Preliminary research has shown that a properly designed hyperbolic metamaterial can act as an edge filter for a photovoltaic cell that reflects infrared radiation. And this leads to the heating of the cell and, consequently, to a decrease in its energy efficiency.

– In our project, we perform both a full simulation of electrical and optical parameters, and we verify this assumption experimentally – says Bartosz Fetliński, D.Sc. Eng., from the Faculty of Electronics and Information Technology, head of the research team. – We create the structure of a hyperbolic metamaterial composed of ultra-thin layers, with a thickness of the order of nanometers. The structure created in this way will allow, among others, to obtain filters with a very sharp edge, very well filtering and having the capability of obtaining a rapid transition from transmission to absorption or reflection.

It was these features of hyperbolic metamaterials that prompted the researchers to use them in photovoltaic panels.

– The photons’ energies of infrared radiation are smaller than the photons of visible light and are not used to produce electricity at all, but are absorbed by various elements of the photovoltaic module – explains Bartosz Fetliński, D.Sc. Eng. – There is no energy gain from this, but it heats the module instead. If a photovoltaic module is equipped with such a filter of metamaterial, the permeability of photons from this useful range is good, and the rest that they heat, we can get rid of.

Time of Trials

Experimental verification of the modelled metamaterial structures is carried out in cooperation with the Institute of Microelectronics and Photonics of the Łukasiewicz Research Network (IMiF) and the Institute of Physics of the Polish Academy of Sciences (IFPAN). At the Faculty of Electronics and Information Technology of the Warsaw University of Technology, the work of the research team will be supported by Prof. Robert Mroczyński, who by means of magnetron atomization is able to create a part from the layers.

– Until now, hyperbolic materials have not been used in this way, so our project is characterized by high scientific innovation – says Dr. Fetliński. – Therefore, there are no reliable characteristics of these materials in the literature that could be used in our project. It happens that the properties are described in the case of using one method of applying layers, while there is no further description when using another.

Currently, the purchase of substrates, which are of key importance for the project, is being finalised. Their quality affects the homogeneity of the produced hyperbolic metamaterials, which consist of thin layers, sensitive to the properties of the substrate.

– The solution proposed by us is characterized by conceptual and implementation simplicity and can be used in any commercially available PV modules, which is its significant competitive advantage over the solutions proposed so far, requiring significant interference in the structure of the cell or module – says Dr. Fetliński.

The research team consists of: Bartosz Fetliński, D.Sc.Eng., Bartosz Fetliński, D.Sc.Eng., Marcin Kieliszczyk, MSc. Eng.; Robert Mroczyński, D.Sc.Eng., Professor of WUT.

The project "Use of hyperbolic metamaterial for the purpose of increasing the energy yield of photovoltaic modules" is financed under the "Excellence Initiative – Research University" program implemented at the Warsaw University of Technology. The idea received support in the competition of the POB Research Center for Photonics Technologies.