An AMOLED pixel circuit for high image quality of 1000ppi mobile displays in AR and VR applications

Abstract

In this paper, an active-matrix organic light-emitting diode pixel circuit is proposed to improve the image quality of 5.87-in. mobile displays with 1000ppi resolution in augmented and virtual reality applications. The proposed pixel circuit consisting of three thin-film transistors (TFTs) and two capacitors (3T2C) employs a simultaneous emission driving method to reduce the number of TFTs and the emission current error caused by variations in threshold voltage (Vth) and subthreshold slope (SS) of the low-temperature polycrystalline silicon TFTs. Using the simultaneous emission driving method, the compensation time is increased to 90s from 6.5s achieved in the conventional six TFTs and one capacitor (6T1C) pixel circuit. Consequently, the emission current error of the proposed 3T2C pixel circuit was reduced to +/- 3 least significant bit (LSB) from +/- 12 LSB at the 32nd gray level when the variations in both the Vth and SS are +/- 4 sigma. Moreover, both the crosstalk errors due to the parasitic capacitances between the adjacent pixel circuits and due to the leakage current were achieved to be less than +/- 1 LSB over the entire gray level. Therefore, the proposed pixel circuit is very suitable for active-matrix organic light-emitting diode displays requiring high image quality.