We study the internal and external quantum efficiencies of vacuum-deposited organic light-emitting devices (OLED’s). The internal quantum efficiency of OLED’s based on tris-(8-hydroxyquinoline) aluminum is calculated to be 5.7 times the observed external quantum efficiency ?<sub>e</sub>, consistent with measurements. We demonstrate a shaped substrate that increases ?<sub>e</sub> by a factor of 1.9±0.2 over similar OLED’s fabricated upon flat glass substrates and leads to a 100%-emissive aperture, i.e., the emitting area completely occupies the display area even in the presence of metal interconnects. We also discuss a substrate structure that increases ?<sub>e</sub> by an additional factor of 2. The high device efficiencies are promising for developing OLED-based displays with extremely low power consumption and increased operational lifetime.
© 1997 Optical Society of AmericaPDF Article