Most photovoltaic cells primarily convert visible light, as well as a small portion of near infrared light, into electricity, leaving a significant portion of the 174,000 terawatts of solar energy – the equivalent of 4 million tons of oil – that reaches Earth every second untapped.
That could soon change thanks to research from a team at the Korean Institute of Science and Technology (KAIST).
Broadband and Large-Scale Capture
To absorb additional wavelengths, scientists are proposing the use of plasmonic supraspheres. These structures are made up of thousands of gold nanoparticles capable of interacting collectively with light, self-assembling into spherical superparticles. When dropped onto a flat surface, these superparticles form a dense, textured film that can more effectively capture radiation. This innovation represents a potential leap forward in maximizing solar energy harvesting.
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This innovation allows for the absorption of ultraviolet wavelengths, which represent 50 to 55% of the spectrum, as well as all near and far infrared rays, in addition to visible light.
Up to 90% of the Spectrum
Whereas films made of nanoparticles already exist, plasmonic supraspheres function differently by utilizing multiple types of resonances to more effectively trap photons. This approach enables the absorption of up to 90% of the solar spectrum – a figure previously unattainable – and generates power nearly 2.4 times greater than conventional nanoparticle coatings. This represents a significant advancement in the field.
To achieve this result, the Korean researchers first relied on computer simulations to optimize the design of the supraspheres, adjusting their diameter to maximize absorption of wavelengths.
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They then applied them dropwise onto the ceramic surface of a commercial thermoelectric generator to form a coating, and were able to observe double the absorption compared to a conventional film of gold nanoparticles.
this technology, which also has the advantages of being inexpensive and easy to implement thanks to a solution deposition process, could significantly improve the efficiency of thermal and photothermal solar systems. It could also make hybrid photovoltaic-thermal systems more efficient by better utilizing wavelengths dedicated to heat production.
