 degC to 60 degC, the I OLED of the new pixel circuit composed of four TFTs and one capacitor increases only about 1.5%, while that of a conventional pixel composed of two TFTs and one capacitor increases about 37%. At room temperature, nonuniformity of the IOLED in the proposed circuit was also considerably suppressed at around 9%. We have successfully fabricated a 1.2-in AMOLED panel (96times96timesred green blue) to evaluate the performance of the proposed pixel. A troublesome residual image caused by the hysteresis phenomenon of the poly-Si TFT was almost eliminated in the proposed AMOLED panel as a result of current programming

A new current scaling pixel circuit for AMOLED

A new active-matrix organic light-emitting diode (AMOLED) pixel design, composed of four polycrystalline silicon thin-film transistor (poly-Si TFT) and one capacitor, is proposed by employing a novel current scaling scheme. The simulation results, based on the measured characteristics of an OLED and poly-Si TFTs, show that the proposed pixel design would scale down the data current more effectively, so as to guarantee a lower charging time compared with the conventional current mirror structure, as well as successfully compensate the variation of the electrical characteristics of the poly-Si TFTs, such as the threshold voltage and mobility.

A poly-Si TFT fabricated by excimer laser recrystallization on floating active structure

This letter reports a. new excimer laser annealing (ELA) method to produce large polycrystalline silicon (poly-Si) lateral grains exceeding 4 /spl mu/m. A selectively floating amorphous silicon (a-Si) flint with a 50 nm-thick air-gap was irradiated by a single-pulse XeCl excimer laser and uniform lateral grains were grown due to the lateral thermal gradient caused by the low thermal conductivity of the air. A poly-Si thin-film transistor (TFT) with two high-quality 4.6 /spl mu/m-long lateral grains was fabricated by employing the proposed ELA and high field-effect mobility of 331 cm/sup 2//Vsec was obtained due to. the high-quality grain structure.

A high-performance multichannel dual-gate poly-Si TFT fabricated by excimer laser irradiation on a floating a-Si thin film

A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec.

A new low-power pMOS poly-Si inverter for AMDs

A new low-power inverter using only p-type poly-Si thin-film transistors for the driving circuits of active matrix liquid crystal displays and active matrix organic light-emitting diodes is proposed and fabricated. The proposed pMOS inverter using capacitive coupling and bootstrapping successfully eliminated the troublesome through current and exhibited a wide output swing from V/sub DD/ to V/sub SS/ without additional signals.

P‐12: A New a‐Si:H TFT Pixel Design Compensating Threshold Voltage Degradation of TFT and OLED

A new active matrix organic light emitting diode (AM-OLED) pixel design, based on the a-Si:H TFTs, is proposed and verified by SPICE simulations. The simulation results show that the proposed pixel, which consists of 7-TFT and 1-capacitor and 1-additional signal line, compensates the problem of the threshold voltage degradation in the a-Si:H TFT and OLED.

Low-Voltage Driven P-Type Polycrystalline Silicon Thin-Film Transistor Integrated Gate Driver Circuits for Low-Cost Chip-on-Glass Panel

P-type low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) integrated driver circuits are proposed for low-cost chip-on-glass (COG) panel. In order to reduce the process cost of panel, gate driver employing level-shifter, shift register and DC–DC converter is integrated by p-type polycrystalline silicon (poly-Si) TFTs. The gate drivers are composed of the level-up and level-down voltage shifters and the robust two-clock shift registers. The DC–DC converters are designed using diode-connected type charge pumps and regulators. The proposed p-type circuits were verified successfully by the simulations and the measurements.

P-104: A New Voltage Modulated AMOLED Pixel Design Compensating Threshold Voltage Variation of Poly-Si TFTs

A new pixel design for active matrix organic light emitting diode (AMOLED) display using low temperature polycrystalline silicon thin film transistor (LTPS-TFT) is proposed. The proposed pixel, which consists of 4-TFTs and 1-capacitor, eliminates the TFT threshold voltage variation problem of conventional pixel without any additional control signal line.

P-14: Polarity-Balanced Driving to Reduce VTH Shift in a-Si for Active-Matrix OLEDs

A new driving scheme, which consists of dual scan line and 2 driving TFTs, employing a-Si TFT rather than the low temperature poly-Si for AMOLED is proposed. The proposed scheme was verified by circuit simulation with parameters extracted from experimental results. The recovery of threshold voltage by successive positive and negative bias may contribute the reliability of OLED display.