Metal-halide perovskite materials in particular show great potential as low cost light harvesting materials for thin-film photovoltaics. One of the leading candidates among metal halide perovskites is formamidinium lead triiodide (FAPbI3), which has emerged as the most promising semiconductor for highly efficient and stable perovskite solar cells.
The EPFL team led by Professor Michael Grätzel with researchers from China and Korea, uses a technqie called anion engineering to boost the crystallinity of the FAPbI3 films and eliminates defects. By introducing the pseudo-halide anion formate (HCOO−) to the mix, they were able to suppress structural defects that usually present at grain boundaries and at the surface of perovskite films.
This takes the efficiency up to the levels of tandem cells at 26 percent, and is a potential material for large perovskite solar cells where the efficiency is currently 18 percent.
“Our findings provide a direct route to eliminate the most abundant and deleterious lattice defects present in metal halide perovskites, providing a facile access to solution-processable films with improved optoelectronic performance,” said Grätzel in a paper in Nature.
This gave a conversion efficiency up to 25.6 percent with operational stability of at least 450 hours, and intense electroluminescence, with external quantum efficiency over 10 percent.
Other contributors include the Ulsan National Institute of Science and Technology (UNIST), Korea Institute of Energy Research (KIER), Chinese Academy of Sciences, EPFL Laboratory for Molecular Engineering of Optoelectronic Nanomaterials and Kyung Hee University.
However researchers are also looking to avoid using lead in such systems and replace the lead halide perovskite materials.
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