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A new 4T0.5C circuit is proposed to achieve a highresolution active-matrix organic light-emitting diode (OLED) display with the capability of alleviating OLED degradation, while the panel nonuniformity is compensated by an already-proposed system. The designed circuit is built on two adjacent pixels with eight transistors and one capacitor, thus equivalently as a 4T0.5C pixel circuit in occupied layout area. In this circuit, a single storage capacitor is shared by the two adjacent pixels to minimize the entire layout area. The minimized pixel size is compatible to a conventional 2T1C pixel circuit. Along with this 4T0.5C circuit, a new alternative drive scheme is developed to address the panel. The scheme offers the function of automatic reverse biasing on OLEDs to alleviate degradation. The designed circuit is fabricated, and the performance of OLED degradation is successfully validated.Index Terms-Active-matrix organic light-emitting diode (AMOLED), degradation, reverse bias.

No abstract

Organic light-emitting diodes (OLEDs) have drawn much attention in areas of displays and varied illumination devices due to multiple advantages, such as high brightness, high efficiency, wide viewing angle, and simple structure. However, the long-time degradation of OLED emission is a serious drawback. This degradation was investigated by past works, which pointed out that the degradation was induced by high-density currents through OLED component under the long-time operation [1][2]. Proposed by a past work [3], different reverse biases was imposed on OLED components in display frames to alleviate the long-time degradation on OLEDs. Most recently, along with the reverse bias, new pixel circuits [4][5] for AMOLED displays are designed to alleviate OLED degradation, thus successfully extending OLED life time. However, since emission luminances in different frame times during AMOLED displaying differs significantly for displaying varied images, the OLED degradation evolves in a highly unpredictable fashion. In this study, based on valid theories, the voltage across the OLED is first used as indicator for OLED degradation. Then the relation between the level of OLED degradation, in terms of OLED’s cross voltage, and the history of imposing reverse biases are precisely modeled. With the model, the degradation of the OLED under reverse bias to extend lifetime can be successfully predicted. Based on this model, engineers can then optimize the applied reverse bias on OLEDs to maximize the OLED lifetime for varied display requirement.