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

Abstract

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 (V-th) of the a-IGZO TFT. In addition, the proposed driving method adopts negative bias annealing to suppress the V-th shift. The annealing time is optimized based on the experimental observation of the minimum V-th shift. After a stress time of 30 000 s, the measurement results showthat the (Vth) shift is reducedby 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 wasmeasured to be less than 4.32% after a stress time of 30 000 s.