主動式有機發光二極體（AMOLED）由於其比液晶顯示器（LCD）具有的各種優勢，如對比度更高，響應時間更快，更薄，功耗更低，廣視角，可撓性等優勢，因此受到學界以及顯示器行業的關注。近年來，在畫素電路中採用低溫多晶矽薄膜電晶體（LTPS-TFT）和金屬氧化物薄膜電晶體作為AMOLED的背板技術。 LTPS-TFT具有高電流驅動能力和良好的電特性，低溫多晶矽薄膜電晶體因為在製程中經過分子雷射的退火再結晶會導致一些電性上的不均勻，這是一個非常嚴重且不可避免的問題。與LTPS-TFT相比，金屬氧化物薄膜電晶體具有優良的特性，包括良好的遷移率，優異的均勻性和良好的穩定性。它更適合用於製造大尺寸顯示器的製程。然而，當長時間操作時，薄膜電晶體將顯示出不均勻的電特性。
但對於實際的AMOLED 顯示器上，除了電晶體的電特性飄移之外，有機發光二極體的衰退以及寄生電阻和寄生電容帶來的影響也需要在我們設計畫素電路時一併考慮。因此，考慮上述問題後，我們從實驗室所得的氧化銦鎵鋅（IGZO）數據中先建立了一個model 並提出第兩個畫素電路是以氧化銦鎵鋅（IGZO）為電晶體的補償電路，其第一個架構包含了四顆薄膜電晶體和二顆電容，其特點為第一個不藉由外部電路就能進行全面性補償的電路並提供逆偏壓延長有機發光二極體的壽命。根據模擬結果，在電晶體的臨界偏壓飄移正負2Ｖ時，電流的電流錯誤率僅1.3%。
第二個電路是以驅動電晶體的電特性去做改善，提出了一個新式補償電晶體mobility 非均勻性的畫素電路，架構包含了五顆薄膜電晶體和二顆電容，其特點是利用時脈分割，使補償mobility時不受data input的電壓值影響，進而達到良好的補償效果，在driving TFT mobility變化±50%所造成的最大電流錯誤率小於3.8%。最後，藉由電路模擬結果的印證並將其與過去期刊上的畫素電路作比較，顯示出設計的電路有著顯著的特性。

Active-matrix organic light-emitting diode (AMOLED) have attracted attentions among recent research and display industries due to their various advantages over liquid crystal display (LCD), such as higher contrast ratio, faster response time, thinner module, lower power consumption, wider viewing angles and potential flexibility. In recent years, low-temperature polycrystalline silicon (LTPS) TFT and oxide TFTs are adopted in the pixel circuit as a backplane technology for AMOLEDs. LTPS-TFTs have high current driving capability and good electrical characteristics but it suffer from threshold voltage (VT) and the mobility (μ) easily varied during the actual annealing process. Compared with LTPS TFTs, oxide TFTs have much better characteristics including decent mobility, excellent uniformity, and good stability. It is more suitable for fabricate large size display in fabrication process. However, oxide TFT will show non-uniform electrical characteristics when operated for a long time.
For a real display, there exist some other issues such as OLED degradation and IR drop. None of paper reported can comprehensively compensate for the issues of displays by voltage programming pixel circuit. Therefore, in the thesis, we build a model of a-IGZO TFT for SPICE which was fabricated from our lab at first. We propose two pixel circuit on a- IGZO TFT. In the first pixel circuit, it is composed of four TFT and two storage capacitors. It can not only successfully detect the VTH of normally-on and normally-off TFT, but apply reverse bias on OLED. Furthermore, the variation of mobility is also compensated. According to the simulation results, the average current error rates are only 1.3% (ΔVTH =±2V).
The second circuit is based on the electrical characteristics of the driving transistor. A new pixel circuit for compensating for the mobility non-uniformity of the transistor is proposed. The architecture consists of five transistors and two capacitors. The pulse division makes the compensation of the mobility not affected by the voltage value of the data input, and thus achieves a good compensation effect, and the maximum current error rate caused by the variation of the driving TFT mobility by ±50% is less than 3.8%. At last, all of them were verified by SPICE and compared with other pixel circuits from presented paper.

