Photovoltaics materials research

The Photovoltaics materials research group is focused on developing a deeper understanding of how defects and defect reactions in semiconductor materials (silicon and metal halide perovskites) affect solar cell properties. Prototype solar cells are also developed to directly characterize these effects at the device level. Through customized process steps (e.g., gettering steps, hydrogen passivation), the material quality is continuously improved. Additional key areas include new approaches to surface passivation, charge carrier-selective contacts, and the development of novel measurement methods for photovoltaics.

Stability and industrial relevance

A central focus is long-term stability under field conditions, i.e., exposure to light and elevated temperatures. Our results have already made significant contributions to improving the stability of crystalline silicon solar cells—for example, through the development of methods to prevent certain light-induced defects. We were the first to demonstrate that the dopant has a significant influence on the light-induced degradation of silicon solar cells. The choice of dopants in today’s industrially produced solar cells is largely based on these investigations. We also developed thermal processes that result in significantly reduced degradation. In the field of surface passivation, our group developed standard passivation layer systems such as Al₂O₃/SiNₓ stack layers, which are now implemented in most industrially produced solar cells.

Perovskites: materials and characterization

A current research focus involves the development of low-bandgap metal halide perovskite thin films and the fabrication of solar cell prototypes based on them. We are also currently developing new, easy-to-use characterization methods for perovskite thin films, enabling contactless determination of their electrical properties. Methods for the quantitative determination of surface recombination in passivated perovskites are also being developed, in order to evaluate novel materials for use as charge carrier-selective contact layers.