Defect Identification in Organic Photovoltaic Devices Using Thermoreflectance Imaging

Organic photovoltaics (OPVs) have many potential advantages over inorganic photovoltaic devices, including physical flexibility and ease of mass production. However, the widespread adoption of OPVs is limited by lower operating efficiencies and susceptibility to degradation in ambient conditions. In this project, we use thermoreflectance imaging, a high-resolution non-contact thermography technique, to locate and explore the physical origins of defects in OPVs. Thermoreflectance images of both commercially purchased InfinityPV solar cells and in-house fabricated, P3HT: PCBM-based organic solar cells show strong, localized regions of enhanced reflectivity, indicative of defects. We identify electrical shunts with radial heat spreading associated with the metal contacts, whereas other defects present as concentric rings with no heat spreading, suggesting a potential mechanical origin. This work illustrates the utility of thermoreflectance imaging as a tool for identifying and characterizing localized defects in organic solar cells.