title: Optimizing the charge balance of fluorescent organic light-emitting devices to achieve high external quantum efficiency beyond the conventional upper limit.
abstract: The external quantum efficiencies (EQEs) of fluorescent light emitting devices are drastically improved by optimizing the charge balance. When N,N'-di(naphthalene-1-yl)- N,N'-diphenylbenzidine (NPD) is used as a hole-transporting layer (HTL) and Alq(3)  as an electron-transporting layer (ETL) with the green dopant 2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl)quinolizino-[9,9a,1gh]coumarin (C545T), the EQE is observed to be approximately 3%. However, when the HTL and ETL materials are optimized, a 7.5% external quantum efficiency (EQE) in a green-emitting device and an 8.2% EQE in a blue-emitting device are achieved at 100 cd m(-2) .
authors.affiliation: Department of Organic Device Engineering, Research Center for Organic Electronics, Yamagata University, Yonezawa, Japan. pu@yz.yamagata-u.ac.jp
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Pu
authors.forename: Go
authors.initials: G
authors.lastname: Nakata
authors.forename: Fumiya
authors.initials: F
authors.lastname: Satoh
authors.forename: Hisahiro
authors.initials: H
authors.lastname: Sasabe
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yokoyama
authors.forename: Junji
authors.initials: J
authors.lastname: Kido
mesh_terms: D001560:Benzidines / Q000737:chemistry; D003374:Coumarins / Q000737:chemistry; D004583:Electrons; D004867:Equipment Design; D005453:Fluorescence; D008029:Lighting / Q000295:instrumentation*; D009281:Naphthalenes / Q000737:chemistry
chemical_list: D001560:Benzidines; D003374:Coumarins; D009281:Naphthalenes; C030123:coumarin