Leaching and re-synthesis of CIGS nanocrystallites from spent CIGS targets

The original target utilization is only about 30% in the CIGS (Cu(In, Ga)Se2) thin film solar cell sputtering process. The remaining 70% of the target must be recycled to achieve sustainable use of the rare metals, In, Ga, and Se. It is therefore very important to establish spent CIGS target recycling technology to reduce environmental damage. High CIGS recovery was obtained in this study by autoclave leaching CIGS powder in a sulfate solution using H2O2 as the strong oxidant. The CIGS leaching mechanism was studied using XRD and SEM. H2O2 was first adsorbed onto the CIGS surface. Then copper–selenium compound was formed on the CIGS surface. The copper–selenium compound decomposition is the rate-controlling step in the CIGS leaching process. Nearly complete CIGS dissolution can be obtained by autoclave leaching at 140 °C for 4 h using 3 M H2SO4 as the leaching agent and H2O2 as the oxidant. In this study, a direct recycling process combining leaching process and re-synthesis of CIGS nanoparticles was developed to recover CIGS materials for reinsertion into the CIGS supply chain. Mono-dispersed CIGS nano-particles with the mean particle size of 9 nm can be obtained using spent CIGS target as raw materials.