A Driving Method of Pixel Circuit Using a-IGZO TFT for Suppression of Threshold Voltage Shift in AMLED Displays

A driving method of pixel circuit using amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) is proposed to improve the image quality of active matrix light-emitting diode displays. The proposed pixel circuit employs a diode-connected structure to compensate for variation in threshold voltage (Vth) of the a-IGZO TFT. In addition, the proposed driving method adopts negative bias annealing to suppress the Vth shift. The annealing time is optimized based on the experimental observation of the minimum Vth shift. After a stress time of 30000 s, the measurement results show that the Vth shift is reduced by 29.6%, using an optimized annealing time of 5% of one frame time. In addition, the maximum deviation in the emission current using the proposed driving method was measured to be less than 4.32% after a stress time of 30 000 s.