Abstract
Electrochemical deposition and characterization of nanocrystallite-CdS thin films for thin film solar cell application are reported. The two-electrode system used provides a relatively simple and cost-effective approach for large-scale deposition of semiconductors for solar cell and other optoelectronic device application. Five CdS thin films were deposited for 45 minutes each at different cathodic deposition voltages in order to study their properties. X-ray diffraction study reveals that the as-deposited films contain mixed phases of hexagonal and cubic CdS crystallites with large amounts of internal strain and dislocation density. Postdeposition annealing results in phase transformation which leaves the films with only the hexagonal crystal phase and reduced strain and dislocation density while increasing the crystallite sizes from 21.0–42.0 nm to 31.2–63.0 nm. Photoelectrochemical cell study shows that all the CdS films have n-type electrical conductivity. Optical characterization reveals that all samples show similar transmittance and absorbance responses with the transmittance slightly increasing towards higher growth voltages. All the annealed films show energy bandgap of 2.42 eV. Scanning electron microscopy and energy dispersive X-ray analyses show that grains on the surface of the films tend to get cemented together after annealing with prior CdCl2 treatment while all the films are S-rich.
Highlights
CdS is a wide bandgap II–VI compound semiconductor with a direct bulk bandgap of 2.42 eV [1]
These results show that CdS layers of similar optical quality can be deposited in this range of growth voltage
Electrodeposition of CdS thin films at different cathodic growth voltages and characterisation of the films before and after postdeposition heat treatment have been presented. The electrodeposition of these layers was carried out using two-electrode system for process simplification and cost reduction
Summary
CdS is a wide bandgap II–VI compound semiconductor with a direct bulk bandgap of 2.42 eV [1]. Due to its desirable properties, it finds use in photovoltaic solar cells [2, 3], piezo transducers [4], photoresistors, luminescence devices [5], Schottky diodes and metal-semiconductor field effect transistors (MESFETs) [6], heterojunction diodes [7], insulated gate thin film transistors [8], and gas sensors [9]. It is used in microelectronics, nonlinear optics, catalysis, photoelectrochemistry [10], and in photodetectors [11]. Report on the use of twoelectrode system for the electrodeposition of CdS is very
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