New Method to Harvest Solar Energy from Light

There may be a new way to harvest energy from light. Scientists have discovered a method that is much more efficient than conventional photoconduction and could make solar energy harvesting and optoelectronic devices far better in the future.

The key to this new method centers on plasmonic nanostructures. These materials are fabricated from gold particles and light-sensitive molecules of porphyin. They're all of precise sizes and arranged in specific patterns. Plasmons, or a collective oscillation of electrons, can be excited in these systems by optical radiation and induce an electrical current that can move in a pattern determined by the size and layout of the gold particles, as well as the electrical properties of the surrounding environment.

These materials can enhance the scattering of light, which means they have the potential to be used to advantage in a range of technological applications. They could even increase the absorption in solar cells. This, in turn, would have enormous implications for solar energy.

This wasn't the first time that the researchers touched on this discovery, though. Back in 2010, the scientists reported the fabrication of a plasmonic nanostructure. Designing the material with a technic known as ferroelectric nanolithography, the researchers couldn't prove that the improved transduction of optical radiation to an eelectrical current was due to the "hot electrons" produced by the excited plasmons.

In order to better understand the mechanism of the plasmon-induced current, the researchers varied the different components of the plasmonic nanostructure; they changed the size of the gold nanoparticles, the size of the porphyin molecules and the spacing of those components. They designed specific structures that ruled out the other possibilities so that the only contribution to enhanced photocurrent could be from the hot electrons harvested from the plasmons.

"In our measurements, compared to conventional photoexcitation, we saw increases of three to 10 times in the efficiency of our process," said Dawn Bonnell, one of the researchers, in a news release. "And we didn't even optimize the system. In principle you can envision huge increases in efficiency."

The findings could have enormous implications for devices in the future. The technology could power everything from laptops to communication devices.

The findings are published in the journal ACS Nano.