Kylie Catchpole (image), from the Australian National University in Canberra, working to make thin film solar cells more efficient, discovered that nanoparticles of silver deposited on the surface of a thin-film solar cell would not reflect the incident light back, but instead it would deflect the photons so they bounce back and forth withing the cell, allowing longer wavelengths to be absorbed.
Thin film solar cells have a lot of advantages to silicon cells, as they are made from relatively cheap semiconductor materials, like amorphous silicon or cadmium telluride, opposed to conventional cells made of thick and expensive wafers of silicon.
Still, thin film solar cells have a drawback: they are less efficient than their silicon counterparts, reaching 12 percent at most, while silicon cells the same size would have up to 19 percent.
Catchpole started to work on thin film solar cells back in 2002 at the University of New South Wales in Sidney. “It was a case of ‘start at the beginning: can you think of a completely different way to make a solar cell?’ ” she says. “One of the things I came across was plasmonics–looking at the strange optical properties of metals.” Plasmons are a type of wave that moves through the electrons at the surface of a metal when they are excited by incident light. Others had tried harnessing plasmonic effects to make conventional silicon photovoltaics more efficient, but no one had tried it with thin-film solar cells.
Her prototype solar cells produce up to 30 percent more current than conventional thin films. If her discovery would be applied to the mainstream industry, it would make thin film the manufacturers’ new best friend, bringing them more sales and higher efficiency for the end user. And, let’s not forget: it would help reducing the carbon dioxide emissions worldwide.
There is one issue, though: tellurium is not present in enough quantities to supply a fully-growing solar cell industry, for making cadmium telluride, and Catchpole admits it: “There just isn’t enough tellurium to make a substantial difference to the way the world’s energy is produced,” she says. “Silicon is the way to go.”
Although approached by numerous companies, Catchpole wants to improve the technology before getting it out on the market.