Defect Characterization of Organic Photovoltaics

Polymer based organic photovoltaic devices (OPVs) have attracted a great deal of interest because of their mechanical flexibility, tunable material properties, and potentially low cost, with demonstrated efficiencies of up to 10.6% [1]. However, non-uniformities and defects can decrease the operating efficiency, and exposure to oxygen and moisture under working conditions can progressively degrade the cells over time. In this work, we demonstrate the use of highly spatially resolved thermoreflectance imaging to examine electrical shunts and other defects in P3HT-based devices. Examining the thermal signature of a defect in response to sweeping the cell bias conditions, together with more conventional means of characterization including IV curves and electroluminescence imaging, provides a powerful tool for characterizing the types and physical origin of defects present in the cells.

[1] Gang Li, Rui Zhu, and Yang Yang, “Polymer Solar Cells,” Nature Photonics, vol. 6, March 2012, pp.153-161.