Lead Halide Ligand Recycling Enables Low-Cost Infrared PbS Quantum Dot Solar Cells

Large-scale fabrication of PbS quantum dot (PbS QD) solar cells is hindered by the prohibitive cost of the chemicals. Most of these substances and chemicals are employed in the ligand exchange step, more specifically, in lead halide-based ligands. In this study, we investigate ligand recycling. Lead halide ligands are normally employed in PbS solar cells via a solution phase transfer exchange method. The chemical analysis, such as X-ray photoelectron spectroscopy (XPS), demonstrates that both the recycled and fresh lead halide ligands are similar. By employing this recycled ligand in solar cell fabrication, power conversion efficiencies (PCEs) of 10.36 and 10.05% were achieved by using the first and second cycles of the lead halide ligand. After four rounds of ligand recycling, the large-size nanomaterial (1300 nm excitonic peak) solar cells still achieved a PCE of around 9%. The above reclaimable ligand approach can also be extended to small nanomaterials (an exciton peak at around 940 nm). It could obtain a PCE of 10.13 and 9.70% based on the fresh and recycled ligands, respectively. The present recycling ligand work builds a revolutionary strategy for PbS QD optoelectronic devices to decrease costs, production times, and environmental effects through recycling.