[1] R. Mertens, “The OLED Handbook A Guide to OLED Technology,” Industry & Market, 2013.
[2] C. W. Tang and S. A. VanSlyke, “Organic electroluminescent diodes,” Applied Physics Letters, Vol. 51, pp. 913-915 1987.
[3] Park, J. S., Chae, H., Chung, H. K. & Lee, S. I, “Thin film encapsulation for flexible AM-OLED: a review,” Semiconductor Science and Technology, 26, 034001 2011.
[4] Wuu, DS, Chen, TN, Lay, E, Liu, CH, Chang, CH, Wei, HF et al, “Transparent barrier coatings on high temperature resisting polymer substrates for flexible electronic applications” Journal of The Electrochemical Society, 157: C47 2010.
[5] N. S. Holliman , N. A. Dodgson, G. E. Favalora and L. Pockett, “Three-Dimensional Displays: A Review and Applications Analysis,” IEEE Transactions on Broadcasting, vol. 57, no. 2, pp. 362-371, Apr 2011.
[6] H. Urey , K. V. Chellappan, E. Erden and P. Surman, “State of the Art in Stereoscopic and Autostereoscopic Displays,” Proceedings of the IEEE, vol. 99, no. 4, pp. 540-555, Apr 2011.
[7] J. Hong, Y. Kim, H. J. Choi, J. Hahn, J. H. Park, H. Kim, S. W. Min, N. Chen and B. Lee, “Three-dimensional display technologies of recent interest Principles, status, and issues,” Applied Optics, vol. 50, no. 34, pp. 87-115, 2011.
[8] E. Lueder, 3D Displays, 2012, pp. 22-25.
[9] B. W. Lee, I. H. Ji, S. M. Han, S. D. Sung, K. D. Shin, J. D. Lee, B. H. Kim, B. H. Berkeley and S. S. Kim, “Novel Simultaneous Emission Driving Scheme for Crosstalk-free 3D AMOLED TV,” Society for Information Display, vol. 41, no. 1, pp. 758-761, 2010.
[10] C. Wang, Z. Hu, X. He, C. Liao, and S. Zhang, “One gate diode connected dual-gate a-IGZO TFT driven pixel circuit for active matrix organic light-emitting diode displays,” IEEE Trans. Electron Devices, vol. 63, no. 9, pp. 3800–3803, Sep. 2016.
[11] D. W. Kim, H. Oh, B. D. Youn, and D. Kwon, “Bivariate lifetime model for organic light-emitting diodes,” IEEE Transactions on Industrial Electronics, vol. 64, no. 3, pp. 2325–2334, Mar. 2017.
[12] J. J. Lih, C. F. Sung, C. H. Li, T. H. Hsiao and H. H. Lee, “Comparison of a-Si and Poly-Si for AMOLED displays,” Society for Information Display, vol. 12, no. 4, pp. 367-371, 2004.
[13] Y. K. Lee, K. M. Kim, J. I. Ryu and D. J. Choo, “A comparison between a-Si : H TFT and poly-Si TFT for a pixel in AMOLED,” Journal- Korean Physical Society, vol. 39, pp.S291-S295, 2001.
[14] Y. K. Lee, K. M. Kim, J. I. Ryu and D. J. Choo, “A comparison between a-Si : H TFT and poly-Si TFT for a pixel in AMOLED,” Journal- Korean Physical Society, vol. 39, pp.S291-S295, 2001.
[15] S. W. Lee and S. K. Joo, “Low temperature poly-si thin-film transistor fabrication by metal-induced lateral crystallization,” IEEE Electron Device Letters, vol. 17, no. 4, pp.160-162, 1996.
[16] E. Fortunato, P. Barquinha and R. Martins, “Oxide Semiconductor Thin-Film Transistors A Review of Recent Advances,” Advanced Materials, vol. 24, no. 22, pp. 2945-2986, May 2012.
