ZnO/TiO2 nanocomposite photoanode as an effective UV-vis responsive dye sensitized solar cell

Abstract

A facile and simple sol-gel process has been used for the synthesis of TiO2 and ZnO nanomaterials. The varied amount of ZnO is incorporated onto surface of TiO2 by wet chemical impregnation method to fabricate ZnO/TiO2 hetero structures. These hetero systems are employed as photoanodes for dye sensitized solar cell in paste form. The loading of ZnO onto TiO2 surface suppressed the diffraction peaks of anatase phase of TiO2. The particle size is decreased in the composite structure. SEM images showed the spherical agglomerated structure in all samples. The band gap energy values have been reduced in case of ZnO/TiO2 heterojunctions up to concentration of 15.0% ZnO/TiO2. Zn–O–Ti bridging was responsible for low band gap and reduced in the recombination of electron hole. Fourier transforms infra-red spectroscopy confirms the Zn–O–Ti linkage. The depth profile of thin films was determined by Rutherford backscattering spectroscopy. The photoanodes of DSSC fabricated with ZnO/TiO2 nanocomposites were characterized by photocurrent-voltage measurements and exhibited the enhancement in photovoltaic properties as compared to bare TiO2. 15.0% ZnO/TiO2 heterojunction is optimum quantity which delivered 2.8% greater photovoltaic efficiency than bare TiO2 based DSSC. The enhancement is attributed to superior dye loading and reduction in recombination of charge carriers leading to long life time of free electrons that are beneficial for the overall efficiency of device.