title: Performance improvement of green phosphorescent organic light emitting diodes with partial bulk heterojunctioned emitting layer.
abstract: Green phosphorescent organic light emitting diodes (PHOLEDs) were developed using a mixed layer system. They were fabricated with 4,4'-N,N'-dicarbazolyl-biphenyl (CBP) and typical charge transporting materials, which are 4,4'-bis[N-(naphthyl)-N-phenylamino]biphenyl (NPB) as a hole transporting material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) as an electron transporting material, mixed at each interface in a stacked organic layer to reduce the hole injection barrier and extend the recombination zone. We introduced a mixed layer for the hole transporting layer side, the electron transporting layer side, and on both sides to make a bulk heterojunction. This reduced the driving voltage, and the luminous efficiency (LE) was increased to 500 cd/m2. The optimized device showed a maximum LE of 59.87 cd/A and a maximum external quantum efficiency of 17.52%.
authors.forename: Hyung Jin
authors.initials: HJ
authors.lastname: Yang
authors.forename: Ho Won
authors.initials: HW
authors.lastname: Lee
authors.forename: Seok Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Dong Hyung
authors.initials: DH
authors.lastname: Lee
authors.forename: Ja Ryong
authors.initials: JR
authors.lastname: Koo
authors.forename: Jhin
authors.initials: J
authors.lastname: Yeong
authors.forename: Seung Soo
authors.initials: SS
authors.lastname: Yoon
authors.forename: Young Kwan
authors.initials: YK
authors.lastname: Kim
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D004867:Equipment Design; D049408:Luminescent Agents / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D012666:Semiconductors
chemical_list: D001713:Biphenyl Compounds; D049408:Luminescent Agents