[17] K. Nomura, A. Takagi, T. Kamiya, H. Ohta, M. Hirano and H. Hosono, “Amorphous oxide semiconductors for high-performance flexible thin-film transistors,” Japanese Journal of Applied Physics, vol. 45, no. 5 B, pp. 4303-4308, May 2006.
[18] T. Kamiya, K. Nomura and H. Hosono, “Present status of amorphous In-Ga-Zn-O thinfilm transistors,” Science and Technology of Advanced Materials, vol. 11, no. 4, Aug 2010.
[19] ''Ansforce,'' May 2017, http：//uigelz.ece.uiuc.edu/Projects/HPEM-ICP/index.html.
[20] J. H. Lee, J. H. Kim and M. K. Han, “A new a-Si:H TFT pixel circuit compensating the threshold voltage shift of a-Si:H TFT and OLED for active matrix OLED,” IEEE Electron Device Letters, vol. 26, no. 12, pp. 897-899, Dec 2005.
[21] A. Nathan, G. R. Chaji and S. J. Ashtiani, “Driving schemes for a-Si and LTPS AMOLED displays,” IEEE/OSA Journal of Display Technology, vol. 1, no. 2, pp. 267-277, Dec 2005.
[22] S. H. Jung, W. J. Nam and M. K. Han, “A new voltage-modulated AMOLED pixel design compensating for threshold voltage variation in Poly-Si TFTs,” IEEE Electron Device Letters, vol. 25, no. 10, pp. 690-692, Oct 2004.
[23] S. H. Jung, W. J. Nam and M. K. Han, “A new voltage-modulated AMOLED pixel design compensating for threshold voltage variation in Poly-Si TFTs,” IEEE Electron Device Letters, vol. 25, no. 10, pp. 690-692, Oct 2004.
[24] C. L. Lin, C. C. Hung, P. C. Lai and W. Y. Chang, “A New a-IGZO AMOLED Pixel Circuit Design to Improve the OLED Luminance Degradation in 3D Displays,” Society for Information Display, vol. 44, no. 1, pp. 1107-1109, Jul 2013.
[25] H. Jung, Y. Kim, Y. Kim, C. Chen, J. Kanicki and H. Lee, “a-IGZO TFT Based Pixel Circuits for AM-OLED Displays,” Society for Information Display, vol. 43, no. 1, pp.1097-1100, Jun 2012.
[26] R. M. A. Dawson , Z. Shen, D. A. Furst, S. Connor, J. Hsu, M. G. Kane, R. G. Stewart, A. Ipri, C. N. King, P. J. Green, R. T. Flegal, S. Pearson, W. A. Barrow, E. Dickey, K. Ping, S. Robinson, C. W. Tang, S. Van Slyke, F. Chen, J. Shi, M. H. Lu and J. C. Sturm, “The impact of the transient response of organic light emitting diodes on the design of active matrix OLED displays,” International Electron Devices Meeting Technical Digest, pp. 875-878, 1998.
[27] R. M. A. Dawson , Z. Shen, D. A. Furst, S. Connor, J. Hsu, M. G. Kane, R. G. Stewart, A. Ipri, C. N. King, P. J. Green, R. T. Flegal, S. Pearson, W. A. Barrow, E. Dickey, K. Ping, S. Robinson, C. W. Tang, S. Van Slyke, F. Chen, J. Shi, M. H. Lu and J. C. Sturm, “The impact of the transient response of organic light emitting diodes on the design of active matrix OLED displays,” International Electron Devices Meeting Technical Digest, pp. 875-878, 1998.
[28] G. Gu and S. R. Forrest, “Design of flat-panel displays based on organic lightemitting devices,” IEEE Journal on Selected Topics in Quantum Electronics, vol. 4, no. 1, pp. 83-99, Jan 1998.
