Graded-host phosphorescent light-emitting diodes with high efficiency and reduced roll-off

• Main Authors: Liu, S. W., Sun, Xiaowei, Demir, Hilmi Volkan
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: https://hdl.handle.net/10356/96009; http://hdl.handle.net/10220/10060
• Institution: Nanyang Technological University

We demonstrated graded-host phosphorescent organic light-emitting diodes with high efficiency and reduced efficiency roll-off. The emissive layer of the graded host device consists of both electron and hole transport type hosts, 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBI) and 4,4′,4′′-tris(N-carbazolyl)triphenylamine, respectively, with graded composition, and the phosphorescent red emitter bis(2-phenylquinoline) (acetylacetonate) iridium(III), which was uniformly doped into the graded host matrix. The graded host device shows improved quantum efficiency and power efficiency with significantly reduced efficiency roll-off as compared to the unipolar-host and double layer heterojunction host devices.