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Proceedings Paper

Role of copper phthalocyanine in multilayer organic LEDs based on small molecules
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Paper Abstract

The role of copper-phthalocyanine (CuPc) has intermediate layer between the anode and the hole-transport layer in multilayer organic light-emitting devices (OLEDs) was studied. The OLEDs consisted of CuPc, N,N'-di(naphtalene-1-yl)-N,N'-diphenyl-benzidine (NPB) as hole-transport layer and tris-(8-hydroxyquinolinato)-aluminum (Alq3) as electron-transport and emitting layer sandwiched between a high-work-function metal and a semi-transparent calcium cathode. A combinatorial approach that allows the simultaneous fabrication of 10 x 10 individual devices was used to vary the thicknesses of CuPc and NPB over a broad range from 0 to 45 nm and from 10 to 100 nm, respectively. Systematic current-voltage and impedance measurements revealed a redistribution of the internal electric field of the CuPc/NPB/Alq3 three-layer structure compared to that of the NPB/Alq3 bilayer OLED. It was demonstrated that the hole transport is mainly controlled by the internal energy barrier at the CuPc/NPB interface. The fact that CuPc strongly impedes hole injection into NPB also has a significant impact on the frequency-dependent behavior of the capacitance, especially the cutoff frequency.

Paper Details

Date Published: 3 March 2003
PDF: 8 pages
Proc. SPIE 4800, Organic Light-Emitting Materials and Devices VI, (3 March 2003); doi: 10.1117/12.457919
Show Author Affiliations
Heike Riel, IBM Zurich Research Lab. (Switzerland)
Tilman A. Beierlein, IBM Zurich Research Lab. (Switzerland)
Siegfried Karg, IBM Zurich Research Lab. (Switzerland)
Walter Riess, IBM Zurich Research Lab. (Switzerland)

Published in SPIE Proceedings Vol. 4800:
Organic Light-Emitting Materials and Devices VI
Zakya H. Kafafi; Homer Antoniadis, Editor(s)

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