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Every year around 10,000 tonnes of silicon end up in recycling plants in Germany.

Concerted efforts are underway in Germany to recycle more and become less dependent on photovoltaic (PV) imports. The Fraunhofer Centre for Silicon Photovoltaics (CSP) and the Fraunhofer Institute for Solar Energy Systems (ISE) have therefore developed a system for reclaiming the silicon from discarded PV modules on an industrial scale in order to reuse the material in PERC (rear cell) solar modules produced domestically.

Every year around 10,000 tonnes of silicon end up in recycling plants in Germany. This figure is expected to rise to several hundred thousand tonnes per year by 2029, as the first wave of PV modules installed twenty years ago come to the end of their lives, or when their feed-in tariff expires. It’s a staggering recycling challenge; especially as only aluminium, glass and copper are reprocessed currently and the silicon cells go to waste.

The Fraunhofer CSP worked with small fragments of silicon cells mechanically extracted during conventional recycling. The silicon elements were then separated from the glass and plastic encasing them and in a further step the contacts, anti-reflective layer and emitter were removed by wet chemical etching. The recycled silicon was processed into crystalline ingots and then into wafers.

In the final demonstration stage, the silicon wafers were made into PERC solar cells in the laboratories of Fraunhofer ISE's PV-TEC. In an initial trial, the solar cell conversion efficiency was 19.7 percent. “This is below the efficiency of today's premium PERC solar cells, which have an efficiency of around 22.2 percent, but it is certainly above that of the solar cells in the old, discarded modules,” says Professor Peter Dold, the project manager at Fraunhofer CSP, in a press release.

The project was fully funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK).