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This letter presents a novel hydrogenated amorphous silicon (a-Si:H) active-matrix organic light-emitting diode (OLED) pixel circuit that compensates for the threshold voltage shift of TFT using an internal compensated structure and reduces luminance decay by external detection method, based on the interdependence between the luminance degradation of OLED and the decrease in current under constant voltage bias stress. Experimental results demonstrate that the luminance of the OLED device with the proposed external detection method is more stable than that with the conventional 2T1C pixel circuit.Index Terms-Active-matrix organic light-emitting diode (AMOLED), external detection, hydrogenated amorphous silicon (a-Si:H).

In this letter, the electric characteristics of the fabricated organic light-emitting diode (OLED) devices are analyzed after a bias stress. Experimental results demonstrate that when a constant voltage is applied to the OLED device, the OLED threshold voltage gradually increases, resulting in the driving current to decay. Therefore, a novel voltage driving scheme for active-matrix OLEDs using low-temperature polysilicon thin-film transistors (poly-Si TFTs) is proposed. This circuit uses three TFTs to increase the aperture ratio of panels and the driving current of the OLED device to ameliorate the luminance drop that is caused by OLED degradation. Simulation results indicate that the proposed pixel circuit has high immunity to V TH variations of the poly-Si TFTs and provides an extra compensation current against OLED degradation.

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