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High-purity silicon accounts for as much as 40% of the total cost of solar cells. How to use the minimum amount of silicon to achieve maximum efficiency has become a top priority for solar cell production. Academician Chen Gang of the American Academy of Engineering and professor of the Department of Mechanical Engineering at MIT found a new method that can reduce the thickness of silicon wafers by more than 90% while maintaining high efficiency.
The working principle of silicon solar cells can be divided into two major steps: the first step is to absorb the injected photons, the second step is to stimulate their own electrons. Many research teams have proposed ways to increase the ability of silicon crystals to absorb photons, but these methods also increase their own surface area, which may cause the excited electrons to be recombined into the silicon plate.
The research team headed by Chen Gang tailored the structure of the silicon crystal surface to an “inverted pyramid†type. The diameter of each inverted pyramidal groove is no more than 1 micron. This special "fabric" structure only increases the surface area of ​​ultra-thin silicon crystals by 70%, and the photon absorption capacity is comparable to that of a conventional silicon crystal 30 times thicker. Related research papers were published in the June 2012 issue of Nano Letters. The first author of the paper was postdoctoral researcher anastassios mavrokefalos.
This special “fabric†structure merely increases the surface area of ​​ultra-thin silicon crystals by 70%, while the photon absorption capacity is comparable to that of conventional silicon crystals that are 30 times thicker.
This technology greatly reduces the use of high-purity silicon while ensuring the efficiency of silicon crystals. Not only is it expected to significantly reduce production costs, but it will also reduce the weight of the battery, further reducing the cost for support and installation. At the same time, the preparation of this new type of crystal does not require any new equipment and new materials other than existing silicon wafers, and it is easy to realize scale production in the future.
The next step for the research team is to equip a true photovoltaic cell and prove its efficiency. Chen Gang told the MIT press office that if all goes well, the system is expected to develop commercial products in the near future.
Cui Wei, an associate professor of materials science and engineering at Stanford University, highly evaluated this research by Chen Gang and his colleagues. He said that this is an effective structure for solar cells to absorb photons, "having very considerable potential application value."
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