FABRICATION AND EFFICIENCY EVALUATION OF DYE-SENSITIZED SOLAR CELL BASED ON VARIOUS ELECTRODE MATERIALS

Abstract

One of the challenges for efficient and low-cost dye-sensitized solar cells (DSSCs) is the development of suitable cost- effective counter electrode (CE) materials. CE must be able to accept and release electrons efficiently. Platinum is generally used as catalytic CE for redox mediators in electrolyte solution. Unfortunately, platinum is expensive and non-sustainable for long-term applications. Therefore, researchers are developing low-cost and earth abundant alternatives. In this study, the composites of polymer (Polyaniline and Polypyrrole) with metals (silver, gold, copper) were synthesized by electrodeposition technique. These composites were tested for potential use as a highly efficient electrocatalyst for CE in DSSCs. Compared to the bare polymer CE, metal/polymer composite (silver/polyaniline, gold/polyaniline, copper/polyaniline, silver/polypyrrole, gold/polypyrrole and copper/polypyrrole) CEs show a high electrocatalytic activity for I3−/I− redox reaction, demonstrated by higher cathodic peak currents, lower values of peak to peak separation, and greater exchange current densities. The large electrocatalytic activity is of great significance for improving the efficiency of DSSCs. Among the different metal/polymer composites, copper/polypyrrole composite based DSSC exhibits a highest power conversion efficiency of 7.42%. This power conversion efficiency is also greater than a thermally decomposed Pt based DSSC (6.18%). The improved efficiency of the DSSC is due to following aspects: Firstly, polypyrrole film shows a porous surface that leads to improve the electrolyte/electrode interaction, employing additional electrocatalytic sites for the reduction of triiodide. Secondly, the high electron-transport network formed by the Cu nanorods on polypyrrole surface is also responsible for enhanced efficiency. This highlighted the importance of the large surface area, good accessibility of electrolyte into the CE, and appropriate conductivity of composite material, underlining a synergetic effect between polymer and metal nanostructures. The main limitation of DSSC is, however, the heavy, expensive, and inflexible transparent conducting glass typically used as CE substrate. To address this problem, this study concentrates on the transfer of the DSSC technology from transparent conducting glass substrates to light- weight, cost-efficient and flexible stainless steel sheet as CE substrate.