Nanophotovoltaics and photon management
One of the main scientific, technical and economic challenges of the human society in the 21st century will be to reduce the consumption of fossil energies at the favor of renewable and thus sustainable energy sources. Along the lines of this development the ultimate goal is usually to decrease the price for renewable energies to make it competitive to grid power. If that goal is reached it will be more appealing on a long perspective to rely on renewable energies. This goal can be reached either by enhancing device efficiencies or by reducing their costs.
For solar cells, the efficiency enhancement can be obtained following two approaches. One way may be the exploration of energy harvesting and conversion in novel materials, which must be designed and tested under environmental conditions for this purpose. Another path may be the exploration of optimization approaches typically referred to as photon management. In general, photon management in solar cells aims at optimizing the localization of light in the light absorbing material and reducing typical loss mechanisms such as reflection. This is accomplished by introducing a large variety of micro- and nanostructures into the solar cell in order to enhance the optical path length of photons in the relevant spatial domains.
The research of our group tackles both aspects, i.e. investigating potentials of the improvement of state-of-the-art solar cells and developing new concepts for micro- and nanostructured photonic surfaces. Our studies comprise deterministic as well as randomized structures. Typical examples are non-reflecting nanostructured "black" silicon, dielectric diffractive gratings for enhanced light trapping, or plasmonic nanostructures for the optimization of light concentration. Together with several experimental partners we investigate the whole chain of design, technological realization and parameter optimization, optical and electrical characterization and evaluation of the potential for implementation in real-world solar cells. Emphasis is also put on resonant as well as non-resonant processes for the localization of light and an efficient conversion of light energy into usable energy forms.