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

Dye-sensitized solar cells (DSSCs) show promise as a cheaper alternative to silicon-based photovoltaics for specialized applications, provided conversion efficiency can be maximized and production costs minimized. This study demonstrates that arrays of nanowires can be formed by wet-chemical methods for use as three-dimensional (3D) electrodes in DSSCs, thereby improving photoelectric conversion efficiency. Two approaches were employed to create the arrays of ITO (indium–tin-oxide) nanowires or arrays of ITO/TiO₂ core–shell nanowires; both methods were based on electrophoretic deposition (EPD) within a polycarbonate template. The 3D electrodes for solar cells were constructed by using a doctor-blade for coating TiO₂ layers onto the ITO or ITO/TiO₂ nanowire arrays. A photoelectric conversion efficiency as high as 4.3% was achieved in the DSSCs made from ITO nanowires; this performance was better than that of ITO/TiO₂ core–shell nanowires or pristine TiO₂ films. Cyclic voltammetry confirmed that the reaction current was significantly enhanced when a 3D ITO-nanowire electrode was used. Better separation of charge carriers and improved charge transport, due to the enlarged interfacial area, are thought to be the major advantages of using 3D nanowire electrodes for the optimization of DSSCs.