Improved performance of CdS quantum dot sensitized solar cell by solvent modified SILAR approach

CdS quantum dot sensitized solar cells were fabricated using a solvent modified successive ionic layer adsorption and reaction (SILAR) method. The power conversion efficiency (PCE) of the device (TiO2/CdS/ZnS) fabricated by the modified SILAR was increased from 2.8% to a maximum of 3.70%. This was achieved by the use of ethanol in the cadmium precursor solution and methanol in the washing step, instead of the ethanol or methanol solutions used in both steps in the conventional SILAR method. The ethanol - methanol SILAR method enhanced the photovoltaic parameters of the QDSSC by increasing the light absorption and reducing the recombination rate of electrons in the device determined by UV-Vis absorbance spectroscopy and electrochemical impedance spectroscopy. These effects were mainly attributed at the better wettability of ethanol with the TiO2 surface against the use of methanol or water and the higher solubility of Na2S in methanol instead of ethanol in the washing step, resulting in more homogeneous distribution of S−2 ions to react with the already adsorbed Cd2+ cations.