Strategies for solar energy power conversion using thin film organic photovoltaic cells

We discuss the fundamental limitations to solar cell efficiencies employing organic thin films. To support our analysis, several strategies for optimizing the power conversion efficiency of small molecular weight organic PV cells are described. Conversion efficiencies as high as 5.7% at 1 sun, AM1.5G simulated illumination are observed employing thin film tandem cells consisting of CuPc and C-60 as the active region materials. The so-called bulk heterojunction and mixed molecular heterojunction cells is described, as well as that of surface plasmons in tandem cell architectures containing metallic nanoparticle layers separating each sub-cell in a multilayer stack. Surface plasmons are shown to increase the efficiency by a significant fraction in these tandem cells, suggesting that this particular approach has the potential for resulting in solar power conversion efficiencies > 10%.