The solar cells at top were made on a roll-to-roll printer from an ink consisting of the rod-shaped inorganic semiconducting nanocrystals shown below. The cells were printed on a flexible metal foil and will be topped with a glass plate. Credit: Solexant
Technology Review reported that solar cells made from nanocrystal-based inks have the potential to be as efficient as the conventional inorganic cells currently used in solar panels, but can be printed less expensively.
Solexant, a company in San Jose currently, is hoping that simpler, cheaper printing processes and materials, as well as lower initial capital costs to build its plants, will give them the leading edge. The company expects to sell modules for $1 per watt, with efficiencies above 10 percent.
To bring down the cost of solar cell manufacturing, companies have been developing thin-film solar cells from semiconductors that don’t match crystalline silicon’s performance but are much less expensive to make.
Solexant’s goal is to make cheap thin-film solar cells with relatively high efficiencies.
Technology Review describes the technology as follows:
The Solexant cells are printed on a metal foil as the substrate. Nanocrystal films are simple to print but have poor electrical properties. Electrons tend to get trapped between the small particles. “The trick with these cells is how to deposit the materials on the fly in a way that makes a very conductive surface,” which in turn ensures decent light-to-electricity conversion, says Alivisatos. Solexant begins with nanocrystals because they’re easier to print, and heats them as they’re printed, causing them to fuse together into larger, high-quality microcrystals that don’t have as many places for electrons to lose their way.
The remaining parts of the solar cell, including the electrical contacts and a light-absorbing layer, are also printed on the flexible metal films. This process allows Solexant to print very large areas. When complete, the cells are cut and then topped with a rigid piece of glass.
Solarexant’s first product, which expects to sell for $1 per watt next year, will contain a single layer of the nanocrystals. The company is currently developing other types of nanocrystals that are more responsive to different bands of the solar spectrum in the hopes of boosting its cells’ efficiency.