How to make a more durable and more efficient self-cooling solar cell? The answer is to add a thin layer of glass surface. Solar cells can convert solar radiation into electric energy, but in this process of energy transformation there is great energy loss, among which the energy consumption caused by solar cells overheating is so huge that it not only restricts the photoelectric conversion efficiency of cells, but also reduces their lifetimes.
Researchers at Stanford University cover a thin layer of quartz glass with tiny cone and pyramid structures on the surface of a silicon solar cell, and they find that this method can considerably lower the cell’s operating temperature thus weakening the “overheating” effect. Then, these researchers observe that this layer of rugged quartz glass can reflect the excessive thermal radiation, and by eliminating the excessive infrared radiation, the solar cell can keep an appropriate temperature, thus improving its photoelectric conversion efficiency. If its temperature rises, the open-circuit voltage will fall dramatically, consequently lowering the cell’s photovoltaic performance. Although the current will rise slightly at the moment, it is not worth mentioning compared to the efficiency that may be lowered otherwise.
Researches show that the upper limit of a single silicon solar cell’s energy conversion efficiency is 33.7%, and its efficiency will drop by 0.5% with one degree centigrade of temperature rise. In this way, the cell’s energy conversion efficiency decreases with the rise of its temperature, which is similar to other kinds of solar cells. At present, the major ways to cool cells such as installing ventilation devices and using liquid coolants have the problem that their costs outweigh their benefits, so they still can not effectively solve the energy loss caused by the overheating. Then, this research finding may help to develop a more efficient solar cell.
This kind of more efficient solar cells may become one of the strong competitors to substitute for fossil fuels in the future. this rugged glass surface works by using lights with different wavelengths in the solar radiation. In the spectrum, visible lights carry more energy, while the infrared light carries more heat. Researchers find through calculations that while the quartz glass surface is reflecting the infrared light, it does not affect the cell’s absorption of visible lights. Then they combine the glass surface containing silicon micro-pyramids with the solar cell, or directly integrate them to cool the solar cell to the limit of its capacity. In this way, the appropriate operating temperature can significantly extend the cell’s lifetime, thus reducing its cost on the other hand.
However, there are some different views from the scientific community, as some scientists think that, although this research has a solid theoretical foundation, it may not be easy to be applied in practice. Nevertheless, researchers have started to study the practical application of this finding. And they have verified its design with an accurate numerical method, and are making their efforts to demonstrate the feasibility of their first prototype.