Microrecycling of waste solar cells via an in-situ fluorine-generating thermal treatment for high purity silicon recovery

With the rapid advancements in photovoltaic (PV) technology over recent decades, the world faces a growing number of obsolete solar panels, imposing substantial environmental and economic challenges globally. This study demonstrates a method for isolating valuable metals, including Si, Ag, and Sn, from end-of-life solar cells, through a medium-temperature in-situ F-producing thermal treatment at 550 °C followed by a chemical etching process. The thermal treatment led to (I) the formation of uniformly distributed Sn-Pb alloy submicron particles on the Si wafers' surface, and (II) in-situ generation of F and a significant increase in the concentration of F atoms (by decomposition of Polyvinyl fluoride (PVF) back sheets) on the wafers' surface up to 300 nm. The infiltration of submicron particles and F atoms enabled the microrecycling of the cells by diminishing the TiO 2 corrosion-resistant layer atop the Si wafers. The subsequent two-step etching, using a basic solution, firstly removed Al impurities within 3 min and facilitated the liberation of 70 wt% of Ag strips from the wafers while avoiding Si loss. The remaining Ag and Sn were extracted using the second etching stage via an acidic media. The resulting purified Si wafers, with a high purity of 99.7 wt%, were then used to produce β-SiC. This SiC possessed mixed sub-micron particles, nanoparticles, and nano-whiskers coated with a SiO 2 shell of thickness 2–3 nm, which is suitable for microwave absorption applications. The microrecycling method presented in this study offers a sustainable path toward minimizing waste in recycling spent photovoltaic solar cells.