Fabrication of CdS/CdSe bilayer thin films by chemical bath deposition and electrodeposition, and their photoelectrochemical properties

In this work, various kinds of CdS and CdS/CdSe thin films were fabricated on ITO conductive glass by chemical bath deposition (CBD) and/or electrodeposition (ED) methods. These films were characterized by XRD, XRF, SEM and optical absorption. Their photoelectrochemical properties were also investigated. First, two kinds of CdS thin films were firstly deposited on ITO conductive glass by CBD or ED. It was found that the two kinds of CdS films showed different compositions and crystal structures. The CdS film prepared by CBD is S-rich and has a cubic zinc blende structure, while the CdS film prepared by ED is Cd-rich and has a hexagonal wurtzite structure. Furthermore, CdSe was deposited on the as-obtained CdS films by a galvanostatical ED method, resulting in CdS/CdSe bilayer thin films. The achieved CdS/CdSe bilayer thin films showed enhanced optical absorption than the CdS monolayer thin film. For the photoelectrochemical properties, the CdS/CdSe bilayer thin film also exhibited enhanced photocurrent density and photoconversion efficiency in comparison with the CdS monolayer thin film. In particular, the CdS/CdSe bilayer thin film in which the CdS layer was obtained by ED, showed a maximum photocurrent density of about 6 mA/cm2 and maximum photoconversion efficiency of 3.41%.