Highly efficient dye-sensitized solar cells by TiCl4 surface modification of ZnO nano-flower thin film

In dye-sensitized solar cells (DSSCs), the semiconductor photo-anode film plays a significant role in enhancing the overall power conversion efficiency. ZnO is considered as the futuristic hope for photoanodes in DSSCs due to manifold properties over TiO 2 . However, the power conversion efficiency of ZnO-based DSSCs is still low due to its poor chemical stability and surface defects. In this work, we reported the synthesis of ZnO nano-flowers as well as its surface modification of with TiCl 4 at different concentration. In DSSCs, the enhancement in power conversion efficiency results suggested that surface modification of ZnO film by TiCl 4 leads to the deposition of TiO 2 which subsequently increases the roughness factor of film as well as scattering layer. This preferential surface modification of ZnO film facilitates the accumulation of large number of photo-injected electrons in the HOMO of the photoanode with rapid transfer of charge carriers to FTO via ZnO layer by lowering the recombination of photo-injected electrons with the redox electrolyte as well as oxidized dye. The intensity-modulated photocurrent spectroscopy (IMVS) and intensity-modulated photovoltage spectroscopy (IMPS) study also indicated that the recombination rate decreased considerably during the electron transportation. The ZnO film surface modified by TiCl 4 achieved a power conversion efficiency of 4.48%, which is two times higher than that of the non-modified ZnO photoanode.