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Sumitomo Chemical Co Ltd developed an organic thin-film solar cell with a high light transmittance and exhibited it at the 2014 Automotive Engineering Exposition, a trade show that runs from May 21 to 23, 2014, in Yokohama, Japan.

Sumitomo Chemical developed the solar cell to confirm that there are potential demands such as for automotive windows and roofs. The light transmittance and size of the exhibited cell are about 50% and 20 x 20cm, respectively. Its conversion efficiency is about half that of an organic thin-film solar cell that does not transmit light and is in the research and development stage, the company said.

"There is no other organic thin-film solar cell that has such a high light transmittance and conversion efficiency and a practical size of 20 x 20cm," it said.

To improve light transmittance and prevent the reduction of conversion efficiency at the same time, Sumitomo Chemical used a long-wavelength-absorbing material that generates electricity with a light whose wavelength is 900nm or longer, which cannot be seen by human eyes. It is possible to realize a perfectly transparent solar cell by making improvements to the material, the company said.

In February 2012, Sumitomo Chemical announced that the conversion efficiency of an organic thin-film solar cell using its material reached 10.6%. This time, however, the company did not disclose the conversion efficiency of the latest cell but highlighted its transmittance.

"Though manufacturers have announced conversion efficiencies higher than 10%, it has not led to the wide use of organic thin-film solar cells," the company said. "Conversion efficiency does not attract users. And we need to develop features other than high conversion efficiency."