In this paper, core–shell quantum dots (QDs) with two polar surface functional groups (ZnSe/ZnS–COOH QDs and ZnSe/ZnS–NH2 QDs) are synthesized in an aqueous phase. Photoluminescence (PL) and absorption spectra clearly indicate luminescence down-shifting (LDS) properties. On the basis of QDs, surface functional group multilayer LDS films (M-LDSs) are fabricated through an electrostatic layer-by-layer (LBL) self-assembly method. The PL intensity increases linearly with the number of bilayers, showing a regular and uniform film growth. When the M-LDS is placed on the surface of a Si-based solar cell as an optical conversion layer for the first time, the exteal quantum efficiency (EQE) and short-circuit current density (Jsc) notably increases for the LDS process. The EQE response improves in a wavelength region extending from the UV region to the blue region, and its maximum increase reaches more than 15％between 350 nm and 460 nm.