5. CdS Deposition and Characterisation

This chapter provides an insight to the electrodeposition of CdS layers from electrolytic bath without precipitation. CdS layers used in thin-film solar cells as window layers and other electronic devices are usually grown by wet chemical methods using CdCl₂ as the cadmium source and either Na₂S₂O₃, NH₄S₂O₃ or NH₂CSNH₂ as sulphur sources. Obviously, one of the sulphur precursors should produce more suitable CdS layers required to yield the highest performing devices. This can only be achieved by comprehensive experimental work on growth and characterisation of CdS layers from the above-mentioned sulphur sources. This chapter presents the results observed on CdS layers grown by electrodepositing using two-electrode configuration and thiourea as the sulphur precursor. X-ray diffraction (XRD), Raman spectroscopy, optical absorption, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and photoelectrochemical (PEC) cell methods have been used to characterise the material properties. In order to test and study the electronic device quality of the layers, ohmic and rectifying contacts were fabricated on the electroplated layers. Schottky barriers formed on the layers were also compared with previously reported work on chemical bath deposited CBD-CdS layers and bulk single crystals of CdS. Comparatively, Schottky diodes fabricated on electroplated CdS layers using two-electrode system and thiourea precursor exhibit excellent electronic properties suitable for electronic devices such as thin-film solar panels and large area display devices.