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.
G24’s backpack will contain dye-coated semicondutor nanocrystals sandwiched between glass panels or embedded in plastic along with an electrolyte. The dye is used to absorb photons and create electrons. Those electrons are transferred to the semiconductor that makes a voltage, usable by an electric circuit.
Grätzel cells are not very efficient at transforming light into electricity, but they have one tough point: they are very efficient in low light, even when the sun is not shining on them, fact that makes them 
superior to thin-film solar cells. Still, this is only one of the advantages of Grätzel cells over thin film. The others are: extended lifetime in full sunlight, wide angle light efficiency, the absorption of diffuse and fluorescent lighting.
G24 Innovations’ backpack solar cell uses a low cost process to produce those cells, and the power is not negligible at all: the panel they are going to install in the backpack will produce up to 500 mW in direct sunlight. G24 uses ruthenium dyes coated on titanium dioxide nanocrystals and an iodide-containing nonvolatile electrolyte. The company’s cells are over 12 percent efficient at converting light into electricity.
Other uses for Grätzel solar cells could be: generating power for advertising billboards, modules that could power your clothes, awnings, tents, and so on. Grätzel is very proud of this moment: “It’s definitely a great moment for us,” Grätzel says. “There has been talk of when the first commercial product will be coming out, and this has happened now.” He added that he expects to see more products on the market soon.
