主動式有機發光二極體顯示器之畫素電路必須採用薄膜電晶體作為驅動與開關元件，然而在不同的半導體製程下，薄膜電晶體元件會因為製程上的誤差或長時間的操作而造成元件特性衰減，例如臨界電壓的變異或漂移，導致面板亮度的均勻性下降。此外，有機發光二極體材料會隨著長時間的使用而老化，造成整體面板的亮度下降，進而對於畫面品質造成影響。現今二維顯示器中已經有許多相關畫素補償電路被提出來改善上述的缺失，但是對於高解析度或高操作頻率的三維顯示器而言，受限制的補償時間會使畫素補償電路的儲存電容充放電不足，導致元件的補償效果不佳而使畫面品質下降。
本論文針對上述問題提出三個新式畫素補償電路，其中一個適用於二維顯示器另外兩個則適用於三維顯示器。第一個提出的電路適用於高解析度二維顯示器，其利用4T2C的電路架構來補償低溫多晶矽薄膜電晶體臨界電壓的變異，在有機發光二極體因材料老化而造成亮度衰減時，所提出的電路也可以提供額外的電流來增加亮度。從模擬結果可知，當薄膜電晶體臨界電壓變異時，所有資料電壓相對的電流誤差率最大約只有5 %，而當有機發光二極體材料老化時，所提出的電路電流也能有效的上升來補償亮度的衰減。然而由於此電路會有漏電流的問題而無法適用於三維顯示器的操作，因此第二個5T2C電路將非晶相銦鎵鋅氧化物薄膜電晶體應用在畫素電路上，除了補償有機發光二極體材料老化所造成亮度衰減的現象並改善漏電流問題而可操作在240赫茲三維顯示模式，由模擬結果可知電路中相關節點電壓變化值都幾乎等於相對應的薄膜電晶體和有機發光二極體臨界電壓變化值，所以本電路可以補償薄膜電晶體臨界電壓的變異並且增加有機發光二極體的顯像壽命。然而由於第二個電路使用過多的畫素元件，導致訊號線複雜及開口率下降，因此第三個電路即利用4T1C的架構以及反向偏壓來補償電晶體臨界電壓值的變異和改善有機發光二極體亮度的衰減。藉由所製作出的有機發光二極體之實驗，結果顯示在經過250分鐘後，受反向偏壓操作之有機發光二極體亮度衰減為原來的19.75%，相較之下，正常直流操作下之有機發光二極體亮度衰減度卻是原來的41.97%。因此，反向偏壓的方式的確可以有效改善有機發光二極體老化現象。由模擬可知電路中相關節點電流變化值幾乎維持一致，所以本電路可以補償臨界電壓值變異和改善電源線內阻效應的影響，並且增加有機發光二極體之顯像壽命。

For the pixel circuit of an active matrix organic light emitting diode (AMOLED) display, thin film transistors (TFTs) are used as the driving and switching component. However, the electrical characteristics of TFTs vary due to process variation or long-term operation. Moreover, the OLED material degrades, causing luminance decay of the OLED. Consequently, the image quality of the AMOLED display is influenced by the aforementioned problems. Several compensating pixel circuits have been proposed to improve the shortcomings of two-dimensional (2D) AMOLED displays. However, for the high-resolution or high-speed operation of three-dimensional (3D) AMOLED displays, the limited programming time causes incomplete compensation for the threshold voltage of TFTs, and thus influences the image quality of 3D AMOLED displays.
This thesis proposes three new pixel circuits and verifies their effectiveness by simulations and experiments. The first proposed 4T2C low temperature poly-silicon (LTPS) pixel circuit has immunity against the threshold voltage variation of the driving TFT for high-resolution 2D AMOLED displays. Moreover, when the luminance decay is caused by the degradation of OLED materials, the proposed circuit can provide extra current to increase the luminance. Based on the simulation results, the maximum current error rate is about 5% with TFT threshold voltage variation, and the OLED current effectively increases as the OLED material degrades. However, this circuit is not suitable for 3D AMOLED display operation due to the current leakage effect. Thus, the second proposed 5T2C circuit adopts amorphous indium gallium zinc oxide (a-IGZO) TFTs to solve the current leakage effect of the first circuit. This circuit can compensate for the threshold voltage shift of a driving TFT and luminance decay in 3D AMOLED displays. The electrical characteristics of a-IGZO TFTs were experimentally measured and fitted for the HSPICE modeling. According to the simulation that was developed from the fitted results, the stability of the OLED current and the amelioration of OLED degradation were confirmed. Furthermore, the drop of the normalized luminance achieved using the proposed driving scheme is below 3 % when the OLED is aged with a 0.5 V threshold voltage shift. Therefore, the proposed pixel circuit has high immunity to variations in the electrical characteristics of TFTs and can compensate for OLED degradation.
Due to the fact that the first and second circuits utilize excessive elements, it would result in complex control lines and a lower aperture ratio. Therefore, the third proposed 4T1C circuit adopts simultaneous emission and reverse-biased methods for reducing the degradation of OLEDs. During high-speed 3D operation at 240Hz, the proposed circuit can successfully compensate for TFT threshold voltage variation and improve the IR drop in the power line. Furthermore, the luminance degradation after 250 minutes is 19.75% under the 50% AC condition and 41.97% under the DC condition. Thus, the application of the reverse-biased method can successfully reduce the luminance degradation of AMOLEDs. The proposed pixel circuit has high immunity to VTH variation of TFTs, and thus achieves uniform brightness throughout the panel.

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