Hybrid solar cells of layer-by-layer thin films with a polymer/fullerene bulk heterojunction

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 >0.7 V, 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 ～1%.