Novel Pixel Circuit With Compensation for Normally-Off/On a-IGZO TFTs and OLED Luminance Degradation

This letter presents a new pixel circuit reaching simultaneous compensation for a threshold voltage (V
_TH
) shift of normally-off and normally- on a-IGZO TFTs, as well as luminance drop of an OLED device for ultrahigh-definition active-matrix organic light-emitting diode displays. Simulation results demonstrate the successful detection of a 1 V shift of threshold voltage despite normally-off and normally-on characteristics by the novel source-follower structure. Furthermore, the interdependence between luminance and threshold voltage shift of the OLED device is measured. Based on the simulations using the measured interdependence, the luminance drop caused by OLED aging is suppressed below 5% at different data voltages.