A composited colloidal Si nanocorals (NCs)/PbS quantum dots (QDs) p–n active layer was demonstrated to have the potential to reduce the surface recombination velocity and further improve the cell efficiency, not only due to the light trapping structure of Si NCs, but the ability of passivation as well as down-conversion in PbS QDs. An appropriate length of Si NCs was acquired first by investigating the interaction of light absorption and effective minority-carrier lifetime. After the integration with PbS QDs, the composited solar cell showed a 30% increase in power conversion efficiency (PCE), compared to its bare Si substrate counterpart. Thus, we believe that the Si NCs and PbS QDs composited structure is promising for the enhancement of the PCE of current Si based photovoltaic devices.