低溫多晶矽薄膜電晶體製程具有優越的電流驅動能力，常被用來製作主動式矩陣有機發光二極體顯示器之背板以縮減畫素電路之佈局面積。因此，低溫多晶矽薄膜電晶體被視為中小尺寸和高解析度主動式矩陣有機發光二極體顯示器之主流電晶體製程技術。然而，低溫多晶矽薄膜電晶體因為雷射退火製程之雷射能量不一致，使面板各處電晶體之電特性有所差異，如臨界電壓變異等，導致驅動有機發光二極體之發光電流失真進而影響面板顯像之均勻性。因此許多畫素電路被提出來補償低溫多晶矽薄膜電晶體之臨界電壓變異。然而，大部分的畫素電路在高解析度顯示器中的補償效果不佳，原因為補償時間受限於高解析度顯示器之掃描時間。以高解析度之三維顯示器而言，畫素電路搭配傳統的漸進式發光驅動法將會減少顯示器之解析度且增加使用額外資料IC之成本。另一方面，閃爍現象在主動式矩陣有機發光二極體顯示器也是個需要改善之問題，此現象會降低顯示器之對比度與增加額外的功耗。
本論文提出四個畫素電路與搭配之驅動法或驅動架構來改善主動式矩陣有機發光二極體顯示器中常見的問題。第一個所提出之畫素電路適用於高解析度之主動式矩陣有機發光二極體顯示器，其以電流偏壓驅動之方法與平行驅動法補償驅動電晶體之臨界電壓變異。此畫素電路也可改善電壓源變異之問題與防止面板發生閃爍。模擬結果顯示在臨界電壓與電壓源分別變異±0.5 V與-0.5 V的情況下，相對發光電流誤差率皆分別低於4 %與1.2 %。但此畫素電路之架構為較複雜的5T2C，難以應用於中小尺寸之高解析度主動式矩陣有機發光二極體顯示器，因此本論文提出一個欄共用之外部補償電路搭配2T1C畫素電路。此電路利用雷射退火製程之特點假設整欄驅動電晶體之臨界電壓相同並進行補償，進而將畫素電路之架構縮減至2T1C。電路模擬結果顯示在電晶體臨界電壓變異為±0.5 V時，最差的相對發光電流誤差率僅有1.82 %。
為了解決傳統漸進式發光驅動法應用在三維顯示器之問題，論文提出兩個適用於三維主動式矩陣有機發光二極體顯示器之搭配同步式發光驅動法之畫素電路。第三個所提出之新式4T2C畫素電路能有效地補償驅動電晶體之臨界電壓變異並防止面板發生閃爍現象，模擬結果顯示當薄膜電晶體臨界電壓變異±0.5 V時，此電路之相對發光電流誤差率皆低於3.6 %，且在編程階段時流過有機發光二極體之電流僅為0.01 nA，證明此電路能有效地防止畫面發生閃爍現象。為了實現具更高解析度或尺寸更微小之三維主動式矩陣有機發光二極體顯示器，論文所提出之第四個電路結合了兩鄰近畫素之畫素電路，並將每個畫素電路架構簡化至3.5T2C。此電路架構利用電容耦合效應、電荷分享效應與對稱之二極體架構，來補償驅動電晶體之臨界電壓變異與排除面板之閃爍現象。模擬結果顯示薄膜電晶體臨界電壓變異±0.5 V時，整個灰階電壓範圍之相對發光電流誤差率皆低於4.4 %，且在電路操作之編程階段無大電流流過有機發光二極體，證明了提出之電路能有效地補償電晶體之臨界電壓變異與防止顯示器發生閃爍現象。

Low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) are usually adopted in pixel circuits of active-matrix organic light-emitting diode (AMOLED) displays because of their excellent current driving capability, shrinking the average layout area of each pixel. Therefore, LTPS-TFTs are regarded as the mainstream TFT technology for high-resolution and small / medium-size AMOLED displays. However, threshold voltage (VTH) variation of LTPS-TFTs caused by excimer laser annealing (ELA) fabrication process results in the inevitable difference in OLED emission current among pixels, decreasing the image uniformity of displays. Numerous pixel circuits are proposed for compensating for VTH variation of LTPS-TFTs. However, most pixel circuits cannot achieve satisfactory VTH compensation for high-resolution AMOLED displays owing to limited compensation period. Considering the application of high-resolution three-dimensional (3D) AMOLED displays, pixel circuits with conventional progressive emission (PE) method reduces the resolution of displays and enhances more cost of adopting more data ICs. Furthermore, flicker phenomenon is also a critical issue of AMOLED displays, which reduces the contrast ratio and increases additional power consumption of displays.
This thesis proposes four pixel circuits with different driving scheme or structure for improving the aforementioned problems. The first pixel circuit with current-biased voltage-programming (CBVP) method and parallel driving scheme effectively compensates for VTH variation of driving TFTs for high-resolution AMOLED displays. This pixel circuit also ameliorates the issues of VDD IR-drop effect and flicker phenomenon. Simulation results demonstrate that the relative current error rates under VTH variation and VDD IR-drop are less than 4 % and 1.2 % respectively. However, the 5T2C structure of this pixel circuit is too complex to implement small / medium-size high-resolution AMOLED displays. Therefore, the external compensation circuit out of array shared by whole column combining with conventional 2T1C AMOLED pixel circuit is proposed. This circuit utilizes the feature of ELA process to compensate for VTH variation of driving TFTs of whole column, extremely simplifying structure of pixel circuits to 2T1C. Simulation results show that the worst case of relative OLED emission current error rates is merely 1.82 % as VTH varies ±0.5 V.
To generate 3D images without disadvantages of PE method, this thesis proposes two pixel circuits with simultaneous emission (SE) method for high-resolution 3D AMOLED displays. The third proposed pixel circuit with 4T2C structure effectively compensates for VTH variation of driving TFT and prevents flicker phenomenon. Simulation results show that relative error rates over entire data voltage range are all less than 3.6 % as VTH varies ±0.5 V. Additionally, results demonstrate that the current flowing through OLED is only about 0.01 nA during the programming period, thereby effectively preventing the flicker phenomenon. For realizing the 3D AMOLED displays with higher resolution or smaller size, this thesis combines two pixels of adjacent rows into one circuit for simplifying the circuit structure to 3.5T2C. The fourth pixel circuit can also compensate for VTH variation of LTPS-TFTs and nearly eliminate flicker phenomenon through utilizing capacitive coupling effect, charge sharing effect and symmetrical diode-connected structure. Simulation results present that the relative error rates of OLED emission current are all less than 4.4 % at various data voltages as VTH varies ±0.5 V. Moreover, these results demonstrate that there is not any large and lasting current flowing through OLED during the programming period. Therefore, these results confirm the proposed circuit’s performance of compensating for VTH variation and preventing flicker phenomenon.

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