Tokyo : Tanaka Holdings Co., Ltd. (a company of Tanaka Precious Metals), announced today 
that Tanaka Kikinzoku Kogyo K.K., which operates the Tanaka Kikinzoku Group’s manufacturing business, will begin provision of DX (Dye-X) ruthenium complex dye used in dye sensitized solar cells with the photoelectric conversion wavelength band extended to over 1,000 nanometers (a nanometer is a billionth of a meter).
- The University of Tokyo has developed a dye enabling the efficient photoelectric conversion of the long-wavelength region (near infrared light). It will be manufactured and sold by Tanaka Kikinzoku.
DX is a sensitizing dye for dye sensitized solar cells developed by a team including Hiroshi Segawa Professor of Research Center for Advanced Science and Technology at the University of Tokyo, who is a key researchers in the Cabinet Office’s Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST), and is a next-generation sensitizing dye able to efficiently absorb and perform photoelectric conversion of near infrared light(*1) that could not be absorbed by ruthenium sensitizing dyes used in the past. Tanaka Kikinzoku Kogyo received a license for DX from the University of Tokyo to jointly apply for an international patent for DX, and will manufacture and sell the product from January 2015.
- Success in extending the power generation wavelength range (spectral sensitivity range) results in realization of high current density and high conversion efficiency
The threshold on the long-wavelength side of the power generation wavelength range of existing dye sensitized solar cells was limited to 800 nanometers, and dye able to absorb near-infrared light enabling the use of long-wavelength light had to be developed. DX series dyes employ spin inversion excitation (*2) to successfully extend the long-wavelength side of the power generation wavelength range by around 200 nanometers compared to existing sensitizing dyes. As a result, the photocurrent of solar cells is improved by over 25%, and high-performance solar cells using DX series dyes are able to provide the world’s highest photocurrent for an organic solar cell at 30mA/cm2 with a high conversion efficiency of over 10.0%. DX is also suitable for generating power from outdoor light because it is able to perform photoelectric conversion of near infrared light with a longer wavelength than visible light more efficiently than existing sensitizing dyes. A tandem cell able to further increase the conversion efficiency by combining it with a dyes specifically for visible light, such as CYC-B11, is currently being developed.
- Efforts aimed at widespread adoption of dye sensitized solar cells
Dye-sensitized solar cells generate power utilizing a mechanism in which dye is applied to porous titanium oxide, absorbing light and releasing electrons to the titanium oxide. The conversion efficiency tends to be maintained even in low light, and because it is not dependent on the angle of incidence of sunlight, it is expected to be used in various applications for which previous silicon-based solar cells were unsuitable for, and is being developed as a type of next-generation solar cell offering high added value at low cost.
One important element for obtaining high conversion efficiency in dye sensitized solar cells is the structure of the dye that absorbs the light, and much R&D is currently being carried out on ruthenium complex dye as a stable dye with high performance.
Moving forward, Tanaka Kikinzoku Kogyo and the University of Tokyo will proceed with development aimed at improving the efficiency and durability of DX, such as the development of a tandem cell combining DX with a conventional dye for absorbing visible light. Tanaka Kikinzoku Kogyo aims for annual sales of 200 million yen through supplying DX.
As a producer of precious metals, Tanaka Kikinzoku Kogyo is engaged in efforts to reduce manufacturing costs aimed at practical application and widespread use, such as stable procurement of the ruthenium used as a material in the dye, development of high-yield manufacturing processes, and recycling for the effective use of ruthenium.