Influence of Indium Tin Oxide Surface Treatment on Spatially Localized Photocurrent Variations in Bulk Heterojunction Organic Photovoltaic Devices
A correlation between anode surface treatment and spatially localized photocurrent variations has been found in bulk heterojunction poly(3-hexylthiophene):[6,6]-phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) organic photovoltaic (OPV) devices. Atomic force photovoltaic microscopy was used to scan arrays of 2 μm diameter OPV devices with varied indium tin oxide (ITO) surface treatments. The standard deviation of the average photocurrent was found to be 11.4% for devices fabricated on untreated ITO, 8.6% for devices with a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) interlayer, and 6.7% for devices with a HCl-treated ITO surface. These results suggest that spatial variations in the structure and electronic properties of the anode surface degrade the overall performance of OPVs, including reductions in short-circuit current by up to 20%, thus highlighting the importance of surface treatments that improve the homogeneity of ITO.