According to experts, conventional solar cells are made from silicon wafers, which are around 1/3 of a millimetre thick and the top surfaces are covered with pyramids around 10 microns high. The pyramids reduce the reflection from the top surface and trap the light inside the solar cell. To reduce the cost of solar cells, thin film solar cells are being developed, which are only a few microns thick and have the potential to be much cheaper than conventional solar cells, as they are made from semiconductor materials like amorphous silicon or cadmium telluride rather than silicone.
Pyramid textures can't be applied to these cells, so new structures are needed as the cells are thinner than the wavelength of incoming light which is long and is less likely to be absorbed and converted. Consequently thin-film photovoltaics convert 8 to 12 percent of incoming light to electricity and crystalline silicon converts 14 to 19 percent.
Kylie Catchpole, currently a research fellow at the Australian National University in Canberra, began working on this problem in 2002 at the University of New South Wales in Sydney. "One of the things I came across was plasmonics--looking at the strange optical properties of metals," she says.
Plasmons are a type of wave that moves through the electrons at the surface of a metal when they are excited by incident light and Catchpole found that nanoparticles of silver she deposited on the surface of a thin-film silicon solar cell did not reflect back light that fell directly onto them, as would happen with a mirror. Instead, plasmons that formed at the particles' surface deflected the photons so that they bounced back and forth within the cell, allowing longer wavelengths to be absorbed.
Catchpole's experimental devices produce 30 percent more electrical current than conventional thin-film silicon cells. If she is able to integrate her nanoparticle technology with the processes used to mass-produce thin films commercially, thin-film photovoltaics could not only gain market share but could sustain growth in the solar industry overall.
Catchpole wants to refine the technology further before commercializing it.
Credit: Australian National University, MIT Review
Top image of Kyle Catchpole source University of New South Wales
For more read : Energy Harvesting and Storage for Electronic Devices 2010-2020
