In Germany, around 10,000 tons of silicon in old photovoltaic modules end up on the recycling market every year. From 2029, this figure will rise to several 100,000 tons per year. Currently, only the aluminum, glass and copper of old modules are recycled, but not the silicon solar cells.
Researchers at the Fraunhofer Center for Silicon Photovoltaics CSP in Halle (Saale) and the Fraunhofer Institute for Solar Energy Systems ISE have developed a solution together with Reiling GmbH & Co. KG, Germany's largest recycling company for PV modules, to enable this material to be reused: The silicon from the modules was recycled on an industrial scale and used to produce new PERC solar cells.
A working group at the Fraunhofer CSP has therefore developed a process with Reiling GmbH & Co. KG, funded by the Federal Ministry for Economic Affairs and Climate BMWK, with which the silicon can be recovered. This makes it possible to recycle all crystalline silicon PV modules. Prof. Dr. Peter Dold, project manager at Fraunhofer CSP: "It was important for us to develop a scalable process that also makes economic sense. (...) Our new process should prove itself in practice for the recycling industry."
For the process, the solar cell fragments are separated and collected from by-products of the already established mechanical treatment process. The purified silicon is processed into monocrystalline or quasi-monocrystalline ingots in standard processes and then further processed into wafers. Crystallization is carried out with 100 % recycled silicon without commercially pure silicon. The wafers were processed into PERC solar cells at Fraunhofer ISE's PV-TEC, with a cell efficiency of 19.7 percent in the first test. "This is below the efficiency of today's premium PERC solar cells with an efficiency of around 22.2 %.
