A new device pushes sunlight-to-electricity conversion efficiency to 34.5 percent. This marks a world record and an increase of 44 percent on the previous world record holder, Alta Devices in the US, which reached 24 percent.
The device was created by senior research fellow Mark Keevers and director Martin Green of UNSW's Australian Centre for Advanced Photovoltaics. In 2014, they achieved a conversion rate of over 40 percent by using mirrors to concentrate the light. However, the new device uses normal sunlight unconcentrated.
"This encouraging result shows that there are still advances to come in photovoltaics research to make solar cells even more efficient," Keevers said in a statement.
"Extracting more energy from every beam of sunlight is critical to reducing the cost of electricity generated by solar cells as it lowers the investment needed, and delivering payback faster."
The device consists of a 28 square centimetre four-junction mini-module embedded in a prism. When sunlight hits the prism, it is split into four bands by a four-junction receiver. This increases the amount of energy that can be harvested from the sunlight.
On one side of the glass prism is a silicon cell. On another is a triple-junction solar cell. This solar cell has three layers, each of which targets a separate band of sunlight, extracting energy at its most efficient wavelength. The remaining light passes through to the next layer. Light from the infrared band is filtered out and bounced onto the silicon cell, which extracts the energy therein.
Unfortunately in its current form, it's unsuitable for widespread rooftop application; it's simply too complex and would cost too much to manufacture on a large scale. However, the team is working on reducing the complexity.
They also plan to scale the device up. Alta Devices' cell had a much larger area of 800 square centimetres. If the UNSW device can reach that scale, it would leap ahead, even with the marginal loss expected from upsizing.
"What's remarkable is that this level of efficiency had not been expected for many years. A recent study by Germany's Agora Energiewende think tank set an aggressive target of 35 percent efficiency by 2050 for a module that uses unconcentrated sunlight, such as the standard ones on family homes," Green said.
"So things are moving faster in solar cell efficiency than many experts expected, and that's good news for solar energy. But we must maintain the pace of photovoltaic research in Australia to ensure that we not only build on such tremendous results, but continue to bring benefits back to Australia."