The goal at the end of the rainbow is to capture the pot of gold. In the case of solar PV, it is to increase the efficiency of light-to-electricity conversion. A scientist at MIT, Dr. Peter Bermel has a totally new concept of increasing the conversion process. He and his colleagues have invented a way of concentrating the energy in the sun’s rays without the need for mirrors. It is, quite literally, a suntrap. Their concept has been published in in Nanoscale Research Letters and is had to describe. The following is a story taken from The Economist dated December 31, 2011.
Dr Bermel’s proposed trap is a thin sheet of tungsten (a heat-resistant metal) that has been processed in quite a complicated way. One surface, which faces the sun, is covered in microscopic pits. The other, which faces a specialized type of solar cell made of a material called indium gallium arsenide, is sculpted into a structure called a photonic crystal that causes it to emit infra-red radiation selectively at the frequency best absorbed by the cell. Both of these surfaces would be created by photolithography, the process used to make computer chips. According to Dr Bermel’s calculations, would be a system that converts 37% of sunlight into electricity. This compares with a maximum of 28% by standard silicon-based solar cells that have not had the incident light concentrated by parabolic mirrors.