Researchers from Brown University and the National Renewable Energy Lab (NREL) managed to attain better than a 15% energy conversion efficiency from perovskite solar cells larger than one square centimeter area, by using a newly developed fabrication method.
Efficiency of over 20%, which rivals traditional silicon cells, has already been reported in perovskite cells, but such high efficiency ratings have been achieved using cells only a tenth of a square centimeter in size, too small to be used in a solar panel. This research, however, shows that it is feasible to obtain 15% efficiency on cells larger than a square centimeter through improved processing.
The fabrication process designed by the researchers builds on a previously reported method, previously developed in Brown University. Perovskite precursors are dissolved in a solvent and coated onto a substrate. Then the substrate is bathed in a second solvent (called anti-solvent) that selectively grabs the precursor-solvent and takes it away. The result is an ultra-smooth film of perovskite crystals. The researchers in this study developed a trick to grow the perovskite crystals to a larger size - to add excess organic precursor that initially "glues" the small perovskite crystals and helps them merge into larger ones during a heat-treatment, which then bakes away the excess precursor.
The method yields a film with fewer defects and higher efficiency. The 15% efficiency reached in this latest work is a good start, but there’s still room to improve. Ultimately, the researchers say that they would like to reach 20-25% in large-area cells.
In September 2015, Brown University secured a $4 million grant for perovskite solar cell research.