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SDK Offers Samples of Titania Paste for Use in Solar Cell Electrode

September 16, 2003

Showa Denko K.K. (SDK) has developed titanium oxide paste that can be formed into a film at low temperature, for use in electrodes of a dye-sensitized solar cell (DSC). Samples of the new product (trade name: SP-X) are being offered.
In DSC, a flow of excited electrons, which results from the absorption of sunlight by dye, is led to electrodes made of semiconductor particles, including titanium oxide, thereby causing electromotive force (photon-to-electron conversion). Compared with conventional silicon-based solar cells, DSC is easier to fabricate and can be fabricated at lower cost.
DSC can be developed in two different directions. One is as a replacement of conventional silicon-based solar cells, using a glass substrate. The other will use flexible resin substrate for such portable goods applications as hats and umbrellas. It can also be used in blinds, tents and automobiles.
Titanium oxide particles play a key role in DSC, ensuring effective use of the flow of electrons resulting from the absorption of sunlight by dye.
Since heat treatment of titanium oxide particles at nearly 500°C is required to ensure sufficient photon-to-electron conversion, glass has been used as substrate for electrodes. However, use of a resin film substrate has been studied because it will offer advantages in terms of weight, flexibility and portability. The problem has been that a substrate made from resins allows heat treatment of titanium particles at only around 150°C, meaning that sufficient photon-to-electron conversion is not ensured.
And, in forming a titanium oxide film on a resin film substrate, coating/drying of titanium oxide paste is the most convenient process compared with such alternatives as electro-deposition (electrophoresis) and application with pressure.
SDK has therefore developed “SP-X” titanium oxide paste. This new technology enables low-temperature formation of a titanium oxide film that can be used with a resin film substrate for DSC. Specifically, the new technology has the following characteristics:

  • 1.Nano-scale control of primary particle sizes (any size between 10 and 500 nm)
  • 2.Specially designed titanium oxide structure that facilitates dye adsorption on titanium oxide particles and electron flow / electrolyte diffusion inside the titanium oxide film
  • 3.Combination of titanium oxide particles with different sizes to effectively use long-wave light
  • 4.Optimized blending of organic binders

SP-X will be produced by Showa Titanium Co., Ltd., a wholly owned subsidiary of SDK located in Toyama City, Toyama Prefecture. The company is already producing a variety of titanium oxide products for such applications as dielectric, photocatalyst, and ultraviolet shield. SDK is planning to sell ¥7 billion of titanium oxide products in 2010.
In line with the medium-term consolidated business plan named the “Sprout Project,” SDK will promote the titanium oxide business centering on the electronics and environment-related markets.

[Reference]

1. DSC structure

2. Coating on a resin substrate