A Compensation Method for Variations in Subthreshold Slope and Threshold Voltage of Thin-Film Transistors for AMOLED Displays

Abstract

In this paper, we propose a compensation method for variations in the subthreshold slope (SS) and threshold voltage (Vth) of the low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) in an attempt to improve the image quality of the active matrix organic light-emitting diode (AMOLED) displays for mobile applications. The proposed compensation method provides a uniform voltage to the OLED according to the gray level without being affected by variations in the SS and Vth of the LTPS TFTs. To verify the performance of the proposed compensation method, a test pattern, including two pixel circuits designed for 5.7-inch quadruple high-definition AMOLED display was fabricated and measured. The measurement results showed that the proposed compensation method achieved an emission current error of the pixel circuit of only ±3.1 LSB at the 255th gray level. Therefore, the proposed compensation method is very suitable for AMOLED displays requiring high image quality.

Keywords

• Thin film transistors
• organic light-emitting diode displays
• pixel circuit
• high image quality