Properties of (Cd, Zn)S films deposited by DC co-sputtering

CdS thin film is commonly used as a buffer layer in most thin film solar cells.  However, the buffer layer with less absorption in the visible region of the solar spectrum as well as that which provides perfect lattice matching with the absorbers is required. The incorporation of Zn in the CdS films can affect the structural and optical properties of the buffer layer. In this work, films of CdS and (Cd,Zn)S films were deposited by DC sputtering utilizing CdS and Zn targets. The concentration of  Zn in the CdS was varied by changing the sputtering power of the Zn target. The influence of Zn concentration on the structural and optical properties of CdS films was investigated using X-ray diffraction (XRD) and Ultraviolet-Visible-Near Infrared (UV-VIS-NIR) spectroscopy, respectively. The XRD patterns confirm the growth preferential orientation of all films along the (002) plane. UV-VIS spectroscopy results indicate absorption edge shifts toward lower wavelength with an increase of Zn concentration in the CdS. The band gap evaluated by the Tauc plot of these films varied from 2.40 eV to 2.50 eV (0 ≤ x ≤ 0.14). The increased bandgap induces the density of localized states on the edge of the bandgap which leads to the increase in the Urbach tail width.&nbsp

Boron Doped ZnO Films Deposited by DC Reactive Sputtering Using Zn:B Target: Influence of the Deposition Temperature on the Structural, Electrical and Optical Properties

ZnO-based transparent and conducting oxides (TCOs) are commonly used as a window layer in thin-film solar cells. However, TCOs with high transparency in the visible and near-infrared parts of the electromagnetic spectrum, plus excellent electrical properties are required in this application. In this study, TCOs based on ZnO:B films deposited by DC reactive sputtering using Zn:B alloy target were investigated. The impact of deposition temperature on the growth and physical properties of the films was examined. Structural, optical and electrical properties of these films were investigated by means of x-ray diffraction (XRD), Ultraviolet-Visible-Near Infrared (UV-VIS-NIR) spectroscopy, and Hall effect measurement, respectively. The XRD analysis revealed that all films are of hexagonal wurtzite structures, with a preferred orientation along the c-axis. The optical spectroscopy results indicated that all the ZnO:B films had optical transparency above 90% in the visible region which then slightly decreased in the near-infrared region. The highest carrier concentration, conductivity, and mobility were obtained at the deposition temperature of 300 °C–due to improvement in crystal growth–while higher temperatures slightly deteriorated the electrical properties, possibly due to a slight decrease in the crystallite size. Keywords: ZnO; Transparent and conducting oxides; ZnO:B, DC reactive sputtering; deposition temperatur