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Optical Simulations of Thin-Film Solar Cells

Principal Investigator: Christoph Pflaum, Department of Computer Science, University of Erlangen-Nürnberg (Germany)
HPC Platform: SuperMUC of LRZ

Photovoltaics (PV) plays a crucial role in the current transition from fossil or nuclear energy sources to more environmentally friendly renewable energies. The most commonly used PV devices are based on polycrystalline silicon wafers. Production costs of such devices are relatively high, especially due to their big active layer thicknesses up to 300μm. To reduce production costs thin-film solar cells with active layer thicknesses of only ∼1μm have been developed, often employing amorphous silicon, GaAs (gallium arsenide), CdTe (cadmium telluride) and other expensive and rare materials. Another promising thin-film technology are organic photovoltaics (OPVs). Since all the constituting layers can be processed from solution-processable materials, OPV offers the possibility of cost reduction by large-area roll-to-roll production, using established printing techniques.

In order to improve the efficiency of those solar cells it is necessary to optimize their light trapping ability. There are different techniques to achieve better light harvesting. To evaluate the performance of different setups simulations play a crucial role in identifying structures and materials that will yield more efficient devices.

Optical Simulations of Thin-Film Solar Cells

Illustration 1: Electric field enhancement around a silver nanoparticle incorporated into a solar cells active layer resulting from localized surface plasmons.
© University of Erlangen-Nürnberg; Department of Computer Science

The simulation code developed during the project time at LRZ's SuperMUC cluster allows to get a detailed look into different solar cell setups and the resulting electro-magnetic field distribution inside. This is necessary to evaluate the absorption, transmission and reflection properties of different layers, structures and nano particles incorporated into novel solar cell setups. The biggest challenge is the high resolution, down to the scale of 1nm, that is necessary to correctly resolve the fine structures of rough surfaces between different layers, fine nano wire networks as a replacement for conventional electrodes and small metallic nano particles to benefit from plasmonic effects. Furthermore a wide range of the solar spectrum has to be simulated in order to accurately predict the properties of the solar cells under study.

Optical Simulations of Thin-Film Solar Cells

Illustration 2: Thin film flexible solar cell with SiO2 nano particles and optimized interface structure for better light trapping inside the cell.
© University of Erlangen-Nürnberg; Department of Computer Science

The results obtained by the simulations on HPC system SuperMUC of LRZ are used by the researchers’s project partners to improve their solar cell designs for production.

Scientific contact:
Prof. Dr. Christoph Pflaum
University of Erlangen-Nürnberg
Department of Computer Science
Cauerstraße 11, D-91058 Erlangen (Germany)

April 2015