title: Tenfold increase in the lifetime of blue phosphorescent organic light-emitting diodes.
abstract: Organic light-emitting diodes are a major driving force of the current information display revolution due to their low power consumption and potentially long operational lifetime. Although electrophosphorescent organic emitters have significantly lower power consumption than fluorescent emitters, the short lifetime of electrophosphorescent blue devices has prevented their application in displays for more than a decade. Here, we demonstrate a novel blue electrophosphorescent device with a graded dopant concentration profile in a broadened emissive layer, leading to a lower exciton density compared with a conventional device. Thus, triplet-polaron annihilation that leads to long-term luminescent degradation is suppressed, resulting in a more than threefold lifetime improvement. When this strategy is applied to a two-unit stacked device, we demonstrate a lifetime of 616±10 h (time to 80% of the 1,000 cd m(-2) initial luminance) with chromaticity coordinates of [0.15, 0.29], representing a tenfold lifetime improvement over a conventional blue electrophosphorescent device.
authors.affiliation: Department of Physics, University of Michigan, 2238 EECS, Ann Arbor, Michigan 48109, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, 2238 EECS, Ann Arbor, Michigan 48109, USA.
authors.forename: Jaesang
authors.initials: J
authors.lastname: Lee
authors.affiliation: 1] Department of Physics, University of Michigan, 2238 EECS, Ann Arbor, Michigan 48109, USA [2] Department of Electrical Engineering and Computer Science, University of Michigan, 2238 EECS, Ann Arbor, Michigan 48109, USA [3] Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Forrest