Energy transition: Sustainable photovoltaics

FAU team accelerating predictions for environmentally friendly and affordable materials for solar cells

Perovskite cells may soon offer an alternative to silicon solar cells. These semiconductors are cheaper to manufacture and feature a high degree of efficiency and a high defect tolerance. This means that defects in the crystal lattice structure barely reduce their performance. One disadvantage, however, is that perovskite solar cells contain lead. In their current study, researchers from the Profile Center Solar at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have developed criteria for defect tolerance in order to accelerate the search for environmentally friendly semiconductor compounds.

Lead-halide-perovskite cells follow a similar principle to traditional solar cells. They have developed at a breakneck speed in the last 15 years. Individual cells can reach degrees of efficiency of over 26 percent. Their manufacturing process is considerably simpler than silicon cells: they have a polycrystalline structure and can be processed at room temperature from the liquid phase, being printed or sprayed in thin layers onto substrates. In contrast, traditional solar cells are based on silicon conductors, each of which are grown from a single, virtually perfect crystal over several stages at extremely high temperatures using huge amounts of energy before being sliced into wafers.

Defect-tolerant material: a lucky discovery

“The discovery of lead-halogen-perovskite was very fortunate,” explains Prof. Dr. Wolfgang Heiß, professor of Materials Science and Engineering at Energie Campus Nürnberg. “The material is intrinsically defect tolerant. Ideally, we would like to replace the lead. Being able to predict which material compounds may be defect tolerant would be a huge step in the right direction.” Together with two other colleagues, Heiß is involved in an interdisciplinary research project combining material sciences, defect characterization and computer-assisted modeling in theoretical chemistry. Their common goal is to facilitate reliable predictions of environmentally friendly materials.By defect tolerance, the FAU researchers mean the ability of semiconductor structures to keep their optoelectronic properties in spite of crystallization defects. They also aim to minimize the influence of existing defects on the lifespan of charge carriers.

Reliable predictions

Theoretical predictions are available at the current time. However, they require considerable computing power, are only available for a select number of semiconductors and often do not correspond to experimental conditions. “Our interdisciplinary research approach combines theory and experiments from the outset, with both methods going hand in hand. This allows us to take a holistic approach to interpreting the results, at the same time as opening the door to new opportunities for finding promising new semiconductor compounds for thin-films solar cells,” explains Dr. Bern Meyer, professor of computational chemistry, who is also involved in the project. The researchers compare experimental methods characterizing the capture of charge carriers in defects with calculations from theoretical chemistry.In the meantime, researchers have pinpointed promising materials as potentially defect tolerant semiconductors. However, the promising candidates still have to be investigated further and verified using experiments. If their properties are confirmed, they could provide the basis for lead-free and therefore more environmentally friendly solar cells.According to Maria Hammer from Energie Campus Nürnberg, this would entail several decisive advantages: “Consumers would be able to benefit from more affordable and long-life solar cells, which would drive the energy transition forward and support sustainable alternatives for producing electricity. As the new materials are printable, lightweight and pliable, it is easier to tailor them to suit various applications and requirements.”

Website Energiecampus Nürnberg Website FAU Profile Center Solar

Further information:

Dr. Maria Hammer
Energie Campus Nürnberg (EnCN)
maria.hammer@fau.de