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Thin Film Encapsulated Transparent Organic Light Emitting Diodes

Published online by Cambridge University Press:  01 February 2011

Cristina Tanase
Affiliation:
[email protected], Philips Research, Research, High Tech Campus, Eidhoven, 5656 AE, Netherlands
Peter van de Weijer
Affiliation:
[email protected], Philips Research, Eindhoven, 5656 AE, Netherlands
Herbert Lifka
Affiliation:
[email protected], Philips Research, Eindhoven, 5656 AE, Netherlands
Gerard Rietjens
Affiliation:
[email protected], Philips Research, Eindhoven, 5656 AE, Netherlands
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Abstract

Highly transparent OLEDs are very attractive for lighting and light beautification applications. While the transparent anode is based on transparent ITO, the transparent cathode is based on a 3-layer approach: (semi)transparent electron injection layer that is a low work function metal, electrically transparent conductor used in order to limit the voltage drop across the OLED area, and overcoat to tune the optical properties without influencing the electrical properties. Transparent encapsulation based on thin film technology is used in order to protect devices from ambient exposure. Using this approach large area (50 cm2) transparent organic light-emitting device having 75% transparency in the off state is demonstrated. The efficiency of the transparent OLED is comparable with that of bottom emission OLED. It is demonstrated that by tuning the thickness and optical properties of both the cathode and the encapsulation the amount of light emitted through the anode and the cathode can be varied while the total amount of light emitted by the OLED remains the same. Moreover device optimization based on optical thin film calculations has been performed such that no angular dependence of emitted light is present both on anode and cathode side.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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