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Studies have shown that light absorbed on the surfaces of silicon wafers on solar cells absorbs holes and spikes. In experiments conducted by scientists at Rice University, gold played a dual role in black silicon, one as an electrode, and the other as a catalyst to etch the surface of a silicon wafer within minutes.
Researchers at Rice University have discovered a new method to increase solar cell production efficiency by using top electrodes as catalysts to convert pure silicon into valuable black silicon.
The chemist Andrew Barron of the Labs lab published the study on the materials used and published on the Journal of the American Chemical Society.
Black silicon is a type of silicon with a highly deformed surface that has many nanometer-scale peaks or holes that are smaller than the wavelength of visible light. This structure can effectively absorb visible light at any time and any angle of the day. Barron and his team have been studying the process of improving the production of black silicon for some time. According to him, the progress in the preparation process should be able to further advance the commercialization process.
Barron said that the new study conducted by Rice University postdoctoral researcher Yen-Tien Lu has two highlights. First of all, simplifying the complicated process is a very good initiative. Second, this is the first time that metal is used as a reaction catalyst at a distance of a few millimeters.
Barron said that in the manufacture of solar cells, metal layers are often used as top electrodes. A well-known new method is contact-assisted chemical etching. This new method is applied to the arrangement of thin gold wires, whereas in the conventional method, gold is used only as an electrode. This method also does not require removal of the reacted catalytic particles.
The researcher discovered that in the chemical bath, the etching reaction occurred at a certain distance from the gold line. Barron said that this distance may be related to silicon semiconductor performance.
According to Rice University's research in the preparation of black silicon wafers for solar cells, the gold electrode also acts as a catalyst. Black silicon basically does not reflect light, and it allows more light and active components in solar cells to be converted into electricity.
Barron said: “Yen-Tien was studying the reaction of the top gold electrode, adding gold or silver catalysts and getting these beautiful images, and then I said 'OK, now we're going to carry out the reaction research without catalysts'. Surprisingly We got black silicon, but the etching reaction can only occur at a distance from the contact layer, and no matter how we deal with it, this distance always exists.
Barron said: “This phenomenon tells us that the electrochemical reaction takes place at a distance from the contact layer between the metal and the silicon wafer. This distance depends on the carrier transport and conduction capability of the silicon. In some cases, the conductivity is not sufficient to make The carrier travels further.
Barron said that a very thin layer of gold is placed on titanium. This structure is very good in combination with gold and silicon, and it should be able to be an effective electrode and also be used as a catalyst. He also said: "This technique must etch deep enough trenches to eliminate reflections from the sun. If the trench is not deep enough, it will cause the battery to short circuit.
This electron micrograph was from an earlier study showing nanoscale spikes on the black silicon surface in solar cells.
Barron considers the catalytic ability of the electrode to show that other manufacturing processes for electronic products can benefit from it.
Barron said: "The metal bonding layer is usually placed last, which raises some questions for our process. Can we put the bonding layer early? Can we perform chemical reactions at other times during the manufacturing process?"
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