Electro-Plating and Characterisation of CdTe Thin Films Using CdCl2 as the Cadmium Source

Nor Abdul-Manaf,Hussein Salim,Mohammad Madugu,Imyhamy Dharmadasa,Olajide Olusola

doi:10.3390/en81010883

Abstract

Cadmium telluride (CdTe) thin films have been successfully prepared from an aqueous electrolyte bath containing cadmium chloride (CdCl2)·H2O and tellurium dioxide (TeO2) using an electrodeposition technique. The structural, electrical, morphological and optical properties of these thin films have been characterised using X-ray diffraction (XRD), Raman spectroscopy, optical profilometry, DC current-voltage (I-V) measurements, photoelectrochemical (PEC) cell measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Vis spectrophotometry. It is observed that the best cathodic potential is 698 mV with respect to standard calomel electrode (SCE) in a three electrode system. Structural analysis using XRD shows polycrystalline crystal structure in the as-deposited CdTe thin films and the peaks intensity increase after CdCl2 treatment. PEC cell measurements show the possibility of growing p-, i- and n-type CdTe layers by varying the growth potential during electrodeposition. The electrical resistivity of the as-deposited layers are in the order of 104 Ω·cm. SEM and AFM show that the CdCl2 treated samples are more roughness and have larger grain size when compared to CdTe grown by CdSO4 precursor. Results obtained from the optical absorption reveal that the bandgap of as-deposited CdTe (1.48–1.52) eV reduce to (1.45–1.49) eV after CdCl2 treatment. Full characterisation of this material is providing new information on crucial CdCl2 treatment of CdTe thin films due to its built-in CdCl2 treatment during the material growth. The work is progressing to fabricate solar cells with this material and compare with CdTe thin films grown by conventional sulphate precursors.

Highlights

Cadmium telluride (CdTe) is one of the most promising photovoltaic (PV) thin film materials for solar cell applications with the conversion efficiency of 21.5%, reported by First Solar in February 2015 [1]
This paper presents the summary of a comprehensive study on cathodic electrodeposition of CdTe thin films grown by 3-electrode system using CdCl2 as the Cd source
These results show complete contrast to the CdTe grown by CdSO4 [19] and Cd(NO3)2 [12] recursors in Figure 8b,c, respectively

Summary

Introduction

CdTe is one of the most promising photovoltaic (PV) thin film materials for solar cell applications with the conversion efficiency of 21.5%, reported by First Solar in February 2015 [1]. Various techniques have been reported for preparation of CdTe thin films such as physical vapour deposition (PVD) [2], RF sputtering [3], spray pyrolysis [4], close-space sublimation (CSS) [5,6] and electrodeposition (ED) [7,8,9,10,11,12]. Electrodeposition is an attractive technique for the preparation of CdTe because of its low-cost, simplicity, scalability, manufacturability and ability to obtain p-, i- or n-type materials by controlling the cathodic voltage during electrodeposition [12,13,14]. Cathodic electrodeposition of CdTe using an aqueous solution of CdSO4 and TeO2 was first reported by Mathers and Turner in [7]. The electrodeposition technique has been widely used and later modified to anodic [15] and non-aqueous deposition [16,17]

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Results

Conclusion