Effects of Hole-Collecting Buffer Layers and Electrodes on the Performance of Flexible Plastic Organic Photovoltaics

Abstract

Here we report the influences of the sheet resistance (Rsheet) of a hole-collecting electrode (indium tin oxide, ITO) and the conductivity of a hole-collecting buffer layer (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS) on the device performance of flexible plastic organic photovoltaic (OPV) devices. The series resistance (RS) of OPV devices steeply increases with increasing Rsheet of the ITO electrode, which leads to a significant decrease of short-circuit current density (JSC) and fill factor (FF) and power conversion efficiency, while the open-circuit voltage (VOC) was almost constant. By applying high-conductivity PEDOT:PSS, the efficiency of OPV devices with high Rsheet values of 160 Ω/□ and 510 Ω/□ is greatly improved, by a factor of 3.5 and 6.5, respectively. These results indicate that the conductivities of ITO and PEDOT:PSS will become more important to consider for manufacturing large-area flexible plastic OPV modules.