Characterizing Morphology in Bulk Heterojunction Organic Photovoltaic Systems

Organic semiconductors are an alternative to inorganic materials in solar cell applications. While the efficiencies of organic photovoltaics (OPVs) have been improving rapidly, they are currently below that required for widespread power generation. OPV performance is sensitive to the nanoscale texture, or film Morphology, in the photovoltaic active layer, particularly in bulk heterojunction, (BHJ) devices, and characterizing morphology across many length scales is currently a major experimental challenge. Here, we discuss several different experimental approaches for characterizing morphology in BHJ systems. These include techniques ranging from X-ray diffraction and spectroscopy to electron microscopy and scanning probe microscopy. These methods provide complementary information to guide future materials design and device optimization efforts.