Energy-Filtered Backscattered Imaging Using Low-Voltage Scanning Electron Microscopy: Characterizing Blends of ZnPc-C60 for Organic Solar Cells

Energy-filtered backscattered electron imaging in a scanning electron microscope is performed on a blend of zinc-phthalocyanine (ZnPc) and fullerene (C60), whose morphology is characterized using a novel energy selective backscattered (EsB) electron detector in combination with low acceleration voltages for the primary electrons. Such blends are used as an active layer of organic solar cells in bulk heterojunction architectures. The key to optimizing the solar cell performance is understanding the morphology of the blend components. Comparing the results to TEM micrographs, the EsB detector allows for a simple and fast identification of the phases in the blend. The relevance of the findings for applying ZnPc-C60 blends in solar cells is also discussed.