Abstract
A new low-frame-rate active-matrix organic light-emitting diode (AMOLED) pixel circuit with low-temperature poly-Si and oxide (LTPO) thin-film transistors (TFTs) for portable displays with high pixel density is reported. The proposed pixel circuit has the excellent ability to compensate for the threshold voltage variation of the driving TFT (ΔVTH_DTFT). By the results of simulation based on a fabricated LTPS TFT and a-IZTO TFT, we found that the error rates of the OLED current were all lower than 2.71% over the range of input data voltages when ΔVTH_DTFT = ±0.33 V, and a low frame rate of 1 Hz could be achieved with no flicker phenomenon. Moreover, with only one capacitor and two signal lines in the pixel circuit, a high pixel density and narrow bezel are expected to be realized. We revealed that the proposed 7T1C pixel circuit with low driving voltage and low frame rate is suitable for portable displays.
Highlights
Active-matrix organic light-emitting diode (AMOLED) displays have been commonly used in high-end portable displays, because they exhibit various advantages, such as shorter response time, higher contrast ratio, and thinner thickness compared with conventional liquid crystal displays (LCDs) [1,2]
This study proposed a low-power-consumption pixel circuit containing two signal lines, and utilizing low-temperature poly-Si and oxide (LTPO) thin-film transistors (TFTs) to compensate for the threshold voltage variation of the driving TFTs (∆VTH_DTFT )
A new low driving voltage (5 V) compensation pixel circuit using LTPO TFT structure was presented for use in high-pixel-density portable active-matrix organic light-emitting diode (AMOLED) displays
Summary
Active-matrix organic light-emitting diode (AMOLED) displays have been commonly used in high-end portable displays, because they exhibit various advantages, such as shorter response time, higher contrast ratio, and thinner thickness compared with conventional liquid crystal displays (LCDs) [1,2]. The backplane technology of low-temperature poly-Si (LTPS) thin-film transistors (TFTs) are widely used in pixel circuits for portable AMOLED displays, since it has excellent current capability [5,6,7]. It has some demerits, such as nonuniformity of threshold voltage (VTH ) and high manufacturing costs [8,9]. This study proposed a low-power-consumption pixel circuit containing two signal lines, and utilizing LTPO TFTs to compensate for the threshold voltage variation of the driving TFTs (∆VTH_DTFT ). With low driving voltage of 5 V, and the ability to be driven at a low frame rate of 1 Hz, we believe that the proposed 7T1C pixel circuit with two signal lines is suitable for portable applications
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