102 Charaterizing Electron Transport through Organic Photovoltaic Molecules Using Scanning Tunneling Microscopy

Wednesday, November 4, 2009: 9:50 AM
Charolais (Camino Real Hotel)
Shreya Bhattacharyya , Department of Chemistry and the Biodesign Institute, Arizona State University, Tempe, AZ
Ashley Kibel , Department of Physics and the Biodesign Institute, Arizona State University, Tempe, AZ
Paul A. Liddell , Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ
Devens Gust , Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ
Stuart Lindsay , Department of Physics and the Biodesign Institute, Arizona State University, Tempe, AZ
Organic photovoltaics possess the potential to be cheaper, more efficient and flexible in design compared to conventional photovolatics. Organic molecules which may be utilized as solar cell materials typically consist of a chromophore to absorb the incident photons. They may be linked with an electron acceptor to prevent the rapid charge recombination. 

The molecule of our interest consists of a porphyrin (chromophore) linked to a fullerene (electron acceptor) and is known as a molecular Dyad.

The charge separation in Dyads is well established. However, the transport of charge carriers from the molecule to electrodes, as needed in photovoltaic devices, is yet to be fully characterized. In our study we have characterized electron transport through the Dyad moiety from adjacent electrodes using the Scanning Tunneling Microscope (STM) break-junction method. The study involved the immobilization of the Dyads onto the surface of Indium Tin Oxide (ITO) to form a monolayer.  Then we measured and characterized electron transport through Dyad molecules in the dark and under laser illumination. We find that the Dyads form a long-lived charge separation state due to the injection of electrons into the ITO upon laser illumination.