Researchers everywhere are working on developing better solar cells: ones with higher power output, ones that can adhere to any surface, ones that cool or clean themselves, etc. Upping the efficiency of solar cells is probably the biggest focus. Right now, commercial solar cells can convert about 15 to 25 percent of the energy from sunlight into electricity. The holy grail for years has been reaching a 50 percent conversion efficiency.
In labs, researchers have been able to hit efficiencies as high as 44.7 percent, but the start-up Semprius says they have a technique for stacking solar cells that would lead to that magic 50 percent number, and not just in a lab. Not only that, but because the solar cells are small and cheap to manufacture, the company believes that this technology could also lead to solar power cheaper than natural gas.
MIT Technology Review says, "Semprius has come up with three key innovations: a cheap, fast way to stack cells, a proprietary way to electrically connect cells, and a new kind of glue for holding the cells together. In its designs, Semprius uses tiny individual solar cells, each just a millimeter across. That reduces costs for cooling and also helps improve efficiency."
Stacking solar cells isn't a totally new idea, but Semprius has dramatically improved upon that idea. Using its technique, Semprius has been able to demonstrate three semiconductor materials stacked on top of a fourth solar cell. This device has been able to reach efficiencies up to 44.1 percent. Also, the technique allows Semprius to reuse the expensive crystalline wafers that multijunction solar cells are grown on, driving down production costs.
The company thinks that within three to five years it will be able to build solar cells consisting of two stacked multi-junction devices, which would be a total of five or six semiconductors. That device could actually go beyond 50 percent efficiency.
Even bette, at 80 to 100 megawatts a year of manufacturing capacity, solar cells achieving 50 percent efficiency could reach costs of five cents per kilowatt-hour, which beats the current price of natural gas at 6.4 cents per kilowatt-hour.