End-of-life CIGS photovoltaic panel: A source of secondary indium and gallium

The photovoltaic market has boomed in the last decade, and it is becoming much richer of high performance technologies. The copper indium gallium selenide (CIGS) panel represents an example of young technology that shows high energy efficiency, kept at extreme weather conditions. Its average lifetime is around 25 years, and a strategy for a convenient recycling should be planned to prevent the future storage of high waste amount. The interest of end-of-life CIGS panels is due to their content of critical raw materials, mainly Ga and In, with concentrations around 600 and 90 ppm, respectively, higher than those in the ores. In this context, we tested different leaching agents (H2SO4, HCl, HNO3, citric acid, and NaOH), in the possible presence of a mobilizing agent (H2O2 and glucose), to obtain high-efficiency metal extraction. Furthermore, to minimize the environmental impact of the process, the experimental activity was combined with the evaluation of the carbon footprint of the experimented options, using the life cycle assessment tool. Overall, the combination of CA and H2O2 appeared the best choice, from both the operative and the sustainability point of view, showing efficiencies higher than 90%, after 1 hour, at 80 degrees C, with a carbon footprint of 0.1-kg CO2-eq. The obtained result represents an innovation in the field of end-of-life CIGS photovoltaic panel exploitation, and it is the starting point for both secondary In and Ga production, in agreement with the circular economy approach.