Cascade Structured ZnO/TiO2/CdS quantum dot sensitized solar cell

Cascade structure of ZnO/TiO2/CdS quantum dot sensitized solar cell (QDSSC) using precursor solutions of CdS quantum dots having different concentrations such as 0.1 M, 0.2 M, 0.5 M and 0.8 M were synthesized on fluorine doped tin oxide (FTO) substrate, using the successive ionic layer absorption and reaction (SILAR) method. A polysulfide electrolyte was used as a redox mediator. The combination of ZnO/TiO2 used as a photoanode gives the best results and changes the mechanism of the QDSSC. The conventional Pt counter electrode was replaced by a low cost CuS counter electrode. Morphological and structural characterizations were carried out by field-emission scanning electron microscope (FESEM) & X-ray diffractometer, respectively. The optical characterizations were carried out by using ultraviolet-visible (UV-Vis) spectroscopy. Degree of porosity of prepared quantum dot (QD) sensitizers on TiO2/ZnO surface of different precursor concentrations 48.90%, 45.90%, 44.20% and 42.41% were observed. J-V characteristics and the performance of the prototype solar cell devices were evaluated by using a solar simulator, under illumination with an AM 1.5G spectrum having light intensity of 100 mWcm(-2). The highest efficiency was obtained 2.44% at 0.1 M concentration and the lowest was 0.52% at 0.8 M concentration.