title: High-external-quantum-efficiency organic light-emitting devices.
abstract: 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 ?(e), consistent with measurements. We demonstrate a shaped substrate that increases ?(e) 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 ?(e) 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.
authors.forename: G
authors.initials: G
authors.lastname: Gu
authors.forename: D Z
authors.initials: DZ
authors.lastname: Garbuzov
authors.forename: P E
authors.initials: PE
authors.lastname: Burrows
authors.forename: S
authors.initials: S
authors.lastname: Venkatesh
authors.forename: S R
authors.initials: SR
authors.lastname: Forrest
authors.forename: M E
authors.initials: ME
authors.lastname: Thompson