Rare-Metal-Free Flexible Counter Electrodes for Dye-Sensitized Solar-Cells Produced Using Wet Processes Only

Dye-sensitized solar-cells (DSCs) are cheap because they are produced using low-cost materials and simple manufacturing processes. However, the substrates of DSC counter electrodes are sputtered with a transparent conductive oxide and platinum. This involves vacuum manufacturing processes and high-cost (rare-metal) materials, and increases the costs of DSCs. In this study, we used non-rare-metal low-cost materials and simple wet processes, using combined poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and Ag network (Ag NW) substrates. To solve the problem of Ag NW corrosion by the iodine electrolyte, we hot-pressed the Ag NW substrate and covered with a PEDOT/PSS layer as a barrier against iodine. The PEDOT/PSS layer acted as a catalyst and cells using an Ag NW covered with PEDOT/PSS generated electricity with illumination from both sides. The cell performance was improved by using a PEDOT/PSS layer containing 20 wt % TiO2 nanoparticles (NPs). The performance of the DSSC cell with an Ag NW substrate covered with a PEDOT/PSS layer containing TiO2 NPs (5.13%) was higher than that of a cell using an indium tin oxide substrate covered with the same layer (4.91%). These values are very similar to those of cells using a platinum counter electrode (5.36%). This research showed the possibility of replacing conventional high-cost counter electrodes with low-cost materials, and using only simple wet processes.