[29] S. Ono, K. Miwa, K. Maekawa and T. Tsujimura, “VT Compensation Circuit for AMOLED Displays Composed of Two TFTs and One Capacitor,” IEEE Transactions on Electron Devices, vol. 54, no. 3, pp. 462-467, Mar 2007.
[30] C. S. Chiang, J. Kanicki and K. Takechi, “Electrical Instability of Hydrogenated Amorphous Silicon Thin-Film Transistors for Active-Matrix Liquid-Crystal Displays, “Japanese Journal of Applied Physics, vol. 37, no. 11, pp. 4704-4710, 1998.
[31] M. J. Powell, C. Van Berkel and J. R. Hughes, “Time and temperature dependence of instability mechanisms in amorphous silicon thin ‐ film transistors,” Applied Physics Letters, vol. 54, no. 14, pp. 1323-1325, Apr 1989.
[32] S. Sambandan and A. Nathan, “Equivalent Circuit Description of Threshold Voltage Shift in a-Si:H TFTs From a Probabilistic Analysis of Carrier Population Dynamics,” IEEE Transactions on Electron Devices, vol. 53, no. 9, pp. 2306-2311, Aug 2006.
[33] Y. J. Park, M. H. Jung, S. H. Park, O. Kim, “Voltage-programming-based pixel circuit to compensate for threshold voltage and mobility using natural capacitance of organic light-emitting diode”, Japanese Journal of Applied Physics, vol. 49, no. 3, pp. 03CD01, 2010.
[34] Y. C. Lin and H. P. D. Shieh, “Improvement of brightness uniformity by AC driving scheme for AMOLED display,” IEEE Electron Devices Society, vol. 25, no. 11, pp. 728-730, Nov 2004.
[35] J. P. Lee, H. S. Jeon, D. S. Moon and B. S. Bae, “Threshold voltage and ir drop compensation of an AMOLED pixel circuit without a VDD Line,” IEEE Electron Devices Society, vol. 35, no. 1, pp. 72-74, Nov 2013.
[36] C. L. Fan, M. C. Shang, W. C. Lin, H. C. Hang, K. C. Chao and B. L. Guo, “LTPS-TFT pixel circuit compensating for TFT threshold voltage shift and IR-drop on the power line for AMOLED displays,” Advances in Materials Science and Engineering, May 2012.
[37] B. Geffroy, P. le Roy and C. Prat, “Organic light-emitting diode (OLED) technology: materials, devices and display technologies,” Polymer International, vol. 55, no. 6, pp.572-582, Jun 2006.
[38] J. Shen, D. Wang, E. Langlois, W. A. Barrow, P. J. Green, C. W. Tang and J. Shi, “Degradation mechanisms in organic light emitting diodes,” Synthetic Metals, Vols. 111-112, pp. 233-236, Jun 2000.
[39] D. Zou, . M. Yahiro and T. Tsutsui, “Study on the degradation mechanism of organic light-emitting diodes (OLEDs),” Synthetic Metals, vol. 91, no. 1-3, pp. 191-193, 1997.
[40] D. Zou, . M. Yahiro and T. Tsutsui, “Study on the degradation mechanism of organic light-emitting diodes (OLEDs),” Synthetic Metals, vol. 91, no. 1-3, pp. 191-193, 1997.
[41] C. L. Lin, K. W. Chou, C. C. Hung and C. D. Tu, “Lifetime Amelioration for an AMOLED Pixel Circuit by Using a Novel AC Driving Scheme,” IEEE Transactions on Electron Devices, vol. 58, no. 8, pp. 2652-2659, Aug 2011.
[42] M. Lu, M. Hack, R. Hewitt, “Power consumption and temperature increase in large area active-matrix OLED displays”, Journal of Display Technology, vol. 4, no. 1, pp. 47-53, 2008.
[43] C. Chen, J. Kanicki, K. Abe, and H. Kumomi, “AM-OLED pixel circuits based on a-InGaZnO thin film transistors,” SID The Society for Information Display, PP. 1128–1131 2009.
