27 February 2002 Photoemission studies of organic phosphors doped in electron and hole transport hosts
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Abstract
Using a combination of ultraviolet and x-ray photoelectron spectroscopies (UPS, XPS), we have studied the relative energy level alignment of two phosphorescent guest molecules, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum (PtOEP) and tris(2-phenylpyridine)iridium (Ir(ppy)3), doped in an electron transport host, tris(8-hydroxyquinolinato) aluminum (III) (Alq3), and in a hole transport host, 4,4'-bis(carbazol-9-yl)biphenyl (CBP). In each of the guest-host systems, we find that the vacuum levels of the guest and the host molecules align, and that the position of the highest occupied molecular orbital (HOMO) of the phosphorescent guest is independent of the guest molecule concentration (0.8 - 56% by mass) in the composite films. These results are used to shed light on possible electroluminescence mechanism(s) in the emissive layer of an organic light-emitting device utilizing the studied guest-host structures.
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Antti Johannes Maekinen, Ian G. Hill, Zakya H. Kafafi, "Photoemission studies of organic phosphors doped in electron and hole transport hosts", Proc. SPIE 4464, Organic Light-Emitting Materials and Devices V, (27 February 2002); doi: 10.1117/12.457471; https://doi.org/10.1117/12.457471
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