New Solar Cells Could Reduce Cost and Improve Efficiency

10/30/2017 |

Silicon-based multijunction solar cells can reach almost 36% efficiency


Multijunction solar cells have the potential to provide an efficient and lower cost solar option than cells made only from rare earth and transition metals.

In a collaborative effort, researchers at the U.S. 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) have proven higher potential of silicon-based multijunction solar cells in a recent paper appearing in Nature Energy.

The researchers developed tandem solar cells with record efficiencies of sunlight conversion into electricity under one-sun illumination. Cells made only from rare earth and transition metals (Groups III and V in the Periodic Table) show high efficiencies, but they are often much more expensive. Using silicon-based materials in these cells is a major step.

“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,” says Adele Tamboli, one of the NREL authors of the paper. “It opens the door to develop entirely new multijunction solar cell materials and architectures.”

The research team found that the highest dual-junction efficiency (32.8%) came from a tandem cell stacking a layer of gallium arsenide that NREL developed on top of a film of crystalline silicon by CSEM. In two other multijunction solar cells, the researchers achieved efficiencies of 32.5% and 35.9%.

The PV market is dominated by single-junction silicon solar cells, but their efficiencies range from 17-24%. Transitioning from silicon single-junction cells to silicon-based dual-junction solar cells will allow manufacturers to improve efficiency beyond 30% while still making use of expertise in making silicon solar cells. The main hurdle for their production is cost, as it will take manufacturers to fully embrace this technology for prices to drop.

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