[44] Y. W. Jeon, S. Kim, S. Lee, et al., “Subgap density-of-states-based amorphous oxide thin film transistor simulator (DeAOTS),” IEEE Trans. Electron Devices, Vol. 57, No. 11, pp. 2988–3000, 2010.
[45] Y. G. Mo, M. Kim, C. K. Kang, et al., “Amorphous oxide TFT backplane for large size AMOLED TVs,” SID Symposium Digest of Technical Papers, PP. 1037–1040 2010.
[46] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M.Hirano and H. Hosono, “Roomtemperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors,” Nature, vol. 432, pp. 488-492, 2004.
[47] Y. G. Mo, M. Kim, C. K. Kang, J. H. Jeong, Y. S. Park, C. G. Choi, H. D. Kim, S. S. Kim, "69.3: Amorphous oxide TFT backplane for large size AMOLED TVs", SID Symposium Digest of Technical Papers, pp. 1037-1040, 2010.
[48] C. L. Lin, W. Y. Chang, and C. C. Hung, “Compensating pixel circuit driving AMOLED display with a-IGZO TFTs, “IEEE Electron Device Letters, vol. 34, no. 9, pp. 1166–1168, Sep. 2013.
[49] Y. Kim, C. Chen, J. Kanicki, and H. Lee, “An a-InGaZnO TFT pixel circuit compensating threshold voltage and mobility variations in AMOLEDs,” Journal of Display Technology, VOL. 10, NO. 5, pp. 402-406, MAY 2014.
[50] S. J. Song, H. Nam. Chaji, and S. J. Ashtiani, “In-pixel mobility compensation scheme for AMOLED pixel circuits, “Journal of Display Technology, vol. 11, no. 2, pp. 209– 213, Feb. 2015.
[51] Y.G.Mo, M. Kim, C. K.Kang, J.H. Jeong, Y. S. Park, C.G. Choi, H. D. Kim, and S. S. Kim, “Amorphous-oxide TFT backplane for largesized AMOLED TVs,”Journal of the Society for Information Display, vol. 19, pp. 16–20, 2011.
[52] T. Tanabe, S. Amano, H. Miyake, A. Suzuki, R. Komatsu, J. Koyama, S. Yamazaki, K. Okazaki, M. Katayama, H. Matsukizono, Y. Kanzaki, and T. Matsuo, “New threshold voltage compensation pixel circuits in 13.5-inch quad full high definition OLED display of crystalline In-Ga-Zn-Oxide FETs,” SID Symposium Digest of Technical Papers, vol. 43, pp. 88–91, 2012.
[53] C. Leng; C. Liao, L. Wang, and S. Zhang, “An a-IGZO TFT pixel circuit for AMOLED with simultaneous VT compensation,”IEEE International Conference on Solid State and Integrated Circuits Technology, pp. 1–3, 2012.
[54] Y. Kim, J. Kanicki, and H. Lee, “An a-InGaZnO TFT pixel circuit compensating threshold voltage and mobility variations in AMOLEDs,” Journal of Display Technology, vol. 10, no. 5, pp. 402–406, May 2014.
[55] C Liao, “Mobility impact on compensation performance of AMOLED pixel circuit using IGZO TFTs,” Journal of Semiconductors, 40(2) 2019.
[56] D. Kim, Y. Kim, S. Lee, M. S. Kang, D. H. Kim, and H. J. Lee, “High Resolution a-IGZO TFT Pixel Circuit for Compensating Threshold Voltage Shifts and OLED Degradations,” IEEE J. Electron Devices Soc., vol. 5, pp. 372-377, Sep. 2017.
[57] C. L. Lin, P. S. Chen, P.C. Lai, T. C. Chu, M. X. Wang, and C. L. Lee, “Novel Pixel Circuit With Compensation for Normally-OFF/ON a-IGZO TFTs and OLED Luminance Degradation,” Journal of Display Technology, vol. 12, no. 12, pp. 1664-1667, Dec. 2016.
