Molecular and Morphological Influences on the Open Circuit Voltages of Organic Photovoltaic Devices

• Published in: Journal of the American Chemical Society Vol. 131; no. 26; pp. 9281 - 9286
• Main Authors: Perez, M. Dolores, Borek, Carsten, Forrest, Stephen R, Thompson, Mark E
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08.07.2009
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja9007722

We explore the dependence of the dark current of C60-based organic photovoltaic (OPV) cells on molecular composition and the degree of intermolecular interaction of several molecular donor materials. The saturation dark current density, J S, is an important factor in determining the open circuit voltage, V oc. The V oc values of OPVs show a strong inverse correlation with J S. Donor materials that show evidence for aggregation in their thin-film absorption spectra and polycrystallinity in thin film X-ray diffraction result in a high dark current, and thus a low V oc. In contrast, donor materials with structures that hinder intermolecular π-interaction give amorphous thin films and reduced values of J S, relative to donors with strong intermolecular π-interactions, leading to a high V oc. This work provides guidance for the design of materials and device architectures that maximize OPV cell power conversion efficiency.