Yi Cui, a researcher from Stanford University, about whom we’ve been talking about many times lately, has discovered how nanoscale wires, pores, bumps and other material textures can improve the performance of solar cells dramatically. They could even serve as self-cleaning coatings, because of their highly hydrophobic properties.
“Many methods are really complex and don’t solve the problem,” says Cui. Lithography can be used to carve out nanoscale features with precise dimensions, but it’s expensive and difficult. Simpler techniques, such as spin-coating a surface with nanoparticles or using acids to etch it with tiny holes, don’t allow for much precision.”
Cui and his team used a manufacturing process used to manufacture flexible packaging, consisting of a rod wound with wires which is used to evenly deposit a liquid coating that contains silica nanospheres. The surface treated this way will have several nanoscale structural properties.
Changing the size of the nanoparticles, using wires of different diameters, and applying subsequent chemical treatments can further modify the properties of the surface. The coating method is compatible with roll-to-roll processes used to print flexible devices on plastic, metal, and other materials, and it can also be used on rigid surfaces like glass.
Cui describes how they coated a solar cell with the superhydrophobic surface by depositing metal and amorphous silicon on the surface. The resulted solar cell absorbed 42% more light than a flat one having the same quantity of materials.
“This work demonstrates a simple yet effective method for achieving controlled assembly of nanospheres over large areas,” says Ali Javey, a professor of electrical engineering and computer science at the University of California, Berkeley. “It could present a route toward improved efficiencies in thin-film solar cells, without increasing the cost or the process complexity.”
Cui’s work may not yield the results obtained by others, but it may serve as an approach towards making better solar cell coatings.
