CD Laboratory for Nanocomposite Solar Cells

The aim of the research is to develop flexible solar cells that are cost-effective and can therefore be used over large areas. To this end, the production of hybrid materials made from inorganic crystals and organic polymers - nanocomposites - is being optimised.

The selection of suitable materials and the development of suitable manufacturing processes for nanocomposite layers are at the centre of the work. Both aspects are critical for optimising the photovoltaic properties of nanocomposite solar cells. Their effectiveness is based on the optimum composition of the mixture of inorganic crystals with the organic polymer that characterises this hybrid material. On the one hand, a sufficiently large interface between the two types of material must be ensured, and on the other, their phases must be a certain distance apart. This is the only way to ensure efficient charge separation and effective transport of the electrical charge to the electrodes.

Conductive plastics such as poly(p-phenylene-vinylene) (PPV) or polythiophene serve as organic polymers that are combined with oxidic or sulphidic inorganic semiconductors such as zinc sulphide. The special advantage of these materials is that they can in turn be applied to flexible documents such as the plastic polyethylene terephthalate (PET) to form a flexible unit around 200 nm thick for practical use. Another research focus is on the possibilities of achieving a direction-dependent (anisotropic) distribution and ordered shape of the materials in the photovoltaic layers.

To test the research results, current-voltage curves are created under defined radiation conditions. For this purpose, test solar cells are produced by applying the nanocomposite layer between a transparent (indium tin oxide electrode) and a back-surface electrode, such as aluminium, which enables the maximum current flow and the photovoltage to be measured. In this way, the research results can be tested in practice - an important step towards the introduction of technological processes that will ultimately lead to the industrial production of flexible and cost-effective solar cells and solar modules. The researchers at Graz University of Technology (Institute of Chemical Technology of Materials and Institute of Electron Microscopy and Fine Structure Analysis) are working together with the NanoTecCenter Weiz Forschungsgesellschaft to realise this goal.