Abstract
Abstract Cadmium sulphide (CdS) thin films were deposited by two different processes, chemical bath deposition (CBD), and pulsed DC magnetron sputtering (PDCMS) on fluorine doped-tin oxide coated glass to assess the potential advantages of the pulsed DC magnetron sputtering process. The structural, optical and morphological properties of films obtained by CBD and PDCMS were investigated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, spectroscopic ellipsometry and UV–Vis spectrophotometry. The as-grown films were studied and comparisons were drawn between their morphology, uniformity, crystallinity, and the deposition rate of the process. The highest crystallinity is observed for sputtered CdS thin films. The absorption in the visible wavelength increased for PDCMS CdS thin films, due to the higher density of the films. The band gap measured for the as-grown CBD-CdS is 2.38 eV compared to 2.34 eV for PDCMS-CdS, confirming the higher density of the sputtered thin film. The higher deposition rate for PDCMS is a significant advantage of this technique which has potential use for high rate and low cost manufacturing.
Highlights
Cadmium sulphide (CdS) is an important II–VI compound semiconductor material with applications in several heterojunction photovoltaic systems including cadmium telluride (CdTe), copper indium diselenide/ sulphide and copper indium gallium diselenide/sulphide (CIGS) solar cells [1]
The very intense b 002N reflection for the pulsed DC magnetron sputtering (PDCMS) CdS indicates the hexagonal structure with a preferential orientation b 001N, whereas the chemical bath deposition (CBD) CdS films exhibit a cubic polycrystalline structure
The grains expand through the thickness of the film deposited by PDCMS with a columnar structure (a) while small grainy crystallites grow through the thickness of CBD CdS film (b), consistent with the SEM images and X-ray diffraction analysis (XRD) data
Summary
Cadmium sulphide (CdS) is an important II–VI compound semiconductor material with applications in several heterojunction photovoltaic systems including cadmium telluride (CdTe), copper indium diselenide/ sulphide and copper indium gallium diselenide/sulphide (CIGS) solar cells [1]. It has applications in various electro-optic and infrared devices [2]. The major advantage of the PDCMS process is that it produces high deposition rates which are much higher than those obtained using RF sputtering [19] This makes the use of pulsed DC sputtering suitable for high throughput solar module manufacturing [18]. The use of pulsed DC power supplies avoids the need for complex matching circuits necessary when using radio frequency power supplies
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