A new technology developed at the Technion–Israel Institute of Technology may improve the efficiency of photovoltaic cells by nearly 70%.
Current solar cells optimally utilize only a narrow range of the solar spectrum, and the unused radiation outside of that spectrum heats up the device. Thus far, this energy loss has limited the maximum efficiency of solar cells to around 30%.
Technion team is now employing an intermediate process that mediates between the sunlight and the photovoltaic cell, converting the radiation to an “ideal” spectrum. “Harvesting the heat loss in photovoltaics allows for a maximal theoretical efficiency of 70%,” says Professor Carmel Rotschild, who led the study.
To induce this potentially revolutionary improvement in solar efficiency, the researchers have created a new photoluminescence material. “This material is based on known laser materials,” Rotschild says. “The requirements are broad solar absorption and high quantum efficiency at high temperatures and a band gap that matches the photovoltaic cell.”
What is innovative about Technion’s process
“Until now, the only way to harvest heat was through thermal photovoltaics, which requires high temperatures (above 2000 degrees Celsius) and is impractical, with the best demonstration being below 5%,” Rotschild says.
Solving the heat problem
The inspiration for this method comes from optical refrigeration, where the absorbed light is re-emitted at higher energy, thereby cooling the emitter. “Harvest the heat while operating at much lower temperatures (500 C). The energy is stored at the chemical potential and not as heat,” Rotschild says, adding that photoluminescence is a non-thermal radiation.
Rotschild agrees the impact of the breakthrough method on the design of the next generation of solar cells could be significant. “We truly believe this concept has good chance to become a disruptive technology in photovoltaics,” he says.
According to the expert, key applications for this new kind of photovoltaic technology will be concentrated, single junction photovoltaic systems above 45% efficiency. Moving forward with this research endeavor, Rotschild and his colleagues will continue to optimize the material and work on optical management.
Written by Sandra Henderson, Research Editor, Solar Novus Today