Fraunhofer builds 68.9% efficiency solar cell for laser energy transfer

Germanys Fraunhofer ISE (Institute for Solar Energy Systems) has reportedly achieved a 68.9% rate of conversion efficiency for an III-V solar cell that can be utilized in laser energy transmission systems.

Researchers from the Institute were quoted saying that the new form of energy transfer, termed power by light, delivers laser energy either through the air or by an optical fiber to a photovoltaic cell with properties matching the wavelength and power of the monochromatic laser light.

The scientists also explained that compared to power transmission through conventional copper wires, power by light systems provide high efficiency for applications requiring a galvanically isolated power supply, or completely wireless power transmission, and suchlike.

Laser energy transmission systems can be compared to energy transmission systems based on microwave technology.

They transform the power source into an emitter that creates directional electromagnetic radiation, which is subsequently absorbed in a receiver.

According to experts, these systems can be used for monitoring passive optical networks, high-voltage lines, fuel sensors in aircraft tanks, and wind turbines among other things.

It is worth noting that the cell was first built with layers mounted on gallium arsenide substrate, which was subsequently cleared away, and a highly reflective mirror was affixed to the posterior surface of the ultra-thin semiconductor structure.

Furthermore, optical optimization of the reflector was done through a combination of silver and ceramic, while the cell's absorber drew on p-type aluminum gallium arsenide and nitrogen-doped gallium arsenide.

The Head of the research team at Fraunhofer ISE, Henning Helmers, was quoted saying that the thin film approach brings in two distinct advantages for efficiency.

First off, the cell traps the photons, maximizing the absorption for photon energies near the bandgap and simultaneously reducing transmission and thermalization losses, Helmers stated.

Furthermore, the additional internally generated photons through radiative recombination are trapped and recycled. This, he explained, extends the effective carrier lifetime, thus increasing the voltage.

The German research institute has stated that the gallium arsenide cell has the highest efficiency rate for conversion of light into electricity, to date.

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