Spray-on solar cells

“My dream is that one day you’ll have two technicians wearing Ghostbusters-style backpacks come to your house and to spray your roof.” But Illan Kramer, a professor at the University of Toronto in Canada, is not dreaming of artists like the ones who paint life-size frescoes on the walls of EDF power plants and dams. His technicians will spray photosensitive micro-particles onto surfaces – allowing everything from car bonnets to phone cases to store energy from the sun, like the cells in photovoltaic panels do, and convert it into electric current.While the magic spray’s energy conversion rate currently peaks at under eight per cent, the researchers are confident they can drastically improve its efficiency.
Replacing siliconKramer’s team’s invention, named SprayLD, is inspired by research carried out by scientists at Sheffield University. As silicon, the material most commonly used for solar cells, requires a lot of energy to extract and is very expensive to produce, the British researchers used perovskite (calcium titanate) to make photovoltaic nano-cells. Their main benefit is that they absorb light from just a micrometre in size and can therefore be mixed with paint into a spray. This is a major development. “The best certified efficiencies from organic solar cells are around 10 per cent. Perovskite cells now have efficiencies of up to 19 per cent. This isn’t that far behind silicon at 25 per cent,” explains Professor David Lidzey. According to the researchers, this means that industrial-scale production is feasible – the only drawback being that, in a vaporized state, energy efficiency falls to 11 per cent.Atomic scaleTo go one step further, the team from Toronto has explored a new approach. SprayLD vaporizes a liquid containing minuscule, light-sensitive materials called colloidal quantic dots. It is blasted onto flexible surfaces such as film and plastic in the same way ink is applied to a roll of paper to print a newspaper. The major advantage of this “roll-to-roll” coating method is that it allows the material to be deposited in layers the thickness of an atom. This is much quicker and more efficient than the traditional chemical approach. Furthermore, by modifying the size of the nanoparticles, the vaporized cells can absorb different parts of the solar spectrum – improving the energy recovery potential.High-tech tinkeringWhile the magic spray’s energy conversion rate currently peaks at under eight per cent, the researchers are confident they can drastically improve its efficiency. The Toronto team has already estimated that the roof of a car could power three 100-watt light bulbs or 24 compact fluorescent lights.This powerful invention draws on the best of cutting-edge technology, yet makes use of cheap materials: SprayLD’s design is based on mini paint guns available in all art shops, and spray nozzles used to cool steel in steelworks.To go further
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