Development of Dye-sensitized Solar Modules for Artistic Designs
Kazuo Higuchi, Naohiko Katoand dark-green DSCs4) (Fig. 3). This object had
been exhibited in the "energy garden" in theapproach area of the TOYOTA Group Pavilion in
EXPO 2005 (Fig. 4). This particular module wasdeveloped to symbolize the fact that DSCs are basedon a mechanism inspired by photosynthesis inplants. The dependence of the cell properties on thedyes and the treatment of the electrodes has beenclarified and optimized. As a demonstration of thegeneration of electricity, butterflies (which were theprinciple motif of the main show at the TOYOTAGroup Pavilion) flutter and stop using the electricity
generated by this plant under intermittent lighting
conditions. The freedom of shape and color, and thetransparency demonstrated by this object suggest avariety of future applications for this type of DSC.
Acknowledgements
We appreciate the cooperation of IMRA-EUROPE
S.A.S., AISIN COSMOS R&D CO., LTD. and
TOYOTA Motor Corp., during this development.

Dye-sensitized solar cells (DSCs) consisting ofnanocrystalline TiO2, dyestuff and electrolyte are
attracting general attention as less expensive
photovoltaic (PV) modules for next-generation PVs.
We have developed two types of DSC modules tomeet different artistic designs, and we exhibitedthem during the period of Aichi EXPO 2005,
preceded by an outdoor performance test of a large1, 2)
in collaboration with AISIN SEIKI
scale moduleCo., Ltd.
The first consists of wall-integrated 2.25 m 2.5 m
3)solar panels based on DSCs (Fig. 1) that were2developed for a 22.5 m facade at the TOYOTADream House: "PAPI" (Fig. 2). To produce theornamental features requested by the architect,reflectors of rugged aluminum plates were employedon the backsides of the transparent DSCs, together
with a newly-developed frameless structure. On
sunny days, the DSC panels have a magenta granitic
or marbled appearance, whereas on cloudy days theytake on a dark raspberry color and fade into thebackground, so that the outer glass shields clearlyreflect the scenery of the surrounding garden. The
electricity generated by the DSC panels is
continuously monitored by AISIN SEIKI Co., Ltd.,Kariya, wirelessly via a cellular phone communication system. It was revealed that the DSC panels
gave a faster rise in electricity generation than aconventional Si solar cell in the morning, and aslower fall in the afternoon, mainly due to adifferent dependence of electricity generationon the solar insolation angle.
The second is an art object of a plant withtransparent leaves of yellow, red, light-green

Fig. 2(a)References
1) Toyoda, T., et al. : J. Photochem. and Photobiol. A,164(2004), 203
2) Higuchi, K., et al. : Papers of EXPO WCWRF 2005,
No. 2013(2005), (CD-ROM)
3) Doi, S., et al. : Papers of EXPO WCWRF 2005,No. 2014(2005), (CD-ROM)
4) Nakajima, J., et al. : Papers of EXPO WCWRF 2005,
No. 2015(2005), (CD-ROM)(Report received on Jan. 17, 2006)

The appearance of PAPI withfour wall-integrated DSC panels.

(b)Fig. 4
Fig. 1(a) Transparent dye-sensitized solar cells(240 mm 240 mm). (b) A unit module
composed of 12 DSCs and a reflector ofrugged aluminum plates (515 mm 773mm).

Fig. 3

Leaf-shaped transparent
DSCs with four colors.

Art object of a plant withleaves of DSCs coloredyellow, red, light-green
and dark-green, exhibitedat the TOYOTA Group
Pavilion in EXPO 2005.

This news is reported on R&D Review of Toyota CRDL Vol.41 No.1.
Copyright (C) 2006 Toyota Central R&D Labs., Inc.