An environmentally friendly method for selective recovery of silver and ITO particles from flexible CIGS solar cells

While the share of solar energy harvesting by photovoltaic (PV) systems in electricity production increases, their recycling still remains mainly at an early stage. Therefore, valuable and critical elements like silver (Ag) and indium (In) are lost along with production and end-of-life waste, highlighting the need for simple and sustainable recycling solutions which could be easily implemented by the industry. In this paper, we suggest a simple environmentally friendly method for selective recovery of Ag and Indium Tin Oxide (ITO) particles from flexible Copper Indium Gallium diSelenide (CIGS) solar cells, using two-step ultrasonic (US) leaching with low nitric acid (HNO3) concentration of 0.1 M. The first step aimed at the selective liberation of ITO through the selective dissolution of the zinc-rich layer underneath, using low US power for 3 min. In the second step, the same conditions as in the first step were applied, but now using high US power for 15 min for removal of the Ag grid lines. Both the ITO and the Ag grid particles were subsequently recovered by filtration and there was no loss of Ag observed in the leachates. By this method, a complete separation of ITO and Ag from the solar cell was achieved, with no changes in their crystal structure and promising purities of about 70.5 wt% and 95.0 wt%, respectively. This new approach opens up a new path for possible direct reuse of these materials in the manufacturing of new PVs, after further purification, with an impressively low need for chemicals.