This contribution analyses the performance potential of state of the art organic bulk-heterojunction photovoltaic devices and lives a guideline towards higher device efficiencies. The concept relies on the identification and determination of the relevant material parameters (lifetime, mobility, bandgap, trap density....) for the pristine components and for the blended photovoltaic composites. These material parameters are used as the input for a simulation model, which is demonstrated to correctly describe bulk heterojunction solar cells. Results from simulation are compared to experimental device performance. Comparison between experiment and simulation allows to analyse deficiencies of the pristine compounds, the composite as well as the device architecture. Based on these findings, material and device parameters for a highly efficient bulk heterojunction device are presented. (C) 2003 Elsevier B.V. All rights reserved.