Researchers from KAUST have found that graphene quantum dots could expand the usable spectral region of light in silicon solar cells to boost their efficiency and provide a more cost-effective way for energy production.
Graphene quantum dots are small flakes of graphene that are useful because of their interaction with light. One of these interactions is optical downconversion, which is a process that transforms light of high energies into lower energy (for example, from the ultraviolet to the visible). Silicon absorbs light very efficiently in the visible part of the spectrum, and therefore appears black. However, the absorption strength of silicon for ultraviolet light is much smaller, meaning that less of this light is absorbed, reducing the efficiency of solar cells in that part of the spectrum. One way around t this problem is the downconversion of ultraviolet light to energies where silicon is a more efficient absorber.
Graphene quantum dots hold great potential for this purpose. They are relatively easy to manufacture, and while the dots are almost transparent to visible light, which is important to pass that light through to the solar cell, they are efficient in converting UV light to lower energies. The researchers integrated the quantum dots on a silicon solar cell device. The efficiency of the solar cells increased in comparison to control samples.
The researchers add that the test sample solar cells measured so far have not yet been optimized to be closer to the record-breaking performances seen in silicon. The researchers therefore plan to combine some other enhancement technologies previously achieved in similar devices.