A New Low Temperature Polycrystalline Silicon Thin Film Transistor Pixel Circuit for Active Matrix Organic Light Emitting Diode

Abstract

This study presents one novel compensation pixel design and driving method for active matrix organic light-emitting diode (AMOLED) displays that use low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) with a voltage feed-back method and the simulation results are proposed and verified by SPICE simulator. The measurement and simulation of LTPS TFT characteristics demonstrate the good fitting result. The proposed circuit consists of four TFTs and two capacitors with an additional signal line. The error rates of OLED anode voltage variation are below 0.3% under the threshold voltage deviation of driving TFT (ΔV TH = ±0.33 V). The simulation results show that the pixel design can improve the display image non-uniformity by compensating the threshold voltage deviation of driving TFT and the degradation of OLED threshold voltage at the same time.

A Novel LTPS-TFT Pixel Circuit to Compensate the Electronic Degradation for Active-Matrix Organic Light-Emitting Diode Displays

“…In the conventional 2T1C pixel circuit, the average error rate is about 30%. Therefore, the display image quality of the proposed pixel circuit will be more uniform than that in the other reports [12]. The results can prove that the proposed pixel circuit has high immunity to the threshold voltage deviation of DTFT.…”

“…In the conventional two-TFT pixel circuit for AMOLED, the various threshold voltages of driving TFT (DTFT) cause nonuniform gray-scale over the display area. Thus, several compensating methods have been developed and can be classified into voltage programming [5][6][7][8][9][10][11][12] and current programming [13][14][15][16]. Though the current programming method can compensate for the variation of both mobility and threshold voltage, but it has demerits in that low data current will result in long settling time because of the high parasitic capacitance of data lines.…”

A novel current-biased voltage-programmed pixel circuit with low temperature polycrystalline silicon thin film transistors for AMOLED

“…In the conventional two transistors and one capacitor (2T1C) pixel circuit in Fig. 1, the brightness uniformity is always deteriorated by the variations in threshold voltage and mobility of the driving TFTs as well as the current-resistance (I-R) voltage drop in the power line [7,8,9].…”

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

“…This issue is exacerbated as the size of a display increases. Instead of improving TFT processes, several studies have attempted to reduce the brightness variation across display panels by altering pixel circuit designs, which can use voltage driving, current driving, and digital driving compensation approaches [8][9][10][11][12][13][14][15]. The current driving method can minimize the shift in the DTFT threshold voltage; however, it requires a longer pixel charging time than that of voltage driving method because of the high parasitic capacitance of a data line.…”