16 February 2009 AIST

Researchers Develop High-Performance Organic-Dye-Sensitized Solar Cell

Kohjiro Hara and Nagatoshi Koumura, Research Scientists at AIST, have developed a high-performance dye-sensitized solar cell (DSSC) based on organic dye as part of the Grants-in-Aid Program for Scientific Research led by the New Energy and Industrial Development Organization (budget: about 5 billion yen).

This technology may provide a solution to both the high manufacturing cost of the currently predominant silicon solar cell and the unstable supply of high-purity silicon. It is positioned as an innovative photovoltaic generation technology under the 2008 Technology Strategy Map by METI and is expected to be fully commercialized and significantly reduce the cost of producing solar cells.

Figure 1. Organic-dye-sensitized solar cell prototype        Figure. 2  Molecular structrure of MK-2

Ruthenium complexes contained in conventional DSSCs are not used in the new solar cell, thus meeting the requirement for conserving this rare metal. In addition, the use of ionic liquid (IL)-based electrolyte in the cell has led to a good long-term stability of more than 2000 hours under AM 1.5 G irradiation (100 mW cm -2 ), compared with that less than 100 hours in DSSCs with volatile organic solvent based electrolytes.

Furthermore, this DSSC (a type of IL-based electrolyte ( Note 2 ) ) achieved a high solar-to-electricity conversion efficiency (cell efficiency) of 7.6% under AM 1.5 G irradiation, which is one of the highest performance among DSSCs with IL based electrolytes, and 5.5% efficiency with ionic gel-based electrolyte ( Note 3 ) . It is expected that the cell will be commercialized as an innovative solar generation technology.

Note 1) MK-2 refers to 2-Cyano-3-[5'''-(9-ethyl-9H-carbazol-3-yl)-3',3'',3''',4-tetra-n-hexyl-[2,2',5',2'',5'',2''']-quarter thiophenyl-5-yl] acrylic acid. It is a donor-acceptor type organic dye molecule that consists of carbazol, oligo hexylthiophene and cyano acrylic acid. Its carbazole structure and cyano acrylic acid function as electron donor and acceptor, respectively.

Note 2) Ionic liquid-based electrolyte refers to ionic liquid such as imidazolium iodides and iodine redox ion-based electrolyte.

Note 3) Ionic gel-based electrolyte refers to the quasi-solid electrolyte generated after the addition of gellant (e.g., poly(pyridinium-1,4-diyliminocarbonyl-1,4-phenylene-methylene iodide), etc.) to the ionic liquid-based electrolyte.

Source: AIST /...

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