The thin silicon membrane uses a disordered honeycomb layer to maximize the absorption of sunlight. (Image: University of Surrey)

In a paper published in American Chemical Society’s ACS Photonics, a University of Surrey team detailed how they used characteristics of sunlight to design a disordered honeycomb layer to lie on top of a wafer of silicon. Their approach is echoed in nature in the design of butterfly wings and bird eyes. The honeycomb design enables light absorption from any angle and traps light inside the solar cell, enabling more energy to be generated.

In the laboratory, they achieved absorption rates of 26.3 mA/cm2, a 25 percent increase on the previous record of 19.72 mA/cm2 achieved in 2017. They secured an efficiency of 21 percent but anticipate that further improvements will push the figure higher, resulting in efficiencies that are significantly better than many commercially available photovoltaics.

Dr Marian Florescu  from the University of Surrey’s Advanced Technology Institute (ATI) said, “One of the challenges of working with silicon is that nearly a third of the light bounces straight off it without being absorbed and the energy harnessed. A textured layer across the silicon helps tackle this and our disordered, yet hyperuniform, honeycomb design is particularly successful.”

Dr Florescu continued, “There’s enormous potential for using ultra-thin photovoltaics. For example, given how light they are, they will be particularly useful in space and could make new extra-terrestrial projects viable. Since they use so much less silicon, we are hoping there will be cost savings here on Earth as well, plus there could be potential to bring more benefits from the Internet of Things and to create zero-energy buildings powered locally.”