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Title: Electronic structure of the polymer-cathode interface of an organic electroluminescent device investigated using operando hard x-ray photoelectron spectroscopy

The electronic structure of a polymer-cathode interface of an operating organic light-emitting diode (OLED) was directly investigated using hard X-ray photoelectron spectroscopy (HAXPES). The potential distribution profile of the light-emitting copolymer layer as a function of the depth under the Al/Ba cathode layer in the OLED depended on the bias voltage. We found that band bending occurred in the copolymer of 9,9-dioctylfluorene (50%) and N-(4-(2-butyl)-phenyl)diphenylamine (F8-PFB) layer near the cathode at 0 V bias, while a linear potential distribution formed in the F8-PFB when a bias voltage was applied to the OLED. Direct observation of the built-in potential and that band bending formed in the F8-PFB layer in the operating OLED suggested that charges moved in the F8-PFB layer before electron injection from the cathode.
Authors:
; ;  [1] ;  [2] ; ; ;  [3]
  1. Sumitomo Chemical Co., Ltd., Advanced Materials Research Laboratory, 6 Kitahara, Tsukuba, Ibaraki 300-3294 (Japan)
  2. Sumitomo Chemical Co., Ltd., Tsukuba Material Development Laboratory, 6 Kitahara, Tsukuba, Ibaraki 300-3294 (Japan)
  3. National Institute for Materials Science, Synchrotron X-ray Station at SPring-8, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)
Publication Date:
OSTI Identifier:
22494807
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CATHODES; COPOLYMERS; ELECTRIC POTENTIAL; ELECTROLUMINESCENCE; ELECTRON BEAM INJECTION; ELECTRONIC STRUCTURE; FLUORENE; HARD X RADIATION; LIGHT EMITTING DIODES; PHOTOELECTRON SPECTROSCOPY