Conductive atomic force microscopy (C-AFM) analysis of photoactive layers in inert atmosphere

Conductive atomic force microscopy (C-AFM) measurements have been performed on the MDMO-PPV/PCBM system which is potentially interesting for applications as active layer in polymer solar cells (PSCs). It is demonstrated that C-AFM analysis performed in air for ambient conditions provides only inadequate information about the local electrical properties. The main reason is that the samples chemically degrade when in contact with air. Moreover, we speculate that also the adsorbed water layer interferes with reliable nanoscale electrical measurements. In contrast, when performed in inert atmosphere C-AFM analysis offers consistent results of e.g. the I–V characteristics with lateral resolution better than 50 nm, and is able to detect local heterogeneities of these I–V characteristics at the sample surface.