Two cell architectures based on buried nano-electrodes are under investigation.

One electrode of the asymmetric set-up is realised as a comb-like structure of verti­cal electrodes and one planar counter elec­trode. The proof of principle was made and first experimental results have been pre­sented recently [9]. On the basis of the same acrylic substrate, an interdigital nano­electrode configuration can be realised.

The dimensions of the acrylic microstruc­ture are a period of the lamellas of 720nm, a depth of approximately 400nm and a width of the cavities of 400nm. The vertical metal electrodes are made by evaporation of the lamellae under a certain angle in such a

way that only the vertical regions and necessarily the tips of the structure are coated. Two electrodes can be realised by oblique evaporation of different metals. The proper separa­tion of the two electrodes is challenging from an technological point of view (figure 7).This
is done by a lift-off procedure. Once the separation is successful, there is no danger in creating shunts as the active polymer fills the cavities in the final step (figure 8).In con­trast to the planar solar cell architecture based on an ITO-substrate, both electrodes are deposited prior application of the photo active film.

This can be of an advantage for device preparation. The interface formation is an important issue. Suitable contacts with high selectivity are under investigation. As the dimensions of these structures are in the range of the wavelength of the light, near field optics play an important role. Strong interactions of the light in terms of high ab­sorption in TM-polarisation are observed.

Besides the application for solar cells, the concept of vertical interdigital nano­electrodes with distances down to 200nm offers a wide range of different applications like sensors or OLEDs.

Acknowledgements

We would like to thank Philippe Lalanne from Laboratoire Charles Fabry de L’Institut d’Optique, Orsay Cedex, France for the sim­ulation tool, J. C.Hummelen from University of Groningen for the delivery of the chemical components, Harald Hoppe from University of Linz for the determination of the optical constants and Thomas Schaller from Institut fQr Mikroverfahrenstechnik Forschungszen- trum Karlsruhe for the delivery of the microprism masterstructure.