Solar cell inventor Professor Michael Grätzel of the Lausanne Federal Technology Institute has been awarded the 2010 Millennium Prize, a Finnish award established to steer the course of technological development to a “more humane direction” and handed out once every two years.
Grätzel’s invention, the nanostructured dye-sensitized solar cell, also known simply as the dye solar cell (DSC) or Grätzel cell, mimics the energy processes of green plants or photosynthesis.
The prize of nearly $1 million (£683 million) was awarded by the Technology Academy Finland, an independent fund established by Finnish industry and the Finnish state in partnership. The organisation said based on the materials and manufacturing steps involved, the cost of Grätzel cells could come under the $1 (68 pence) per watt, perceived as the cost breakthrough point for solar electricity on a global market level.
DSC is a third generation photovoltaic technology. The technology is made of low-cost materials and the committee noted it does not need an elaborate apparatus to manufacture. In 1988 Grätzel’s team tested the first dye-sensitised mesoscopic titanium oxide material on solar cells, and in 1991 Grätzel’s Nature paper on dye-sensitised solar cells was published. Mass production of DSC cells began in 2009.
In traditional photovoltaic cells silicon acts as both the source of electrons, as well as conductor of the charge carriers. DSC cells separate light harvesting from charge carrier transport, mimicking the principles of solar energy conversion. Only 10 micrometers thick, the mixture is sandwiched between two glass plates or embedded in plastic. Light striking the dye frees electrons and creates “holes” – the sites of positive charge that result when electrons are lost. The semiconducting titanium dioxide particles collect the electrons and transfer them to an external circuit, producing an electric current.
“It was a wonderful experience to win the grand prix, and of course a tremendous honour,” Grätzel told the BBC. He explained the cells use nanocrystal films in which the particles are so small that they don’t scatter light. “You can imagine using those cells as electricity producing windows. What’s very exciting is that you collect light from all sides, so can capture electricity from the inside as well as the outside. You could think that the glass of all high-rises in New York would be electricity generating panels,” he said.