Photovoltaic and impedance properties of hierarchical TiO2 nanowire based quantum dot sensitized solar cell

Abstract

Growth and characterization of TiO2 nanowire (NW) assemblies on FTO glass using a typical hydrothermal synthesis have been reported. CdS quantum dots (QDs) have been deposited on TiO2 nanowires by successive ion layer adsorption and reaction (SILAR) method. FESEM image exhibits the flower-like hierarchical TiO2 bunch of nanowires. HRTEM image confirms the size of CdS QDs between 5 and 6 nm. XRD and absorption studies revealed proper growth of CdS quantum dots on TiO2 nanowires. At AM 1.5 illumination intensity, the solar cell, with the configuration FTO/TiO2-NW/CdS-QDs/Pt-FTO, displays a short circuit current (J sc) of 1.295 mA and an open circuit voltage (V oc) of 0.38 V. The V oc and J sc showed linear behavior at higher illumination intensities. The peak in power-voltage characteristics at various illuminations showed a shift towards higher V oc values. Capacitance-voltage (C-V), conductance-voltage (G-V), and series resistance-voltage (R s-V) measurements of the cell in the frequency ranging from 5 kHz to 5 MHz showed decreasing trend of capacitance with increase of frequency whereas increase in conductance and decrease in resistance have been noticed with increase of frequency. All the results including the individual behavior of the plots of capacitance, conductance, and series resistance as a function of bias voltage have been discussed.