RESUMO
Oxide semiconductor thin-film transistors (TFTs) are used in the pixel array and gate driver circuits of organic light emitting diode (OLED) display panels. Long-term reliability characteristics of the TFTs are a barometer of the lifetime of OLED display panels. The long-term reliability of the driver TFTs is evaluated in a short time under high voltages and high temperature for an accelerated degradation test. If reliability parameters from the power law or stretched-exponential functions are the same for individual devices and devices in an operating panel, the lifetime of the panel can be accurately estimated. However, since compensation circuits are designed into operating panels, an environmental discrepancy exists between the accelerated test of single devices and the operation of devices in the panel. Herein, we propose a novel compensation stretched-exponential function (CSEF) model which captures the effect of the threshold voltage compensation circuit in the panel. The CSEF model not only bridges the discrepancy between individual devices and panel devices, but also provides a method to accurately and efficiently estimate the long-term lifetime of all display panels that utilize compensation circuits.
RESUMO
Drain currents as functions of the gate voltages for the thin-film transistors (TFTs) showed that their output currents had slight differential variations in the saturation region just as the output currents of the etch stopper TFTs did. The maximum difference in the threshold voltages for the In-Ga-Zn-O (a-IGZO) TFTs was as small as approximately 0.57 V. The color gamut of organic light-emitting devices (OLEDs) embedded with TFTs with a coplanar structure satisfied the digital cinema initiatives of 99%. Furthermore, the image density of large-size OLEDs embedded with TFTs with a coplanar structure was significantly enhanced in comparison with that of OLEDs embedded with conventional TFTs.
