Scientists from Ural Federal University (UrFU) in Yekaterinburg, Russia, have developed a new technology for processing silicon wafers that could improve the light absorption of silicon solar cells over a broad spectral range.
Described in Materials, the new process, known as hybrid chemical and laser texturing, treats a silicon wafer with a femtosecond laser beam following exposure to various chemical reagents. The pre-chemical etching enables the laser treatment to be performed five-times faster.
Ultrafast lasers are being increasingly used to produce nano- and microstructures on a wide range of surfaces, granting them different functional properties. For example, surfaces can be made to be superhydrophobic/hydrophilic, corrosion resistant, or in the case of solar cells, more light absorbent (the reflection coefficient of the silicon wafers is significantly reduced). The latter is what is being used by the researchers to increase the efficiency of photovoltaics.
"Currently, the formation of light-absorbing micro-reliefs on the surface of silicon wafers is achieved by a chemical process that is relatively inexpensive and used on an industrial scale,” said Vladimir Shur, Director of UrFU’s Modern Nanotechnologies Ural Multiple Access Center. “However, after chemical treatment, the wafers have a significant reflection coefficient, which reduces the efficiency of solar cells. An alternative method is laser treatment of the wafers. It reduces the reflection, but requires a significant amount of time using a femtosecond laser. Our proposed laser treatment after chemical etching reduces the processing time by a factor of five. At the same time, the reflection coefficient of wafers processed by the hybrid method is 7-10% lower than after chemical treatment,"
The research was carried out with the partial financial support of the Ministry of Higher Education and Science of the Russian Federation under the development programme "Priority 2030". It could also have implications in biomedicine for producing highly sensitive sensors for DNA analysis and detection of viruses and bacteria.