Scientists have discovered that gold electrodes can function as chemical catalysts during the production of black silicon used in solar cells. The discovery will be able to upgrade and optimize the process of preparing solar cells.
![An electron microscope image from a previous study showing the nanoscale ridges that make up the surface of black silicon used in the production of solar cells. [Courtesy of Barron Group/Rice University]](https://www.hayadan.org.il/images/content3/2015/06/SOLAR-1-RN.jpg)
Scientists have discovered that gold electrodes can function as chemical catalysts during the production of black silicon used in solar cells. The discovery will be able to upgrade and optimize the process of preparing solar cells.
Rice University scientists have found a way to optimize the production of solar cells by using an electrode as a chemical catalyst that converts regular silicon into black silicon which is a valuable material. The findings of the research led by chemist Andrew Barron were published in the scientific journal Applied Materials and Interfaces.
Black silicon is silicon with a particularly rough surface that includes ridges or holes that are smaller than the wavelength of light. The rough surface allows efficient collection of light rays from any angle, at any hour during the day. The research team has been trying to optimize the production of black silicon for some time, with advances in the production method potentially bringing the commercialization of this material closer to the preparation of solar cells. One of the research partners explains: "First, reducing the number of steps in a chemical or industrial process is always a good result. Secondly, this is the first time that a metal functions as a chemical catalyst for a reaction that takes place a few millimeters from it."
The lead researcher points out that the metal layer used as the top electrode is produced at the last step in the manufacturing process of a solar cell. The new method, known as "contact-assisted chemical etching", places the thin gold layer that functions as the electrode at an earlier stage in the process, which eliminates the need to remove spent catalyst particles. The researchers discovered that the digestion process inside a chemical bath takes place away from the gold layer. This distance, explains the lead researcher, seems to be related to the semiconductor properties of silicon.
"One of the researchers performed the reaction with gold contacts while adding a silver or gold catalyst. In the next step I asked him to perform the same reaction without the catalysts and suddenly we got black silicon - however, such that the embryo can only eat at a certain distance from the contacts. And no matter what we did - this distance remained constant," said the chief researcher. "This result means that the electrochemical reaction occurs at the metal contacts and at the position of the silicon at a certain distance from the contacts," notes the lead researcher. "The distance depends on the charge carrying capacity, that is, the conductivity, of the silicon. At a certain point, the conductivity is no longer sufficient to move the charge an additional distance."
The researcher explains that an extremely thin layer of gold placed over titanium, which binds well to both gold and silicon, will serve as both an efficient electrode and a chemical catalyst. "The trick is to cut the layer deep enough to avoid the reflection of the light rays, but not too deep so as to cause a short in the cell's electrical circuit," explains the lead researcher. The researchers note that the electrode's ability to function as a chemical catalyst may lead to more efficient and cost-effective electronic component manufacturing processes.
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