Solar technology is evolving and the latest developments have concentrated on making old technology more efficient. But solar industry observers are always looking for that game-changer that may thrust solar into the mainstream more quickly than simply with incremental efficiency improvements. Stanford researchers recently published a paper that describes a new technology that may portend fundamental changes in solar energy applications.
According to the Stanford Daily, Stanford researchers Shanhui Fan, Zongfu Yu and Aaswath Raman took a significant step toward future solar power practicality with a September 27 paper entitled "Fundamental Limit of Nanoscale Photonic Light Trapping in Solar Cells," which lays the foundation for nanoscale solar cells research. The title may not get you excited, but the implications for the solar industry could be far and wide.
Solar panels used in house are crystalline panels which are thick, heavy, and require large spaces. However, this new solar cells take a fundamentally different approach, using solar cells as thin as 500 nanometers, or one two-thousandth of a millimeter. The senior author of the study, Shanhui Fan, is quoted in an article entitled "Solar Cells Thinner than Wavelengths of Light Hold Huge Power Potential" in the Science Daily: "The longer a photon of light is in the solar cell, the better chance the photon can get absorbed." The research team used a technique called "light trapping," keeping sunlight in the grip of the solar cell long enough to squeeze the maximum amount of energy from sunlight. According to the article, the research shows that "light ricocheting around inside the polymer film of a solar cell behaves differently when the film is ultra thin. A film that's nanoscale-thin and has been roughed up a bit can absorb more than 10 times the energy predicted by conventional theory."
Most solar panels sold today utilize 20th century technology of making thick panels with rough surfaces to keep light rays inside the panel for as long as possible. However, the nanoscale cells that Fan's team researched take a fundamentally different approach. As one member of the research team was quoted in the Stanford Daily article: "Previously, the theory treated light as a straight ray. But light has a lot of wave factors, and this in fact does not show up until you go into the nanoscale."
According to an article in the Environment News Service, the Stanford researchers contend that the solar electric cells built on the nanoscale "have the potential to generate huge amounts of electricity compared to existing solar cells." The benefit from nanoscale confinement is "surprising," because, according to one of the researchers, it overcomes the conventional limit and "opens a new door to designing highly efficient solar cells."
If this new technology is proven and applied commercially, solar panels could be in for a major overhaul. This new technology may be a very important step forward in significantly improving solar panel efficiency and reducing manufacturing costs. In terms of efficiency, instead of absorbing light, like traditional thin film applications, nanotech thin film scatters light and reflects it. Thin film is much more flexible than the crystalline modules currently available.
Manufacturing costs could also drop. As the Science Daily article points out, these nanoscale cells can be manufactured with organic materials in chemical reactions in solution," rather than needing high-temperature or vacuum processing, as is required for silicon manufacture." The material costs are much lower than if the cells were built around bulky silicon. It may be awhile before nanoscale thin film is commercially available, but it definitely has the potential to change the game.