Scanning probe microscopy is increasingly being utilized to study the properties of organic photovoltaic materials at both the nanoscale and the single molecule level. The Atomic Force Microscope (AFM) has the ability to study both the morphological properties of organic film devices, as well as electronic properties such as conductance and surface potential. The scanning tunneling microscope (STM), similarly, can study the electronic properties of single photovoltaic molecules.
We have studied the conductance properties of photovoltaic substrates and organic thin films of light absorbing molecules using current sensing atomic force microscopy (CS-AFM). We have also directly observed the conductance properties of single porphyrin-fullerene dyad molecules on Indium Tin Oxide electrodes using STM by observing tunnel junction conductance switching caused by single molecule binding events in the time domain. We find that the scanning probe microscope is a useful tool in the electrical characterization of organic photovoltaics and has the potential to help influence organic photovoltaic design and improvement.