Electrochemical properties of TiO_2 encapsulated ZnO nanorod aggregates dye sensitized solar cells

摘要

Dye sensitized solar cells based on TiO_2 encapsulated ZnO nanorod (NR) aggregates were fabricated and electrochemical performance was analyzed using impedance spectroscopy as a function of forward bias voltage. Charge transfer properties such as electron life time (τ_n), electron diffusion coefficient (D_n) and electron diffusion length (L_n) were calculated in order to ensure the influence of TiO_2 layer over the ZnO NR aggregates. It is found that the short circuit current density (Jsc = 5.8 mA cm~(-2)), open circuit potential (V_(oc) = 0.743 V), fill factor (FF = 0.57) and conversion efficiency are significantly improved by the introduction of TiO_2 layer over ZnO photoanode. A power conversion efficiency of about 2.48% has been achieved for TiO_2/Zn0 cell, which is higher than that of bare ZnO NR aggregate based cells (1.73%). The formation of an inherent energy barrier between TiO_2 and ZnO films and the passivation of surface traps on the ZnO film caused by the introduction of TiO_2 layer increase the dye absorption and favor the electron transport which may be responsible for the enhanced performance of TiO_2/ZnO cell.