Reaching 47.1 percent under concentrated lighting, and 39.2 percent under sunlight , researchers in the United States have manufactured a six-junction solar cell that has broken the world record for the highest efficiency in converting solar energy to electricity.
To build the device, the National Renewable Energy Laboratory researchers relied on III-V materials , named for their position on the periodic table, that have a wide range of light-absorbing properties.
Next challenge: more than 50%
Each of the six junctions of the cell (the photoactive layers) is specially designed to capture light from a specific part of the solar spectrum .
The device contains approximately 140 total layers of various III-V materials to support the performance of these bonds, yet it is three times narrower than a human hair. According to Ryan France , study co-author:
One way to reduce the cost is to reduce the required area, and you can do this by using a mirror to capture the light and focus the light to a point. You can then get away with a hundredth or even a thousandth of the material, compared to a flat plate silicon cell. Much less semiconductor material is used when concentrating light. An additional advantage is that the efficiency increases as you concentrate the light.
Currently the main research obstacle to achieving 50% efficiency is reducing the resistive barriers within the cell that impede current flow. Reaching 100% efficiency seems impossible due to the fundamental limits imposed by thermodynamics .