CdS/CdSe Quantum Dot Co-sensitized Solar Cells

摘要

Quantum dot sensitized solar cells (QDSCs) can be regarded as a derivative of dye-sensitized solar cells (DSCs); the latter has attracted world-wide scientific and technological interest since the breakthrough work done by O'Regan and Gratzel in 1991 for low cost solar cells compared to silicon-based solar cells. Narrow-band-gap semiconductor quantum dots (QDs), such as CdS, CdSe, PbS and InAs, as next-generation sensitizers are considered more promising because of their extraordinary optical and electrical properties. The nanocrystalline ZnO is a good photoelectrode for QDSCs because it possesses high electronic mobility and suitable band gaps. In addition, ZnO is easy to form anisotropic structure (such as nanowires, nanorods and nanotubes) presenting unique electronic and optical properties. Recently, many studies have already been reported on a use of ZnO nanocrystalline for the application in QDSCs. However, the performance of ZnO based QDSCs is very poor. It has been recognized that the charge recombination is one of the main issues to deteriorate the FF of a solar cell, through a process known to occur by transferring the electrons in ZnO to the oxidized ions in the electrolyte. The core-shell configuration is expected to suppress the charge recombination by forming an energy barrier to prevent the electrons in the conduction band of the semiconductor from transferring to ions in the electrolyte, leading to increased open circuit voltage and short current density.