A New AMOLED Pixel Circuit With Pulsed Drive and Reverse Bias to Alleviate OLED Degradation

Abstract

Abstract-This paper proposes a new pixel circuit for an active matrix organic light-emitting diode (OLED) display, which consists of five thin-film transistors (TFTs) and one capacitor. This circuit develops techniques of pulsed drive and reverse bias to achieve desired emitted brightness levels and elongate OLED life times, respectively. A current mirror is also adopted in the circuit to minimize emission nonuniformity of the OLED panel. The required input data voltages for varied displayed gray levels are calculated based on analytically known TFT and OLED models and the designed circuit architecture. The designed pixel circuit is simulated with realistic TFT models for validating expected performance to realize 256 gray levels and minimizing nonuniformity. The designed circuit is implemented in a 2.4-in quarter video graphics array panel, which shows favorable performance for minimizing display nonuniformity and alleviating OLED degradation. In addition, a closeness is clearly observed among analytical predictions, simulations, and experimental measurements.Index Terms-Active matrix organic light-emitting diode (AMOLED), OLED degradation, pulsed drive, reverse bias, thinfilm transistors (TFTs), threshold compensation.

Lifetime Extension Method for Active Matrix Organic Light-Emitting Diode Displays Using a Modified Stretched Exponential Decay Model

“…I N ACTIVE-MATRIX organic light-emitting diode (AMOLED) display, the analog driving that uses a current source in each pixel [1]- [3] has a problem involving variation in pixel luminance caused by a variation in the electrical characteristics of backplane thin film transistors (TFTs). To reduce the variation in pixel luminance, a compensation circuit is included in each pixel; however, this reduces the resolution and yield of AMOLED panels.…”

A New 4T0.5C AMOLED Pixel Circuit With Reverse Bias to Alleviate OLED Degradation

“…Panel nonuniformity is improved with the advances in TFT fabrication processing and developed compensation methods [1]- [3]. In [1] and [2], a self-compensation pixel circuit was designed, but it occupied the layout area of six transistors and one capacitor. Other researchers in [3] proposed the external compensation system to remedy drawbacks of panel nonuniformity without extra TFTs in a pixel circuit, which is the future design trend for high-resolution AMOLED displays.…”

“…Some other studies imposed reverse biases on an OLED component in the nonemission period for alleviating OLED lifetime degradation [6], [7]. However, as realizing the designs in [1], [2], and [5], for current compensation and degradation alleviation, more circuit components are required. In this way, the pixel size is increased, then decreasing significantly the resolution of the OLED display.…”

An Accurate and Fast Current-Biased Voltage-Programmed AMOLED Pixel Circuit With OLED Biased in AC Mode

“…A number of the AC driving schemes have been thus proposed to minimize the OLED degradation [17]- [19]. However, among those schemes, neither can the V TH variation of driving TFT be compensated [17]; nor can the reverse-biased time of OLED be long enough [14], [15], [17] for suppressing the OLED deterioration effectively [18].…”

“…However, among those schemes, neither can the V TH variation of driving TFT be compensated [17]; nor can the reverse-biased time of OLED be long enough [14], [15], [17] for suppressing the OLED deterioration effectively [18]. Moreover, an additional TFT is used for generating the reverse-bias voltage [19].…”