A hybrid organic solar cell was fabricated by integrating a layer-by-layer (LbL) ultrathin polymer film with a polymer/fullerene bulk heterojunction film. The short-circuit current density (J(SC)) was significantly improved by a factor of five compared to that observed for LbL-based solar cells. The open-circuit voltage (V(OC)) remained at >0.7V, which is higher than that reported for bulk heterojunction solar cells. These findings suggest that the LbL thin film can not only enhance J(SC) but also tune V(OC). An optimized hybrid polymer solar cell showed the power conversion efficiency to be as high as similar to 1%. (C) 2008 Elsevier B.V. All rights reserved.