Mapping Nanoscale Variations in the Photoresponse of an Organic Solar Cell

CNST Researchers have combined scanning probe microscopy with novel nanofabrication and microtomy approaches to measure photocurrent variations with nanoscale spatial resolution in an organic solar cell. The most promising architecture for an organic solar cell consists of a blend of conducting materials that can be self-organized from solution into a film that forms the active device layer. The resulting photogeneration efficiency and the charge transport within this film depend strongly on its nanoscale morphology.  

As described in the May 2010 issue of Nano Letters*, the researchers used photoconductive atomic force microscopy (PCAFM), in which a conductive tip is raster-scanned over the film while illuminated, to collect photogenerated charges as a function of position while simultaneously measuring the topography of the film surface. By properly engineering the device structure, fabricating nanoscale contacts, and choosing a specific tip material, the CNST researchers thereby revealed the charge transport via electron or hole conducting regions in the active layer as a function of the film's nanoscale morphology. Understanding how such film morphology affects device performance is crucial to designing new materials for high-performance, next-generation solar cells.

*The Origin of Nanoscale Variations in Photoresponse of an Organic Solar Cell, B. H. Hamadani, S. Jung, P. Haney, L. Richter, and N. B. Zhitenev, Nano Letters 10, 1611-1617 (2010).