German research institute Fraunhofer Institute for Solar Energy Systems ISE along with industry partners have come up with a proof of concept for an innovative production line with a throughput of 15,000, 20,000 wafers per hour, 'double the usual throughput' with an aim to bring down production time for high efficiency solar cells by half.
Heading a consortium of plant manufacturers, metrology companies and research institutes, Fraunhofer ISE presented details of the research project at the 8th World Conference on Photovoltaic Energy Conversion in Milan, Italy.
Along with doubling production, higher throughput will bring down production costs and alleviate supply bottlenecks, it added, and thereby accelerate the deployment of solar PV.
"In order to deploy more solar installations as quickly as possible and to make our supply chains more robust, Europe should re-establish its own production centers for high-efficiency solar cells," said Division Director of PV Production Technology at Fraunhofer ISE, Dr.-Ing. Ralf Preu. "By boosting throughput and making production technology more resource-efficient, we can cut costs considerably and unlock sustainability potential that we will be able to leverage thanks to process knowledge and engineering excellence."
The team optimized the entire process by investigating every stage of the production of high efficiency solar cells and ascertained that some processes needed to be accelerated and others needed to be reinvented from the scratch. For instance, they introduced rotary screen printing instead of the current standard of flatbed screen printing for metallization of the cells.
At the same time, they implemented a new on-the-fly laser equipment to continue processing wafers as they moved at high speed under the laser scanner.
Another different process they introduced was stacking wafers on top of each other to be processed in the furnace instead of being placed individually with an aim to integrate the diffusion process and thermal oxidization into a single step. This oxidization process creates the final doping profile and achieved surface passivation at the same time. It then increased the throughput of the process by a factor of 2.4.
The team installed a 3 times faster belt speed in the furnace and were able to significantly increase the throughput without compromising the solar cell efficiency.
Further, they used a contactless method (for which Fraunhofer ISE has filed a patent) and a method using sliding contacts to enable future production lines to test cells faster. This process makes it possible to keep up a continuous speed of 1.9 meters per second while measuring the cells, with the team demonstrating great measurement accuracy for both concepts.
"Compared to the numbers we currently see, the production systems developed within the scope of the project achieve at least double the throughput," added Project Manager at Fraunhoder ISE Dr. Florain Clement.