Weak-microcavity organic light-emitting diodes with improved light out-coupling

We propose and demonstrate weak-microcavity organic light-emitting diode (OLED) displays with improved light-extraction and viewing-angle characteristics. A single pair of low-and high-index layers is inserted between indium tin oxide (ITO) and a glass substrate. The electroluminescent (EL) efficiencies of discrete red, green, and blue weak-microcavity OLEDs are enhanced by 56%, 107%, and 26%, respectively, with improved color purity. Moreover, full-color 128 x 160 passive-matrix bottom-emitting OLED displays are fabricated by employing low-index layers of two thicknesses. As a display, the EL efficiency of white color was 27% higher than that of a conventional OLED display. (c) 2008 Optical Society of America.