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Journal of Display Technology

Journal of Display Technology


  • Vol. 2, Iss. 4 — Dec. 1, 2006
  • pp: 347–358

A Stable Voltage-Programmed Pixel Circuit for a-Si:H AMOLED Displays

G. Reza Chaji and Arokia Nathan

Journal of Display Technology, Vol. 2, Issue 4, pp. 347-358 (2006)

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Hydrogenated amorphous silicon (a-Si:H) active matrix organic light-emitting diode (AMOLED) displays are attractive given the potentially low manufacturing cost and ultimately low-temperature fabrication enabling using flexible substrates. Although the conventional two thin-film transistor (2-TFT) AMOLED voltage-programmed pixel circuit (VPPC) can provide high resolution and high yield, the 2-TFT VPPC is prone to image retention over time due to shift in the threshold voltage (VT-shift) of a-Si:H TFTs. This paper presents a new driving scheme that not only preserves the simplicity of the 2-TFT VPPC, but also demonstrates high uniformity. Experimental results indicate that the current drop in the new driving scheme is less than 11% after 15 days of operation whereas it is over 50% for the conventional driving scheme. Moreover, the new driving scheme is less sensitive to temperature variations due to an internal feedback mechanism. After a 70% change in the temperature, the current in the conventional driving scheme increases by as much as 300%. However, the current in the driving scheme presented here is approximately constant.

© 2006 IEEE

G. Reza Chaji and Arokia Nathan, "A Stable Voltage-Programmed Pixel Circuit for a-Si:H AMOLED Displays," J. Display Technol. 2, 347-358 (2006)

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