Cloaking Principle Could Boost Solar Cell Performance

Facebook X LinkedIn Email
Invisibility cloaking may be a long way from reality, but the principle could help improve the performance of solar cells in the near term.

In a series of simulations, researchers at the Karlsruhe Institute of Technology have demonstrated how cloaks made of metamaterials or freeform surfaces could eliminate shadows cast by energy-harvesting components onto the active surfaces of solar cells.

An invisibility cloak (right) guides sunlight past the contacts for current removal to the active surface area of a solar cell.
An invisibility cloak (right) guides sunlight past the contacts for current removal to the active surface area of a solar cell. Courtesy of Martin Schumann/Karlsruhe Institute of Technology.

Contact fingers, which extract electric current, cover up to one-tenth of the surface area of a solar cell. By guiding light around these features, more of the sun's energy could be captured by the solar cell.

"Our model experiments have shown that the cloak layer makes the contact fingers nearly completely invisible," said doctoral student Martin Schumann.

The scientists pursued two approaches, both based on polymer coatings, to achieve the cloaking effect. One approach uses graded-index metamaterials designed using 2D Schwarz-Christoffel conformal maps, and the second uses freeform surfaces designed using 1D coordinate transformations.

In the freeform surface approach, the cloak layer is grooved along the contact fingers. In this way, incident light is refracted away from the contact fingers and toward the active surface of the solar cell.

Freeform surfaces are particularly promising because they could be integrated into mass production processes and can cancel shadows at virtually any angle, the researchers said.

The next step will be to apply cloaking layers to real solar cells. Efficiency is expected to increase by up to 10 percent, Schumann said.

The researchers have already created proof-of-principle demonstrators using direct laser writing of polymer structures on silicon wafers with opaque contacts.

The research was published in Optica (doi: 10.1364/optica.2.000850).

Published: October 2015
freeform optics
Freeform optics refers to the design and fabrication of optical surfaces that do not follow traditional symmetric shapes, such as spheres or aspheres. Unlike standard optical components with symmetric and rotationally invariant surfaces, freeform optics feature non-rotationally symmetric and often complex surfaces. These surfaces can be tailored to meet specific optical requirements, offering greater flexibility in designing optical systems and achieving improved performance. Key points about...
Metamaterials are artificial materials engineered to have properties not found in naturally occurring substances. These materials are designed to manipulate electromagnetic waves in ways that are not possible with conventional materials. Metamaterials typically consist of structures or elements that are smaller than the wavelength of the waves they interact with. Key characteristics of metamaterials include: Negative refraction index: One of the most notable features of certain...
freeform opticsResearch & TechnologyWafersEuropeGermanyKITKarlsruhe Institute of TechnologyMartin SchumannenergysolarphotovolaticcloakingOpticsmetamaterialTech Pulse

We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.