Dye-sensitized solar cells, or Grätzel cells, have been invented by Michael Grätzel in 1991. Grätzel is a chemistry professor at the École Polytechnique Fédérale de Lausanne in Switzerland, and since now they didn’t have any commercial purpose, being developed just for research. The first company who is about to commercialize Grätzel’s cells is G24 Innovations, and the first use of the cells will be in a solar-powered backpack.