Photovoltaic and impedance spectroscopic investigation of MEH-PPV blended CdS quantum dot sensitized solar cell

Cadmium Sulphide (CdS) quantum dots (QDs) were deposited on nanostructured TiO₂ film using Successive Ionic Layer Adsorption and Reaction (SILAR) method. The quantum dots were blended with a small quantity of MEH-PPV [Poly(2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] conducting polymer powder mixed with polysulphide electrolyte. Nanostructured TiO₂ on FTO glass and Platinum on FTO are used as photoelectrode and Counter electrode respectively. High resolution Transmission Electron Spectroscopy (HRTEM) image revealed that the CdS QDs adsorbed on TiO₂. The optical properties of CdS QD with MEH-PPV on TiO₂ film were studied by UV-Vis absorbance spectroscopy. The photovoltaic characteristics and impedance spectroscopic properties of CdS QDSSC were analyzed under air mass 1.5 illuminations. At the SILAR adsorption time of 5 min (10 cycles), the maximum efficiency obtained for the FTO/TiO₂/CdS QD +MEHPPV/ Pt/FTO configuration was 1.25% with highest short circuit current density and lowest charge transfer resistance. The measured characteristics of capacitance-voltage showed a decreasing behavior from positive to negative capacitance due to injection of electrons from FTO electrode into TiO₂.