A Review on CdTe Thin Films Deposited by Different Methods for Solar Cell Applications

International Journal of Research and Scientific Innovation (IJRSI) | Volume VII, Issue IV, April 2020 | ISSN 2321–2705

A Review on CdTe Thin Films Deposited by Different Methods for Solar Cell Applications

Abinaya.S, Vinoth.G, Mohan Rangam Kadiresan
Department of Physics, Karpagam Academy of Higher Education, Eachanari Post, Pollachi Main Road, Coimbatore – 641 021, Tamilnadu, India

Abstract:-Cadmium Telluride(CdTe) plays a significant role in thin film solar cell technology. It is the most favourable thin film material because of its minimum material usage and rising efficiency of nearly 22%. In 2016, CdTe thin film technologies acquired a market share greater than 55%. CdTe solar cell has become the most important among thin film technologies because its high efficiency. Because of the bandgap level and the preparation methods, CdTe becomes one of the leading materials in thin films solar cell applications. This review shows the preparation methods of CdTe and their bandgap levels at different substrates at different annealing temperature and their applications in solar cells.

Keywords: vacuum evaporation, CdTe, solar cell applications.

I. INTRODUCTION

Several materials has been examined for the applications of solar cells[33], which may contribute to the growth of current and interesting types of semiconductor materials like thin film polycrystalline, amorphous silicon, crystalline silicon materials namely cadmium zinc telluride (CZT), zinc telluride (ZnTe) and cadmium telluride(CdTe)[29]. Binary semiconducting compounds (CdS, CdSe, CdTe) belonging to II-VI group of cadmium chalcogenide family have been studied and found to play a vital role because of their effective use in light-conductive devices and solar cells[1,2]. Among these compounds, CdTe has been accepted as the most favourable material due to its high absorption coefficient in the visible region (>105 cmˉ1) and optimal bandgap 1.45 eV[3]. In the last decade, major research has been done on cadmium telluride thin films mainly owing to their large area of utilization in the branch of optoelectronic devices such as lasers, nonlinear integrated optical devices, optical filters, X- ray detectors, radiation detectors, field effect transistors, light-emitting diodes (LEDs), photo detectors and thin film solar cells[4-8].
Cadmium telluride thin films have been fabricated by chemical and physical techniques such as spray pyrolysis, metal organic chemical vapour deposition, close-space sublimation, thermal vacuum evaporation, pulsed laser deposition, electro deposition and magnetron sputtering[9-15]. The chemical and physical thin film properties mainly rely on the substrate temperature, doping, substrate, annealing, film thickness and fabrication techniques[3].
The annealing can be carried out in gaseous medium such as Ar, N2, H2 and air as well as in vacuum[3]. CdTe allows ˃90% of an incident light to absorb by a minimum thickness (µm) because it has a very sharp absorption edge[16,17]. Siyanaki et al. reported that the bandgap, grain size and refractive index of cadmium telluride thin films could be controlled by the rotation rate of the substrate [18].

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