The optical and electrochemical properties of CdS/CdSe co-sensitized TiO2 solar cells prepared by successive ionic layer adsorption and reaction processes

Quantum dot sensitized nanocrystalline TiO2 solar cells (QDSSCs) are promising third-generation photovoltaic devices. A series of CdS/CdSe co-sensitized TiO2 photoanodes for QDSSCs were prepared by successive ionic layer adsorption and reaction (SILAR) processes. The growth of CdS and CdSe layers were monitored by taking UV-Visible absorption spectra and the SILAR cycles of CdS and CdSe show different impact on the performance of QDSSCs. With the deposition times of CdS increasing (from 4 to 7 cycles), the short-circuit current density of the device is enhanced. On the contrary, the increasing deposition times of CdSe (from 4 to 7 cycles) has a negative effect for the generation and collection of photoelectron. In addition, the electrochemical impedance spectroscopy technology was used to investigate the impedance of diffusion and recombination in the various devices. Moreover, the effect of SILAR cycles on the recombination resistance was discussed based on the electrochemical impedance spectroscopy results. (C) 2012 Elsevier Ltd. All rights reserved.