Effect of TiO2 morphology on photovoltaic performance of dye-sensitized solar cells: nanoparticles, nanofibers, hierarchical spheres and ellipsoid spheres
Different morphologies of anatase TiO2 from nanoparticles, nanofibers, and hierarchical spheres to ellipsoid spheres are successfully fabricated via solvothermal reactions of titanium n-butoxide and acetic acid. The variations of morphology, size and crystal phase of TiO2 micro-/nanostructures are investigated in detail by XRD, FTIR, SEM and TEM. Effects of different TiO2 morphologies on the photovoltaic performance of dye-sensitized solar cells (DSSCs) are also discussed based on I–V, IPCE, IMPS, IMVS and UV-vis absorption and diffuse spectra. The DSSC based on the hierarchical anatase TiO2 sphere photoelectrode shows an overall light-to-electricity conversion efficiency of 9.35% accompanying a short-circuit current density of 17.94 mA cm−2, an open-circuit voltage of 803 mV and fill factor of 0.65, which is much higher than that of nanoparticles (7.37%), nanofibers (8.15%) and ellipsoid TiO2 spheres (7.93%). The significant enhancement of short-circuit current density and power conversion efficiency for the hierarchical sphere-based DSSC compared to other nanostructures is mainly attributed to the larger dye loading, superior light scattering ability, and/or faster electron transport and longer electron lifetime.