The researchers used high-tech materials called nanophotonic crystals, which are designed to emit precisely determined wavelengths of light when heated.
MIT professors Evelyn Wang said: "As we have demonstrated, for the first time, an STPV device that has a higher solar-to-electrical conversion efficiency compared to that of the underlying PV cell."
During the testing, the nanophotonic crystals are integrated into a system with vertically aligned carbon nanotubes.
Upon heating at a high temperature of 1,000 degrees Celsius, the nanophotonic crystals continue to emit a narrow band of wavelengths of light that precisely matches the band that an adjacent photovoltaic cell can capture and convert to an electric current.
MIT doctoral student David Bierman said: "The carbon nanotubes are virtually a perfect absorber over the entire color spectrum."
Bierman noted that all of the energy of the photons gets converted to heat, which will be re-emitted as light.
Purdue University assistant professor of electrical and computer engineering Peter Bermel said: "To the best of my knowledge, this is a new record for solar TPV, using a solar simulator, selective absorber, selective filter, and photovoltaic receiver, that reasonably represents actual performance that might be achievable outdoors.
"It also shows that solar TPV can exceed PV output with a direct comparison of the same cells, for a sufficiently high input power density, lending this approach to applications using concentrated sunlight."
Researchers are now planning to find ways to make larger versions of the small, laboratory-scale experimental unit and also determine ways to manufacture such systems economically.
The research work is backed by the US Department of Energy-funded the Solid-State Solar Thermal Energy Conversion (S3TEC) Center.
Image: Solar thermal photovoltaics could more than double the theoretical limit of efficiency. Photo: courtesy of the researchers/Massachusetts Institute of Technology.
