title: Exciplex-Forming Co-Host-Based Red Phosphorescent Organic Light-Emitting Diodes with Long Operational Stability and High Efficiency.
abstract: The use of exciplex forming cohosts and phosphors incredibly boosts the efficiency of organic light-emitting diodes (OLEDs) by providing a barrier-free charge injection into an emitting layer and a broad recombination zone. However, most of the efficient OLEDs based on the exciplex forming cohosts has suffered from the short operational lifetime. Here, we demonstrated phosphorescent OLEDs (PhOLEDs) having both high efficiency and long lifetime by using a new exciplex forming cohost composed of N,N'-diphenyl-N,N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) and (1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl))tris(diphenylphosphine oxide) (PO-T2T). The red-emitting PhOLEDs using the exciplex forming cohost achieved a maximum external quantum efficiency (EQE) of 34.1% and power efficiency of 62.2 lm W1-with low operating voltages and low efficiency roll-offs. More importantly, the device demonstrated a long lifetime around 2249 h from 1000 cd m-2to 900 cd m-2(LT90) under a continuous flow of constant current. The efficiencies of the devices are the highest for red OLEDs with an LT90> 1000 h.
authors.affiliation: Department of Materials Science and Engineering and §Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
authors.forename: Jeong-Hwan
authors.identifier: http://orcid.org/0000-0002-2276-4912
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering and §Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Shin
authors.affiliation: Department of Materials Science and Engineering and §Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
authors.forename: Jae-Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering and §Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
authors.forename: Kwon-Hyeon
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering and §Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
authors.forename: Jang-Joo
authors.identifier: http://orcid.org/0000-0003-4926-2346
authors.initials: JJ
authors.lastname: Kim
keywords: exciplex-forming cohost; high efficiency; lifetime; phosphine oxide derivatives; red phosphorescent OLEDs