[58] R. Dawson, Z. Shen, D. A. Furest, S. Connor, J. Hsu, M. G. Kane, R. G. Stewart, A. Ipri, C. N. King, P. J. Green, R. T. Flegal, S. Pearson, C.W. Tang, S. Van Slyke, F. Chen, J. Shi,M. H. Lu, and J. C. Sturm,”The impact of the transient response of organic light emitting diodes on the design of active matrix OLED displays,” IEEE International Electron Devices Meeting, pp. 875–878, 1998.
[59] S. Forrest, P. Burrows, and M. Thompson, “The dawn of organic electronics,” IEEE Spectrum, vol. 37, no. 8, pp. 29–34, 2000.
[60] M. Stewart, R. S. Howell, L. Pires, M. K. Hatails, W. Howard, and O. Prache, “Polysilicon VGA active matrix OLED displays-technology and performance” IEEE International Electron Devices Meeting, pp. 871-874, 1998.
[61] Y. Morimoto, T. Jinno, K. Hirai, H. Ogata, T. Yamada, and K. Yoneda, “Influence of grain boundaries and intragrain defects on the performance of poly-si thin film transistors,” Journal of The Electrochemical Society, vol. 144, no. 7, 1997.
[62] A. Nathan, G. R. Chaji, and S. J. Ashtiani, “Driving scheme for a-Si and LTPS AMOLED Displays,” Journal of Display Technology, vol. 1, no. 2, pp. 267–277, Dec. 2005.
[63] K. Nomura,H. Ohta, A. Takagi, T. Kamiya,M.Hirano, and H. Hosono,”Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors,” Nature, vol. 432, pp. 488–492, 2004.
[64] T.-C. Fung, K. Abe, H. Kumomi, and J. Kanicki, “Electrical instability of RF sputter amorphous In-Ga-Zn-O thin-film transistors,” Journal of Display Technology, vol. 5, no. 12, pp. 452–461, Dec. 2009.
[65] Y. C. Kim, J. Kanicki, and H. J. Kim “An aInGaZnO TFT Pixel Circuit Compensating Threshold Voltage and Mobility Variations in AMOLEDs,” Journal of Display Technology, Vol.10, No.5, pp.402-406, May 2014.
[66] Y. J. Park, M. H. Jung, S. H. Park, O. Kim, “Voltage-programming-based pixel circuit to compensate for threshold voltage and mobility using natural capacitance of organic light-emitting diode”, Japanese Journal of Applied Physics, vol. 49, no. 3, pp. 03CD01, 2010.
[67] S.-J. Song, H. Nam, “In-Pixel Mobility Compensation Scheme for AMOLED Pixel Circuits”, Journal of Display Technology, vol. 11, no. 2, pp. 209-213, Feb. 2015.
[68] I. Nam, D.H. Woo, “Poly-Si active matrix organic light-emitting diode pixel circuit with compensation for threshold voltage and mobility variations,” Electronics Letters. 50 (13), pp.934–935, 2014.
[69] Y. Kim, J. Kanicki, and H. Lee, “An a-InGaZnO TFT pixel circuit compensating threshold voltage and mobility variations in AMOLEDs,” Journal of Display Technology, vol. 10, no. 5, pp. 402–406, May 2014.
[70] Liao, C. et al, “Mirrored OLED pixel circuit for threshold voltage and mobility compensation with IGZO TFTs,” Microelectronics Journal, 46, 923−927, 2015.
[71] Z Liao, H Lin, B Liu, M Zhang, “Mobility variation and threshold voltage shift immunized amorphous-indium-gallium-zinc-oxide pixel circuit,” IEEE International Conference on Electron Devices and Solid-State Circuits, pp 255-258, 2016.
[72] Chih-Lung Lin*, Fu-Hsing Chen, Yen-Ting Liu, Chun-Ming Lu, and Wan-Lin Wu, “New Voltage-Programmed AMOLED Pixel Circuit Employing In-Pixel Compensation Scheme for Mobility Variation,” SID Symposium Digest of Technical Papers, pp 1254–1256, 2016.