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Cheap, Efficient Metal-Based Solar Cells May Soon Be Available

Scientists from Rice University, via a path-breaking research discovered a new way, which solar-panel designers could utilize to include light-seizing nanomaterials into future designs.

Bob Zheng who is a graduate of Rice’s Laboratory for Nanophotonics (LANP) and Alejandro Manjayacas who is a postdoctoral research associate, fostered a procedure that solar-engineers could utilize to establish the electricity-manufacturing capability for any arrangement of metallic nanoparticles. The duo applied an inventive theoretical evaluation to findings from a novel and first-of-its-type experimental setup.


Photo Credit: Senior Airman Larry E. Reid Jr

Zheng said that one of the fascinating things that happen when light is shined on a metallic nanoparticle or nanostructure is that a few subset of electrons can be excited “in the metal to a much higher energy level.” He added, “Scientists call these ‘hot carriers’ or ‘hot electrons’”.

Halas also associated with Rice University explained that “hot electrons” are specifically fascinating for solar-energy applications as they can be utilized to make devices, which yield direct current or to urge chemical reactions on otherwise still metal surfaces.

The report said that the most efficient photovoltaic cells of the present days, utilize a combination of semiconductors, which are made from rare and costly elements such as gallium and indium. Halas informed that one method to decrease manufacturing costs would be to inculcate high-efficiency light-assembling plasmonic nanostructures with low-cost semiconductors like metal oxides. Apart from being less costly, the plasmonic nanostructures have optical assets, which can be accurately regulated by adjusting their shape.

Halas said that they can alter plasmonic structures to hold light across the whole solar spectrum. “The efficiency of semiconductor-based solar cells can never be extended in this way because of the inherent optical properties of the semiconductors,” he added.

Zheng explained that plasmonic-centered photovoltaics have usually had little efficacies, “and it hasn’t been entirely clear whether those arose from fundamental physical limitations or from less-than-optimal designs.”

Manjayacas said that to make photon’s energy useful, it should be soaked up rather than dispersed back out. Due to this reason, majority of the earlier theoretical studies had concentrated on knowing “the total absorption of the plasmonic system.”

He informed that a recent instance of such a study arrives from a groun-breaking experiment by Ali Sobhani, another Rice graduate, where the absorption was focused near a metal semiconductor boundary.

Manjayacas stated that from this point of view, one can establish the total number of electrons manufactured, but it offers no method of establishing “how many of those electrons are actually useful, high-energy, hot electrons.”

He said that compared to Sobhani, Zheng’s figures permitted a better evaluation as the latter’s experimental setup carefully strained high-energy hot electrons from their less-energetic equivalents. To achieve this, Zheng made two kinds of plasmonic devices – each device comprised of a plasmonic gold nanowire on a semiconducting layer of titanium dioxide.

In the first setup, the gold was situated right on the semiconductor, and in the second, a fine layer of titanium was rested between the gold and the titanium dioxide. The first setup made a microelectronic structure known as “Schottky barrier” and permitted hot electrons only to move from the gold to the semiconductor. On the other hand, the second setup permitted every electron to move.

Manjayacas said that the experiment distinctly indicated that a few electrons are hotter than the rest, and it permitted them to link those with certain assets of the system. He added that specifically they discovered that hot electrons were not linked with total absorption. “They were driven by a different, plasmonic mechanism known as field-intensity enhancement,” he stated.

Zheng and Manjayacas informed that they are performing more tests to adjust their system to improve the output of the hot electrons.

Halas said that this study is a significant move toward the comprehension of plasmonic technologies for solar photovoltaics, and also it offers a key to elevating the efficacy of plasmonic hot-carrier devices and indicates that they can be beneficial for switching sunlight into usable electricity.

The study has been published in the July 13 issue of the journal “Nature Communications”.

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