Invisibility layer increases solar panel efficiency

October 4, 2015

By eeNews Europe

The researchers counted how much area of the solar panels that is covered by the so-called contact fingers. Wherever the contacts are located, they prevent that the light reaches the active solar panel area, reducing the panel’s overall efficiency. Since this are adds up to 10%, the energy loss is significant.

"Our experiments proved that the invisibility layer almost eliminates the shadowing effect of the contact fingers", says Martin Schuman from the Institute for Applied Physics at KIT. The doctoral candidate has performed the experiments and simulations with the invisibility layer. Together with researchers from the universities of Aachen, Freiburg and Halle, KIT physicists headed by project manager Carsten Rockstuhl have developed and refined the concept of an optical invisibility cloak with the goal of conducting the light around the contact finger.

Normally, the aim of the invisibility cloak research is making a certain object disappear to the observer. Towards this end, the light is conducted around the object. In this case however, the focus was not making the contact finger "disappear" but to divert as much light as possible and thus to make the panel area under the contact finger productive.

The scientists investigated two options. In either case, a polymer layer is applied to the solar panel. This layer needs to have exactly defined properties – either a refractive index that varies by location or a specific surface geometry. The second concept appears to be particularly promising since it can be applied to the cost-effective mass production of solar panels. The surface has grooves on it that are aligned with the contact fingers, causing the incident light to be refracted away from the contact fingers and finally striking the active surface of the solar panel.

In a model experiment, the researchers proved that both approaches are basically suited to achieve the desired effect. As the next step they plan to apply the invisibility layer to a solar panel to determine the actual efficiency gain. The physicists are optimistic: "Such a layer should reduce the shading effects caused by the contacts and heighten die efficiency by up to ten percent", says Schumann.

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