Photoacoustic and photoelectrochemical current spectra of combined CdS/CdSe quantum dots adsorbed on nanostructured TiO2 electrodes, together with photovoltaic characteristics

We describe the performance of quantum dot (QD)-sensitized solar cells based on CdSe QD sensitizer on a preadsorbed layer of CdS QDs (combined CdS/CdSe QDs) together with the basic studies of optical absorption and photoeletrochemical current characteristics. It can be observed from optical absorption measurements using photoacoustic spectroscopy that the CdSe QDs on the nanostructured TiO2 electrodes preadsorbed with CdS QDs grow more rapidly during the initial adsorption process than those without preadsorption. The maximum incident photon-to-current conversion efficiency (IPCE) value of the CdSe QDs on the nanostructured TiO2 electrodes preadsorbed with CdS QDs is higher than that without preadsorption, indicating the possibilities of decreases in recombination centers, interface states, and inverse transfer rate. Short-circuit current (J(sc)) in combined CdS/CdSe QD-sensitized solar cells shows maximum with the increase in CdSe QDs adsorption times between 2 and 24 h. The other parameters, open-circuit voltage (V-oc) and fill factor, is independent of adsorption time. Therefore, the photovoltaic conversion efficiency (eta) of combined CdS/CdSe QD-sensitized solar cell shows a maximum value of 3.5%. (c) 2010 American Institute of Physics. [doi:10.1063/1.3517066]