We present and experimentally verify a monte-carlo model of energy transport in planar heterojunction organic solar cells showing that an appropriately engineered planar multilayer stack can achieve power conversion efficiencies comparable to the best bulk heterojunction devices. The key to this surprising performance is careful control of the optical properties and thicknesses of each layer to optimize Forster resonance energy transfer from antenna/transport layers to a central reaction center, much as in the first steps of photosynthesis. We refute the orthodox view that a bulk heterojunction is required to achieve high power conversion efficiencies with organic materials, and suggest that planar heterojunction devices with optimized energy transport may be the best path forward for commercialization due to the straightforward modeling, engineering, and fabrication of these structures.