The overwhelming majority of photovoltaic (PV) solar panels available on the market today use silicon-based solar cells that are between 17 percent and 24 percent efficient at converting sunlight into electricity. But new research shows that multijunction silicon solar cells have reached 35.9 percent efficiency levels in testing, coming close to efficiency levels of much more expensive multijunction solar cells.
What does that mean to the average homeowner or solar developer? More power produced over a smaller area, as less solar panels would be needed if they reach higher efficiency levels.
The new research is the result of a collaboration between the Department of Energy’s National Renewable Energy Laboratory (NREL), the Swiss Center for Electronics and Microtechnology (CSEM), and the École Polytechnique Fédérale de Lausanne (EPFL). The researchers published their work, “Raising the One-Sun Conversion Efficiency of III–V/Si Solar Cells to 32.8% for Two Junctions and 35.9% for Three Junctions,” in the newest issue of Nature Energy. The lead author of the study is Stephanie Essig, a former NREL post-doctoral researcher who now works at EPFL in Switzerland.
“This achievement is significant because it shows, for the first time, that silicon-based tandem cells can provide efficiencies competing with more expensive multijunction cells consisting entirely of III-V materials,” said NREL scientist Adele Tamboli. “It opens the door to develop entirely new multijunction solar cell materials and architectures.”
Currently the most efficient solar cells have reached 46.0 percent efficiency levels. Those cells, developed by Soitec and the Fraunhofer institute are using expensive materials and aren’t likely to end up in conventional solar panels any time soon. However, these new silicon-based multijunction solar cells could be incorporated into conventional silicon panels and manufacturing techniques while still boosting their efficiency significantly.
The new research covered dual-junction and triple-junction cells. It found that gallium arsenide, dual-junction cells reached up to 32.8 percent efficiency level and triple-junction silicon cells with gallium indium phosphide and gallium arsenide reached an efficiency level of 35.9 percent. The research didn't cover another promising technology, perovskite crystals, which research has shown could reach 31 percent efficiency.
At this point the cells would cost gallium indium phosphide cells would cost $4.85 per watt to produce and gallium arsenide-based cells would cost $7.15 per watt to produce. That’s far higher than the cost of silicon PV cells that now cost less than 1 a watt to produce. However, NREL said that as manufacturing of dual or triple-layer silicon-based cells increases they predicted the cost per watt could fall to 66 cents for a gallium indium phosphide-based cell and to 85 cents for the gallium arsenide-based PV cells.Tweet