Investigating morphology and electronic properties of self-assembled hybrid systems for solar cells

We investigate self-assembled network morphologies of hybrid materials and their application in solar cells. We show the use of a semiconducting functional block copolymer as a structure directing agent. The application of a functional block copolymer circumvents an additional filling step of the templated inorganic part with a hole conductor. Within a one-pot synthesis various morphologies adequate for active materials in photovoltaic devices are prepared. The solar cell performance was found to depend on the morphological design of the hybrid material since the formation of percolating networks is of general importance. Using conductive scanning force microscopy on a cross-section of a functional solar cell device, we proved that the titania in our system forms a percolating network. Measurements showed that percolation is not a limiting factor for the device performance. In combination with a functionalized titania-precursor, we were able to double the power conversion efficiency of our hybrid bulk heterojunction cells in comparison to our previous results.