Solution-Processed, Ultrathin Solar Cells from CdCl3–-Capped CdTe Nanocrystals: The Multiple Roles of CdCl3– Ligands

Solution-processed CdTe solar cells using CdTe nanocrystal (NC) ink may offer an economically viable route for large-scale manufacturing. Here we design a new CdCl3–-capped CdTe NC ink by taking advantage of novel surface chemistry. In this ink, CdCl3– ligands act as surface ligands, sintering promoters, and dopants. Our solution chemistry allows obtaining very thin continuous layers of high-quality CdTe which is challenging for traditional vapor transport methods. Using benign solvents, in air, and without additional CdCl2 treatment, we obtain a well-sintered CdTe absorber layer from the new ink and demonstrate thin-film solar cells with power conversion efficiency over 10%, a record efficiency for sub-400 nm thick CdTe absorber layer.