Influence of Sn doping on ZnO nanostructures from nanoparticles to spindle shape and their photoelectrochemical properties for dye sensitized solar cells

The tin (Sn) doped zinc oxide (ZnO) nanostructures were synthesized by the simple hydrothermal method and the photovoltaic performances of Sn doped ZnO derived photoanodes were studied. The doping of Sn significantly altered the morphology of ZnO into spindle shape by the arrangement of small ZnO nanoparticles. The crystalline and structural properties deduced the clear decrement in the crystallite sizes from ~143.9nm to ~82.2nm, which might be suggested the doping of Sn-ions into ZnO nanostructures. X-ray photoelectron spectroscopy (XPS) study showed Sn-O and Zn-O bonding in the synthesized spindle shaped Sn-ion doped ZnO nanostructures, which confirmed the Zn substitution by the Sn-ions. Dye sensitized solar cell (DSSC) fabricated with Sn-ZnO photoanode achieved a solar-to-electricity conversion efficiency of ~1.82% with short circuit current (J _SC) of 5.1mA/cm ², open circuit voltage (V _OC) of 0.786V and fill factor (FF) of 0.45, which was higher than that of DSSC with ZnO photoanode. The increased conversion efficiency and the photocurrent density were attributed to the significant Sn-ion doping into ZnO nanostructures and considerable arrangement of ZnO nanoparticles into spindle shaped morphology which might improve the high charge collection and the transfer of electrons at the interfaces of doped ZnO layer and the electrolyte layer.