Japanese Institute Claims Progress with Dye-sensitized Solar Cell

Nov 20, 2008 21:01 Megumi Yoshizawa, Nikkei Electronics

Japan's National Institute of Advanced Industrial Science and Technology (AIST) achieved 7.6% cell conversion efficiency with a dye-sensitized solar cell that uses an ionic liquid electrolyte.

The conversion efficiency is the world's highest level for solar cells of that kind, according to the institute. Compared with the existing dye-sensitized solar cells that use a ruthenium (Ru) complex, the new solar cell features an improved durability and a lower material cost.

The solar cell was fabricated by using a newly-developed organic dye called "MK-2" for the light absorbing material. In the past, the institute used a coumarin dye in an organic solvent electrolyte and achieved a conversion efficiency of 8%.

However, it involved problems including a short electron lifetime and a low electron mobility from the dye to the titanium oxide electrodes. To solve these problems, AIST synthesized the MK-2 dye with a molecular design technology.

The durability of the cell was improved by using a refractory ionic liquid electrolyte. The institute confirmed that the cell has a sufficient durability under relatively mild conditions in simulated sunlight with UV filtered out. While the Ru complex-based dye-sensitized solar cell developed with the organic solvent electrolyte is durable for only 100 hours or less, the durability of the new solar cell is 2,000 hours or longer.

It also ensures a cell conversion efficiency of 5.5% even when an electrolyte consisting of a refractory ionic liquid and a gelling agent with an organic electrolyte oligomer structure is used to improve the durability.

This research was conducted as part of the Industrial Technology Research Grant Program promoted by Japan's New Energy and Industrial Technology Development Organization (NEDO).

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