Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

Fig. 4. Schematic illustration of a LSC based on oriented dye-zeolite crystals. The channels of the
disc-shaped crystals run perpendicular to the face of the LSC. The axial cut shows the double
cone distribution of the electronic transition dipole moments for two different dyes. The blue
double cones represent the donor molecules (absorbers, large cone angle), whereas the
green double cones indicate acceptor molecules (emitters, small cone angle). The red cone
illustrates an escape cone originating at an emitter located close to a channel entrance.
Results
During the initial 7 months of the project, we mainly focused on preparative issues. A first round of
screening for suitable dye molecules has been completed. Experiments to find the optimum conditions
for the incorporation of these dyes into zeolite L have started and are ongoing. First prototypes were
prepared by sandwiching a thin dye(1)-dye(2)-zeolite-PMMA layer between two ordinary glass plates.
The thickness of the layer can be varied between 0.5 and 20 µm. The transparency of the layers was
investigated as a function of the zeolite/polymer ratio. Outdoor stability tests revealed the importance
of sealing the zeolite channels. New prototypes now include two types of donor molecules and cationic
acceptor molecules at the channel entrances. The latter should prevent leaching of the neutral donor
molecules. We have furthermore extended the preparation of oriented zeolite L layers to larger surfaces
(100 cm 2 ).
An important step in terms of the detailed characterization of the prototypes was the development of
an experimental setup for measuring the luminescence spectrum emitted at the edge of the LSC. This
will allow us to study the photon-transport properties of the LSCs and to correlate the photocurrent
response of edge-mounted solar cells with the edge-emitted luminescence spectrum.
Collaborations
This project is a collaboration between the research group of Dr. Dominik Brühwiler (University of
Zurich), Prof. Dr. Gion Calzaferri (University of Berne), and Dr. Andreas Kunzmann (Optical Additives
GmbH). The current project staff at the University of Zurich includes two postdoctoral researchers (Dr.
Christophe Bauer and Dr. Igor Dolamic). Methods for high volume production are developed in
collaboration with Clariant.
Evaluation 2008 and Outlook 2009
The start of the project was successful. Results obtained with our first (non-optimized) prototypes are
promising. Research activities in 2009 will focus on the following issues:
� Optimization of the preparative steps. This includes: (1) Increase of the dye loading (leading to
more efficient energy transfer and higher optical density); (2) Improving the deposition of zeolite
layers on large areas; (3) Increasing the zeolite/polymer ratio without causing scattering within
the zeolite-polymer layer; (4) Stabilization of the dye-zeolite materials by channel sealing.
� Quantitative measurement of efficiencies
� Further evaluation of the stability under outdoor conditions
� Theoretical modeling
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Luminescent concentrators based on inorganic/organic nanomaterials, D. Brühwiler, University of Zurich
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