Efficient counter electrode for copper (I)(II)-mediated dye-sensitized solar cells based on polyvinyl alcohol capped platinum nanoclusters

Abstract

BackgroundCopper complex-mediated dye-sensitized solar cells (DSSCs) have been proven to enhance power conversion efficiency (PCE) due to relatively low driving force for dye-regeneration. A good counter electrode (CE) must possess effective internal charge transfer. Besides, simple fabrication, cost-effectiveness and high surface area of CE are favorable for large-scale application. Conducting polymer poly(3,4-ethylenedioxythiophene), PEDOT, is reported to perform better than platinum (Pt)-based CE. Methods: In this report, we study the influence of various kinds of CEs on performance of copper complex mediated DSSCs. “Dip-coating” methods using polyvinylpyrrolidone capped Pt (PVP-Pt) and polyvinyl alcohol capped Pt (PVA-Pt) are introduced and compared to traditional thermalization method (TR-Pt_10). PEDOT CE is prepared via electrochemical polymerization using aqueous EDOT solution. In addition, deposition mechanisms of PVP-Pt and PVA-Pt on conducting transparent oxide glass are also provided. Significant findingsThe “dip-coating” method not only forms better uniformity of Pt nanoparticles on CE surface but also uses less Pt consumption compared to the TR-Pt_10. From the impedance spectroscopy measurement and cyclic voltammetry analysis, PVA-Pt CE reveals the competitive catalytic activity with PEDOT CE and superior electrochemical stability to PEDOT CE. The PCE of PVA-Pt CE-based device is 8.47 %, which is higher than those using PEDOT (8.30 %), TR-Pt_10 (8.12 %) and PVP-Pt (8.32 %). Pt is reported to perform inferiorly to PEDOT as the counter electrode material for copper complex-mediated DSSC. Through systematic investigation, our work is the first report to explicitly prove Pt is still an outstanding catalyst for copper complex redox couple.