Nanostructured films to make solar energy conversion more efficient and cheaper

Washington, Jan 10 : Researchers have developed a new method of makinganostructured thin films, which might make solar energy conversion more efficient and cost effective in the future.

According to researchers, the new method takes advantage of two nanotech methods which are used for engineering solar cell materials.

These two methods can experiment with and control how a material generates, captures, transports, and stores free electrons--properties that are important for the conversion of sunlight into electricity.

While one method uses thin films of metal oxide nanoparticles, such as titanium dioxide, doped with other elements such as nitrogen, the second employs quantum dots--nanosize crystals--that strongly absorb visible light.

What these tiny semiconductors do is to inject electrons into a metal oxide film, or "sensitize" it, to increase solar energy conversion. "Combining these two approaches appears to yield better solar cell materials than either one alone does," said Jin Zhang, professor of chemistry at the University of California, Santa Cruz .

For the research, Zhang and a team of researchers from California, Mexico, and China , created a thin film doped with nitrogen and sensitized with quantum dots.

When tested, the new nanocomposite material performed better than predicted--as if the functioning of the whole material was greater than the sum of its two individual components.

This resulting hybrid material offered a combination of advantages.

Nitrogen doping allowed the material to absorb a broad range of light energy, including energy from the visible region of the electromagnetic spectrum. The quantum dots also enhanced visible light absorption and boosted the photocurrent and power conversion of the material.

Also, when compared with materials that were just doped with nitrogen or just embedded with cadmium selenide quantum dots, the nanocomposite showed higher performance, as measured by the "incident photon to current conversion efficiency" (IPCE).

"The nanocomposite's IPCE was as much as three times greater than the sum of the IPCEs for the two other materials," said Zhang.

The hybrid material could also potentially be useful in devices for converting carbon dioxide into hydrocarbon fuels, such as methane.

In fact, not only can the nanocomposite material used to enhance solar cells, but also to serve as part of other energy technologies.

"We have discovered a new strategy that could be very useful for enhancing the photo response and conversion efficiency of solar cells based on nanomaterials," said Zhang.

ANI