Nanostructured silicon (Si) can provide improved light harvest efficiencies in organic-Si heterojunction solar cells due to its low light reflection ratio compared with planar one. However, the associated large surface/volume ratio of nanostructured Si suffers from serious surface recombination as well as poor adhesion with organics in organic-Si heterojunction solar cells, which leads to an inferior open-circuit voltage (V-oc). Here, we develop a simple and effective method to suppress charge recombination as well as enhancing adhesion force between nanostructured Si and organics by incorporating a silane chemical, namely 3-glycidoxypropyltrimethoxydsilane (GOPS). GOPS can chemically graft onto nanostructured Si and improve the aqueous organic wetting properties, suppressing surface charge recombination velocity dramatically. In addition, this chemically grafted layer can enhance adhesion force between organics and Si. In such a way, a record V-oc of 640 mV associated with a power conversion efficiency of 14.1% is obtained for organic-nanostructured Si heterojunction devices. These findings suggest a promising approach to low-cost and simple fabrication for high-performance organic-Si solar cells.