Hybrid Ketone‐Mediated Purification Enables Ligand Preservation for Efficient PbS Colloidal Quantum Dot Optoelectronics

Colloidal quantum dots (CQDs) are promising absorbers for infrared optoelectronics, and their performance and stability are influenced by surface ligand chemistry. Herein, we tailor the antisolvents via a Hansen solubility parameter (HSP) to induce sufficient precipitation while minimizing surface ligand loss during CQD purification process. By redefining the interaction radius ( R o ) as an effective purification boundary, we find that a hybrid ketone antisolvent combination, an acetone/MEK (AMK), is positioned near this boundary in HSP space. As a result, PbS–AMK preserves surface‐bound ligands more effectively than PbS–ethanol counterparts, maintaining CQD monodispersity and improving long‐term stability. Devices fabricated from PbS–AMK exhibit smaller photovoltaic degradation during CQD aging, with only a 7.81% reduction in power conversion efficiency compared to 25.9% for PbS–ethanol. In addition, the PbS–AMK devices achieve 3.4‐fold higher specific detectivity under SWIR photodetection operation.