| Summary: | 碩士 === 國立交通大學 === 光電工程系所 === 95 === Active matrix organic emitting diode (AMOLED) display panels have recently attracted much attention. Because OLED has significant advantages：self-illuminance, high contrast ratio, wide viewing angle (more than 170 degree), fast response time, high illuminant efficiency , low operation voltage, thin, flexible and simple fabrication. Furthermore, low cost of fabrication is regarded as best potential in production fields. Operation of conventional AMOLED display panels are two thin film transistors (TFTs) , which are individually for switching and driving function, and one storage capacitor. However, no matter hydrogenated amorphous TFTs (a-TFTs:H) or low temperature poly TFTs (LTPS) we use, there are their own obstacles. The significant advantages over LTPS are high driving current, mobility and large aperture ratio. Lower operation voltage makes power conservation. But higher cost on fabrication and lower uniformity makes it difficult to apply in large and high resolution panels. On the contrary, the advantage over LTPS are in the higher uniformity and lower fabrication cost. Nevertheless, a-TFT:H itself is in the worse reliability. After long time operation, the driving a-TFT:H would degrades to cause threshold voltage shift. The driving current becomes lower and lower. These are the most significant drawbacks of a-TFT:H. Furthermore, OLED itself also degrades after long time stress. As a consequence, compensation pixel circuits for threshold voltage shifts and OLED degradation have been extensively studied.
In this thesis, we are introducing two voltage-programmed compensation pixel circuits with a-TFTs:H. We are looking forward to utilizing advantages of a-TFTs:H：uniformity, low cost and simple fabrication and cooperating our compensation pixel circuit to significantly enhance stability and uniform brightness of AMOLED display panels. The simulation results indicate that these proposed circuits successfully compensate for the threshold voltage shift of a-TFTs:H.
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