Shockley-Queisser Limit

Ever since the industrial revolution, humanity has continued to increase energy consumption. Coal and oil are, of course, the most commonly used to meet the high demand followed by natural gas. Solar energy has the more potential than any other source, yet it is the source of so little of total energy produced. Fossil fuels will be exhausted first in less than 300 years (4), then natural gas. Solar power could provide unlimited pollution free energy. The greatest challenge in this endeavor is in increasing the efficiency of solar cells. The Shockley-Queisser limit is the theoretical maximum efficiency limit of a solar cell and is approximately 34%. It was first calculated by William Shockley and Hans Queisser in 1961 (6). The reason for the limit is because until recently one photon could only excite one electron while excess energy was given off as heat. However, a research project at the Massachusetts Institute of Technology has developed a technique called single exciton fission. The process has not been perfected, but this technique has the potential of allowing silicon solar cells to have over 30% efficiency (1) and possibly overcome the Shockley-Queisser limit. The process has not been perfected and there are many issues with the technique. …show more content…
While silicon based solar cells are the more popular, recent gallium arsenic (GaAs) based cells have been found potentially have the highest efficiencies out of any single-junction solar cells. These cells have been steadily increasing their efficiency rates. This may be due to high quality materials though. GaAs cells often include thin submicron absorbers, smooth planar surfaces, and level backside mirrors in an attempt to minimize radiative recombination and maximize collection of photon. It is a delicate balance and difficult to achieve. To reduce the commercial price of these solar cells, a way must be created to easily produce the necessary quality of