Direct Recycling of Silver and Silicon from Solar Cells through Selective Alkaline Etching

Recycling retired silicon solar cells is indispensable to sustain the ever-increasing deployment of photovoltaic (PV) panels. However, the recycling of silver (Ag) and silicon (Si) remains a challenge because the use of toxic acids (e.g., HF, HNO₃) results in serious environmental burdens. Herein, we report a selective alkaline etching approach for the separation of Ag from Si solar cells, achieving complete separation in 5 min. The separation of Ag and Si is realized by the selective etching of SiO₂ and Si at the Ag/Si interface in the NaOH solution, where Ag is insoluble and collected as Ag wires. The recovery rates of Ag and Si reach 99% and 95%, respectively. Unlike traditional methods, Ag is directly recovered without the complex dissolution-electrolysis process. Si is recovered rather than fully or partially dissolved in the hydro-metallurgical process or converted into slags in the pyro-metallurgical process. Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) results show that this approach has environmental and economic benefits. Overall, the selective alkaline etching approach is a green and low-cost recovery method to recycle Ag and Si, which will close the materials circle for the PV industry.