Developing A More Efficient Solar Cell
Originally published on the ECOreport.
The electricity produced by current PV solar installations is not adequate for Germany’s targeted energy transformation. Photovoltaic power will have to go through a ten-fold increase over the next 15 years. This may be possible using a high performance alternative that uses Laser-Fired Contact (LFC) technology. Ralf Preu and Jan Nekarda were awarded the 2016 Joseph von Fraunhofer Prize for developing a more efficient solar cell.
Developing A More Efficient Solar Cell
The back of most solar cells is coated with a wide-surface metallic contact that allows electricity to flow. In its press release, Fraunhofer explained how they could increase efficiency by inserting a very thin non-conductive layer between the cell’s contact layer and silicon wafer:
Acting as a mirror, this layer reflects the share of sunlight not absorbed when penetrating the wafer back into the silicon wafer. Since the front side also reflects this light back into the wafer, it is also captured in the silicon wafer and the efficiency level of the solar cell increases. Drawing the electricity from the wafer requires many small apertures in the non-conductive layer in order to establish contact between the electrode metal and the silicon wafer. The LFC procedure creates each of these approximately 100,000 contacts per wafer with a single laser pulse.
“The challenge was to coordinate the pulses in such a way that contact is completely established, while damage to the silicon is kept to minimal levels. Here it’s crucial that the laser light effect is limited to between 50 and 2,000 nanoseconds,” explains Dr. Jan Nekarda, group manager at the Fraunhofer ISE.
“PERC solar cells made this way have an improved efficiency level of one percent absolute. With today’s solar cell efficiency of approximately 20 percent, that‘s about five percent relative. We gain an additional two percent in the system, which means we increase the overall energy yield by seven percent,” Ralf Preu (Division Director of PV Production Technology and Quality Assurance, at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg) is happy to report.
This 7% increase in yield translates into a decrease in material costs and a 7% reduction in the amount of land needed to produce the same amount of electricity.
Next Evolutionary Stage Of Solar Cell
LFC technology has already gone into production.
“In the current year alone manufacturers have invested more than 200 million euros in the implementation. This finally means the establishment of the next evolutionary stage of the silicon solar cell.”
Hannah Q Cells has manufactured more than 20 million cells.
Image Credits: In order to manufacture high efficiency solar cells in series production, Dr. Jan Nekarda and Dr.-Ing. Ralf Preu (left to right) developed the Laser Fired Contact (LFC) process. ©Fraunhofer ISE
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