A low cost mesoporous carbon/SnO 2/TiO 2 nanocomposite counter electrode for dye-sensitized solar cells

Abstract

Highly porous carbon/SnO 2/TiO 2 nanocomposite films that can be used as counter electrodes in dye-sensitized solar cells (DSSCs) are fabricated by coating a homogeneous and viscous carbon paste on F-doped tin oxide conducting glass. The carbon paste is prepared by ball-milling a mixture of carbon, SnO 2 powder and TiO 2 hydrosol in an organic solution. The composite films are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, Brunauer–Emmett–Teller and Form Talysruf Profiler. The results indicate that the photovoltaic performances of the composite DSSCs are influenced by the content of SnO 2. When the content is increased to 30%, SnO 2 not only acts as “framework” to strengthen the mechanical stability of the composite film but also increases the specific surface area and root-mean-square roughness, which improve fill factor and short-circuit current, finally increasing power conversion efficiency from 5.12% to 6.15%. Cyclic voltammetry analysis and electronic impedance spectroscopy of the optimum composite film display higher catalytic activity for I 3 −/I − redox reactions and much lower charge-transfer resistance compared with Pt, respectively. Dye-sensitized solar cells based on this nanocomposite counter electrode achieve efficiency as high as 6.15% which is comparable to that of the cells using sputtering Pt as counter electrode at similar conditions.