A technique inspired by plant photosynthesis

A group of researchers claims to have improved the solar cell system by introducing a new dye in dye-sensitised solar cells.

Ecole Polytechnique Federale de Lausanne (EPFL) has shared that for the first time dye-sensitized solar cell technology incorporates two different dyes –  Phthalocyanines (dyes that are traditionally used in Grätzel cells. Stimulated by light, molecules in the dye transmit an electric charge to titanium dioxide in the cell. But these dyes are only sensitive to a small (red) portion of the light spectrum) and perylenes (these dye molecules are sensitive to the blue and green portions of the visible light spectrum, which the phthalocyanines do not recognise. They transmit their energy to the phtalocyanines, which in turn transmit it to the titanium dioxide in the cell.)

With the incorporation of perylene, the solar cells are now sensitive to a larger range of the visible light spectrum – the red, green and blue wavelengths. The cells produce more energy from the same amount of light.

According to EPFL, the technique has been inspired by the process of plant photosynthesis.

“It’s what we call energy transfer by dipolar interaction,” said EPFL Professor Michael Grätzel, inventor of the dye-sensitized solar cell technology and a lead member of the research team, which includes scientists from EPFL, Stanford University, University of California Berkeley and the Georgia Institute of Technology.  “Until now, the dyes in our cells had the unique role of directly generating the electric charge.”

The model was tested in the EPFL laboratory by Grätzel and Stanford University researcher Brian Hardin.

Results are more than encouraging, according to EPFL. The charge transfer improved by 26% over cells with phthaolcyanine alone.

Led by Stanford, the project, known as CAMP, aims to improve the efficiency and longevity of molecular solar cells, and to develop low-cost solar cell production techniques. Financed by the King Abdullah University of Science and Technology in Saudi Arabia, CAMP has funding of 27 million CHF over five years, nearly 2.2 million CHF of which will be available to Grätzel’s lab in Lausanne.