Three-dimensional electrodes for dye-sensitized solar cells: synthesis of indium–tin-oxide nanowire arraysand ITO/TiO2 core–shell nanowire arrays by electrophoretic deposition

Abstract

Dye-sensitized solar cells (DSSCs) show promise as a cheaper alternative to silicon-basedphotovoltaics for specialized applications, provided conversion efficiency can be maximizedand production costs minimized. This study demonstrates that arrays of nanowires can beformed by wet-chemical methods for use as three-dimensional (3D) electrodes inDSSCs, thereby improving photoelectric conversion efficiency. Two approaches wereemployed to create the arrays of ITO (indium–tin-oxide) nanowires or arrays ofITO/TiO2 core–shell nanowires; both methods were based on electrophoreticdeposition (EPD) within a polycarbonate template. The 3D electrodesfor solar cells were constructed by using a doctor-blade for coatingTiO2 layers ontothe ITO or ITO/TiO2 nanowire arrays. A photoelectric conversion efficiency as high as 4.3% was achieved inthe DSSCs made from ITO nanowires; this performance was better than that ofITO/TiO2 core–shell nanowiresor pristine TiO2 films. Cyclic voltammetry confirmed that the reaction current was significantly enhancedwhen a 3D ITO-nanowire electrode was used. Better separation of charge carriers andimproved charge transport, due to the enlarged interfacial area, are thought to bethe major advantages of using 3D nanowire electrodes for the optimization ofDSSCs.