Solar energy comprises different wavelengths of light. While 43 percent of solar energy is visible light, 5 percent is UV light. It’s important for materials to absorb visible light in order for solar cells to present better, more efficient energy sources.
This concept generally encompasses light harvesting, or using the sun for energy. In a new discovery, researchers likened to quantum-confined composite materials. There exists a quantum-confined bandgap that, when narrowed, allows UV light to be absorbed.
Researchers for the first time have initiated a quantum-confined bandgap narrowing mechanism where UV absorption of the graphene quantum dots and titanium dioxide nanoparticles can easily be extended into the visible light range.
The increased visible light absorbance happened when the researchers mixed titanium dioxide particles with graphene quantum dots. Graphene is obtained from a number of precursors. On a basic level, you can think of graphene quantum dots as a single layer of graphene, observed in nanometers.
Dr. Qin Li explained the application of solar cells in this way, “Wherever there is abundant sun we can brush on this nanomaterial to harvest solar energy to create clean water,” she says. “This mechanism can be extremely significant for light harvesting. What’s more important is we’ve come up with an easy way to achieve that, to make a UV absorbing material to become a visible light absorber by narrowing the bandgap.”
In the past, researchers have attempted to modify titania’s abilities to absorb visible light by metal ion doping, carbon doping, nitrogen doping, and hydrogenation. All of these methods include changing the pressure or temperature to levels necessary in achieving those modifications.
It remains to be seen whether graphene quantum dots can be mixed with other semiconductors as well. Further experimentation could aim to manipulate different combinations as well as graphene quantum dot sizes.