New Nanowire Template for Improved Solar PanelsCategory: Science & Technology
Posted: June 20, 2012 11:48AM
The photoelectric effect is a special interaction between electrons and photons. When a photon with the correct frequency strikes an electron, the photon and its energy can be absorbed by the electron, causing it to jump to a higher energy level around the atom. If there is enough energy, the electron will escape the atom completely. By forcing these escaped electrons through a circuit before they can return to an atom, we can convert solar energy to electrical energy. This is how solar panels work and while the system seems very efficient, there are some issues with it.
The Shockley-Queisser, or SQ limit is the maximum efficiency achievable by a semiconductor-based solar panel, and is roughly 35%. There is no way to get out more than 35% of the energy in a certain frequency range using solar panels. For silicon this is a real issue because the frequency range it responds to is limited, but other semiconductors can have their range extended, allowing more light to be absorbed and more energy to be produced. One of these other semiconductors is indium gallium nitride and researchers at Sandia National Laboratories have found a way around one problem with it. The amount of indium in the material controls the frequency range of the semiconductor, but while adding more indium can increase the range, it also makes the material more stressed and likely to break.
The researchers decided to try making an indium gallium nitride solar panel on an array of nanowires, instead of the usual flat substrate. This allowed the material to relax and support a mixture that is roughly one third indium, which is more than the previous record. This successfully increased the range of frequencies the material will react to, but the design itself will need some improvements. At just 0.3% efficiency, this is far from the current 15% achieved by many other designs. Still, this shows it is possible to increase the amount of indium in the mixture, which will increase power output.