Membrane separation of dispersion of PbS colloidal quantum dots with iodide ligands

• Membrane separation of iodide-ligand colloidal quantum dots (I-CQDs) was first achieved. • The key to successful membrane separation of I-CQDs was solvent design. • The adsorption of I-CQDs to the membrane was controlled by Hansen solubility parameters. • Membrane separation will significantly reduce the production cost of I-CQDs. We have succeeded in membrane separation to classify PbS colloidal quantum dots (CQDs) with iodide ligands, which have the potential to significantly improve the performance of many optoelectronic devices such as solar cells. CQDs are expected to be applied in various fields due to their unique features; however, a method for mass-producing uniform CQDs has not yet been established, and the high manufacturing costs resulting from small-scale production are hindering social implementation. We have proposed the membrane separation process as an alternative to conventional centrifugation and demonstrated an acceleration and improved efficiency of the separation processes, thereby eliminating the bottlenecks. Size separation of CQDs with iodide ligands (I-CQDs) using membrane filtration has remained particularly challenging due to their inevitable adsorption to the membrane. In this work, I-CQDs were successfully withdrawn to the filtrate without adsorption by dispersing them in a quaternary mixed solvent that satisfies the adsorption-inhibiting conditions proposed in previous studies, which are based on Hansen solubility parameters. Our membrane separation technology will become the basis for the low-cost production of I-CQDs.