Improvement in Brightness Uniformity by Compensating for the Threshold Voltages of Both the Driving Thin-Film Transistor and the Organic Light-Emitting Diode for Active-Matrix Organic Light-Emitting Diode Displays

Abstract

In this paper, we propose a novel pixel design and driving method for active-matrix organic light-emitting diode (AM-OLED) displays using low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs). The proposed threshold voltage compensation circuit, which comprised five transistors and two capacitors, has been verified to supply uniform output current by simulation work using the automatic integrated circuit modeling simulation program with integrated circuit emphasis (AIM-SPICE) simulator. The driving scheme of this voltage programming method includes four periods: precharging, compensation, data input, and emission. The simulated results demonstrate excellent properties such as low error rate of OLED anode voltage variation (<1%) and high output current. The proposed pixel circuit shows high immunity to the threshold voltage deviation characteristics of both the driving poly-Si TFT and the OLED.

Pixel structures to compensate nonuniform threshold voltage and mobility of polycrystalline silicon thin-film transistors using subthreshold current for large-size active matrix organic light-emitting diode displays

“…A luminanceadjusting algorithm using a light sensor 17,18) also compensates the variations of the threshold voltage and mobility of TFTs by modulating video input data, but the operations of capturing the image and extracting parameters decrease the throughput owing to their long operation time. Voltageprogramming pixel structures with threshold voltage compensation [19][20][21][22][23][24] compensate the variation of the threshold voltage of TFTs in pixels, but the pixel structures do not compensate the mobility variation of TFTs in pixels. Voltage-programming pixel structures with threshold voltage and mobility compensation [25][26][27] compensate the variations of the threshold voltage and mobility of TFTs in pixels, but the pixel structures are too complex to integrate into a highresolution AMOLED panel.…”

Improvement in performance and reliability with CF4plasma pretreatment on the buffer oxide layer for low-temperature polysilicon thin-film transistor

“…However, this approach suffers from a serious reliability issue because the weak Si-H bonds are easily broken by the hot carrier impact during stressing [6]. For AMOLED application, the threshold voltage shift under stressing is a critical factor in determining the lifetime of AMOLED displays because the threshold voltage variation of LTPS TFTs will cause a huge deviation in the OLED current among pixels and image sticking [7]. Therefore, the improvement of reliability in LTPS TFT is an important issue for AMOLED application.…”