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A proof of concept for an innovative production line for silicon solar cells with a double-than-usual throughput of 15,000 to 20,000 wafers per hour has been developed by the Fraunhofer Institute for Solar Energy Systems ISE, a consortium of plant manufacturers, meteorology companies, and research institutions.
The researchers implemented new on-the-fly laser equipment, which continually processes the wafers as they move at high speed under the laser scanner. For the metallization of solar cells, the consortium introduced rotary screen printing and replaced the current standard process of flatbed screen printing.
The Fraunhofer researchers integrated the two separate processes of diffusion and thermal oxidation of wafers into one. Wafers were no longer placed individually but stacked on top of each other to be processed in the furnace. The oxidation process then created the final doping profile and achieved surface passivation simultaneously, thereby increasing the throughput of the process by a factor of 2.4.
Following the electrode imprint on the solar cells, the contact of the electrodes to the silicon solar cell is formed on both sides in inline furnaces. A belt with a three times faster speed was installed in the furnace, and it could significantly increase throughput while not compromising the efficiency of the solar cells.
The consortium devised two concepts to characterize the complete solar cells. A contactless method for which a patent has been filed and a method using sliding contacts was implemented to enable future production lines to test cells faster. This made 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,” said Florian Clement, project manager at Fraunhofer ISE.
Recently, a team of scientists found that inserting a metal fluoride layer on multi-layered perovskite-silicon tandem solar cells can stall charge recombination and enhance performance.
In February, ISE researchers, in partnership with Reiling GmbH, developed a solution to recycle discarded modules on an industrial scale and reuse them to produce passivated emitter and rear contact (PERC) solar cells.