4 November 2002 Organic light-emitting devices based upon divalent osmium complexes: II. Design, fabrication, and characterization of osmium nanoscale devices
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Abstract
Efficient red electrophosphorescence was achieved from double-layer light emitting devices using osmium (Os) complex doped blends of either poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PVK:PBD), or poly(vinyl naphthalene) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PVN:PBD) as the emitting layer. Blending PVN with PBD greatly suppresses the electromer emission of PVN. The PVN:PBD blend emanates a short wavelength EL emission peaking at around 375 nm, which well overlaps with the absorption spectra of the Os complexes and ensures very efficient energy transfer to the Os complex dopants. PVK:PBD has and EL emission around 450 nm which does not overlap the absorption bands of the osmium complexes as well and produces devices of lower efficiency, but PVK is a better transport layer and produces brighter devices. The best external quantum efficiency of the double-layer devices was 2.2%, with a photometric efficiency of 1.9 cd/A. The brightest device achieved was 1,400 cd/m2.
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Brenden Carlson, Xuezhong Jiang, Alex K.Y. Jen, Larry Raymond Dalton, "Organic light-emitting devices based upon divalent osmium complexes: II. Design, fabrication, and characterization of osmium nanoscale devices", Proc. SPIE 4809, Nanoscale Optics and Applications, (4 November 2002); doi: 10.1117/12.453782; https://doi.org/10.1117/12.453782
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