A new technology that could bring an increase in solar cell efficiency has been presented by Purdue researchers. They use an ultra-fast pulsing laser which creates “microchannels” needed to connect the solar cells in series, for building a usable system.
The method commonly used nowadays is mechanical, making use of a stylus that “scribes” onto the layer, but the results are far from perfect, often with high irregularities which lower the conversion efficiency sensibly. The process is also expensive.
“It creates very clean microchannels on the surface of each layer,” Shin said. “You can do this at very high speed, meters per second, which is not possible with a mechanical scribe. This is very tricky because the laser must be precisely controlled so that it penetrates only one layer of the thin film at a time, and the layers are extremely thin. You can do that with this kind of laser because you have a very precise control of the depth, to about 10 to 20 nanometers.”
The depth is controlled by throwing ultra-short laser shots of about 1 picosecond. If they would have approached this with a normal laser, then the thin film solar cells they would have tried to etch would have been completely melted, but this method proves both ultra-exact and fast. More precisely, it is able to scribe a few meters per second, unlike the mechanical approach.
“The efficiency of solar cells depends largely on how accurate your scribing of microchannels is,” said Shin Cheng, one of the research leaders. “If they are made as accurately as possibly, efficiency goes up.”
Being awarded a three-year, $425,000 grant from the National Science Foundation, the project has realistic chances of succeeding and increasing solar cells’ efficiency by tweaking other aspects than the direct conversion process.