A Novel Voltage-Programmed Pixel Circuit Utilizing $V_{T}$-Dependent Charge-Transfer to Improve Stability of AMOLED Display

A novel voltage-programmed pixel circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) for active-matrix organic light-emitting diode (AMOLED) displays is proposed. The threshold voltage shift (ΔV
_T
) of the drive TFT caused by electrical stress is compensated by an incremental gate-to-source voltage (ΔV
_GS
) generated by utilizing the ΔV
_T
-dependent charge transfer from the drive TFT to a TFT-based metal-insulator-semiconductor (MIS) capacitor. A second MIS capacitor is used to inject positive charge to the gate of the drive TFT to improve the OLED drive current. The non-ideality of the ΔV
_T
-compensation, TFT overlap capacitance, programming speed, and OLED degradation are discussed. The effectiveness of the proposed pixel circuit is verified by simulation results.