Dye-sensitized Solar Cells Based on Double-layer Composite Film with Enhanced Photovoltaic Performance

Abstract

Dye-sensitized solar cells (DSSCs) were fabricated using TiO 2 nanorod arrays as underlayer and hybrid nanosheets-microspheres as overlayer, where 1 dimensional TiO 2 nanorod arrays, 2 dimensional TiO 2 nanosheets, and 3 dimensional TiO 2 microspheres were prepared by hydrothermal method. Nanosheets/microspheres hybrid structures with different weight ratios were fabricated in order to study the structural effect of photoanodes on the solar cell performance. The samples were characterized by field emission scanning electron microscope, N 2 adsorption-desorption isotherms, X-ray diffraction, UV-Vis diffuse reflectance spectra, photoluminescence (PL) spectra, and electrochemical impedance spectroscope. The results showed that both optical and electrical properties of photoanodes and photovoltaic performances of DSSCs were obviously influenced by the weight ratios of nanosheets/microspheres. It was found that the electrode made from 50wt% nanosheets had the largest dye-loading, highest light absorption, smallest inherent resistance, and lowest PL intensity, comparing with those made from other weight ratios of nanosheets. The performances of DSSCs made from 25wt%, 50wt%, 75wt%, and 100wt% nanosheets double-layered electrodes were studied in detail, with corresponding efficiencies of 1.46%, 1.71%, 1.26%, and 1.13%. This can be ascribed to that the cell made from 50wt% nanosheets has strong light absorption, reduced carrier recombination rate, and enhanced electrons transport.