I. Introduction
Since C.W. Tang and S.A. Vanslyke of Kodak proposed an OLED scheme in 1987 [1], OLED technology became one of the popular fields of information displays in the recent decade. The OLED has unique characteristics, including self-emission, lightness, thinness, fast electronic response and a wide viewing angle [2]–[4]. Thus, the OLED panel can display any kind of real-time video without distorting colors or limiting the viewing angle. Due to its advantageous properties, the OLED panel could be the trend of next generation in information display.