Investigators

Michael McGehee, Assistant Professor, Department of Material Science & Engineering; David Goldhaber-Gordon, Assistant Professor, Department of Physics, Stanford University

Objective

This activity explores the use of transparent electrodes made of carbon nanotube (CNT) networks in organic photovoltaics (PVs). CNT-based electrodes have several potential advantages over standard transparent electrodes (such as Indium Tin Oxide) including an extraordinarily large electron mobility, increased contact area, and higher flexibility. This group will study the influence of film roughness on charge collection, film adhesion on the polymer layer, and film work function of the polymer-based PVs. Novel high spatial resolution microscopy techniques will be used to determine limiting factors of film conductivity. The experiments will strive to understand basic causes of low-conductivity found in current CNT films. These measurements will guide the fabrication of future CNT films, as well as provide leads on other forms of graphitic carbon nanostructures that enhance or outperform nanotubes. In addition, the development of scanning probe techniques for the transparent electrodes used here may assist in the investigation of other fundamental processes in excitonic solar cells, such as diffusion and recombination in the active layers.

Annual Reports

Publications

• Rowell, M. W., M. A. Topinka, M. D. McGehee, H. J. Prall, G. Dennler, N. S. Sariciftci, L. Hu, and G. Gruner. “Organic solar cells with carbon nanotube network electrodes.” Applied Physics Letters 88 (23), 233506-1-3, (2006).

Presentations

• McGehee, M. D. “Nanostructured Hybrid Organic-Inorganic Photovoltaic Cells,” Materials Research Society Meeting, San Francisco, CA, April 17-21, 2006.
• Topinka, M. A., M. W.Rowell, M. D.McGehee, L. Hu, D. Hecht, and G.Gruner. “Carbon Nanotube Films as Flexible Transparent Conductors for Solar Cells,” American Physical Society March Meeting, Baltimore, MD, March 13-16, 2006.