Self-assembling nanoparticles to harvest solar energy

Solar-thermal technology such as concentrated solar power or on a smaller scale solar water heating is a promising option for growing renewables penetration but it is challenged by suppressing the energy dissipation while maintaining a high absorption.

But now researchers from Harbin University, Zhejiang University, Changchun Institute of Optics, and the National University of Singapore believe they can overcome this challenge with an absorber comprised of iron oxide nanoparticles that self-assemble to form an organised quasi-periodic material structure based on their interactions with nearby particles without any external instructions.

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This structure, which is scalable, was found to provide a significant solar absorption >94% and ideal passive suppression of thermal emissivity <0.2.

Tested under natural sunlight, the harvester reached a sustaining open circuit voltage of >20mV/cm2 without a heat sink.

With further work, the researchers believe the technology should pioneer next generation, high performance, economical and practical solar co-harvesting systems.

"We hope our quasiperiodic nanophotonic structure will inspire other work," said author Ying Li of Zhejiang University.

"This highly versatile structure and our fundamental research can be used to explore the upper limit of solar energy harvesting, such as flexible scalable solar thermoelectric generators, which can serve as an assistant solar harvesting component to increase the total efficiency of photovoltaic architectures."

The solution avoids the costs and limited flexibility and scalability of traditional nanophotonic structures fabrications as a result of the rigidity of their patterns.

Its quasi-periodicity, i.e. primarily an alternating and consistent pattern but with random defects that do not affect the performance, also increases its scalability potential.