PERC solar cells made from recycled silicon
Several startups and initiatives in Germany and Europe have already begun recycling valuable raw materials such as aluminum, glass, and copper from old photovoltaic modules. This is because according to current estimates, the amount of discarded solar modules in Germany alone will increase to over 100,000 tons annually by the end of the 2020s. (pv-magazine, 11/10/2021)
The Fraunhofer Center for Silicon Photovoltaics CSP and the Fraunhofer Institute for Solar Energy Systems ISE, together with the module recycling company Reiling, have now developed a method for processing the silicon of old crystalline solar modules on an industrial scale so that it can be reused to manufacture new PERC solar cells. There is to be no restriction to specific manufacturers: "It was important to us to develop a scalable process that also makes economic sense," emphasizes Peter Dold, project manager at Fraunhofer CSP. "Many things are possible in the lab, but our new process should prove itself in practice for the recycling industry." (pv-magazine, 2/8/2022)
For the process, solar cell fragments are collected from byproducts of the already established mechanical reprocessing process. At Fraunhofer CSP, these 0.1 to 1 millimeter fragments are freed from plastic and glass by various sorting processes. Afterwards the backside contact, silver contacts, anti-reflective layer and emitter are removed step by step by wet chemical etching. From the processed silicon, monocrystalline or quasi-monocrystalline ingots are produced, which are further processed into wafers. Crystallization is performed with 100 percent recycled silicon without the addition of high-purity silicon. In an initial test run, the recycled PERC solar cells had an efficiency of 19.7 percent. By comparison, the average efficiency of new premium PERC solar cells is around 22 percent.
Sources:
pv-magazine, article by Petra Hannen (8.02.2022):
https://www.pv-magazine.de/2022/02/08/fraunhofer-ise-fertigt-perc-solarzellen-aus-recyceltem-silizium-mit-197-prozent-wirkungsgrad/, accessed: 2/9/2022 at 11:15 a.m.
pv-magazine, article by Petra Hannen (11/10/2021):
https://www.pv-magazine.de/2021/11/10/solar-materials-will-rohstoffkreislauf-von-photovoltaik-modulen-schliessen/, accessed: 2/9/2022 at 11.40 a.m.