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Proceedings Paper

White organic light-emitting diodes with ultra-thin mixed emitting layer
Author(s): T. Jeon; S. Forget; S. Chenais; B. Geffroy; D. Tondelier; Y. Bonnassieux; E. Ishow
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Paper Abstract

White light can be obtained from Organic Light Emitting Diodes by mixing three primary colors, (i.e. red, green and blue) or two complementary colors in the emissive layer. In order to improve the efficiency and stability of the devices, a host-guest system is generally used as an emitting layer. However, the color balance to obtain white light is difficult to control and optimize because the spectrum is very sensitive to doping concentration (especially when a small amount of material is used). We use here an ultra-thin mixed emitting layer (UML) deposited by thermal evaporation to fabricate white organic light emitting diodes (WOLEDs) without co-evaporation. The UML was inserted in the hole-transporting layer consisting of 4, 4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB) instead of using a conventional doping process. The UML was formed from a single evaporation boat containing a mixture of two dipolar starbust triarylamine molecules (fvin and fcho) presenting very similar structures and thermal properties and emitting in complementary spectral regions (orange and blue respectively) and mixed according to their weight ratio. The composition of the UML specifically allows for fine tuning of the emission color despite its very thin thickness down to 1 nm. Competitive energy transfer processes from fcho and the host interface toward fvin are key parameters to control the relative intensity between red and blue emission. White light with very good CIE 1931 color coordinate (0.34, 0.34) was obtained by simply adjusting the UML film composition.

Paper Details

Date Published: 17 February 2012
PDF: 7 pages
Proc. SPIE 8258, Organic Photonic Materials and Devices XIV, 82580G (17 February 2012); doi: 10.1117/12.908156
Show Author Affiliations
T. Jeon, Ecole Polytechnique, CNRS (France)
S. Forget, Univ. Paris 13, CNRS (France)
S. Chenais, Univ. Paris 13, CNRS (France)
B. Geffroy, Ecole Polytechnique, CNRS (France)
CEA-Saclay (France)
D. Tondelier, Ecole Polytechnique, CNRS (France)
Y. Bonnassieux, Ecole Polytechnique, CNRS (France)
E. Ishow, École Normale Supérieure de Cachan, CNRS (France)

Published in SPIE Proceedings Vol. 8258:
Organic Photonic Materials and Devices XIV
Christopher Tabor; François Kajzar; Toshikuni Kaino; Yasuhiro Koike, Editor(s)

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