The Role of C60 Barrier Layer in Improving the Performances of Efficient Polymer-Based Photovoltaic Devices: An AFM/EDXR Time-Resolved Study

Abstract

Here, we report an in situ study of the effect of morphological/structural aging processes on polymer-based photovoltaic cell performances. The devices were provided with a fullerene film as a barrier layer between the active element and the metallic cathode. The experimental method adopted consists of the joint use of atomic force microscopy (AFM) and energy dispersive X-ray reflectivity (EDXR), an original coupling particularly effective in the study of stratified media. These techniques were applied first to the intermediate stages of the device construction and, finally, to a complete cell. The problems related with the surface/interface modifications of the devices elements in operating conditions were investigated in depth, with particular concern on the role of the C60 barrier layer. The C60 film surface topography was monitored by AFM experiments during illumination, which evidenced a surface reorganization of the C60 layer molecules over time. Conversely, the C60 film bulk and its interface with ...