The effect of annealing temperature on structural and optical properties of undoped and Cu doped CdS thin films
Introduction
CdS films are often grown by the chemical bath deposition (CBD) technique, and have shown good properties for device fabrication. The chemical bath deposition of CdS films on glass substrates from aqueous solution is a low-cost process and it is well suited for the manufacture of film solar cells. CdS-CBD films are commonly used as a window or buffer layer material for solar cells of the type CdS/CdTe and CdS/CIGS [1], [2], [3], [4]. Also, there have been studies on Cu doped CdS to obtain p-type Cu:CdS. Generally, they have obtained p-type of these samples by diffusion of Cu. They have achieved an efficiency of 6–7% by a Cu: CdS/CdS homostructure for photovoltaic applications [5], [6]. The efficiency of solar cells is found to be improved with an increase in the conductivity of the Cu:CdS films.
The deposition of CdS films has been explored by different techniques such as thermal evaporation [7], [8], molecular beam epitaxy [9] and spray pyrolysis [10], anodic oxidation [11], cathodic reduction [12] and chemical bath deposition [13]. Development of the chemical bath deposition is widely used because it is a simple and economic and viable technique, which produces films of good quality for device application. This technique has already used for preparation of various semiconducting compound and alloy thin films.
In the present work, an attempt is made to prepare CdS and Cu:CdS thin films by simple and low cost chemical bath deposition technique. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis and optical properties and the results are discussed.
Section snippets
Experimental technique
The undoped CdS and Cu doped CdS thin films were obtained by the method of chemical bath deposition technique. Chemicals used for the deposition of CdS and Cu:CdS were analytical grade cadmium chloride, thiourea, and copper chloride, ammonium hydroxide, and de-ionized water.
The deposition of CdS thin films was performed on glass substrates, immersed in the composition of 0.2 M cadmium chloride (CdCl2·2H2O) was dissolved in 50 ml of de-ionized water and stirred for 10 min using magnetic stirrer. NH4
XRD analysis
XRD patterns of the chemical bath deposited thin films prepared on glass substrates with bath composition 0.2 M CdCl2, 0.2 M SC(NH2)2 and 0.0005 M CuCl2 at bath temperature 80 ± 5 °C are shown in Fig. 1(a)–(d). The XRD patterns revealed that the deposited films are found to be cubic crystal structure is highest peak corresponds to the (1 1 1), (2 2 0), and (3 1 1) phase of undoped and Cu doped CdS. The different peaks in the diffractogram were indexed and the corresponding values of interplanar spacing “d”
Conclusions
The CdS and Cu:CdS thin films are potential candidates used in various application like solar cells and hence they were taken for the present work. The CdS and Cu:CdS thin films were deposited glass substrates at bath temperature 80 ± 5 °C after annealed at different temperatures using an chemical bath deposition technique. X-ray diffraction analysis confirmed that the deposition CdS films are polycrystalline in nature with cubic structure and there is chance in the intensity, addition peaks and
Acknowledgements
The authors are grateful thanks to Sophisticated Test and Instrumentation Centre, Cochin, and Alagappa University, Karaikudi, for providing instrument facilities.
References (18)
- et al.
High efficiency CSS CdTe solar cells
Thin Solid Films
(2000) - et al.
High efficiency, magnetron sputtered CdS/CdTe solar cells
Sol. Energy
(2004) Nano-structural investigations on Cd-doping into Cu(In,Ga)Se2 thin films by chemical bath deposition process
Thin Solid Films
(2000)- et al.
Improvement in the efficiency of Cu-doped CdS/non-doped CdS photovoltaic cells fabricated by an all-vacuum process
Sol. Energy Mater. Sol. Cells
(2003) - et al.
X-ray diffraction studies of p-CdS:Cu thin films
Thin Solid Films
(2002) - et al.
Spray-pyrolysed cobalt black as a high temperature selective absorber
Thin Solid Films
(1982) - et al.
Preparation of c-axis oriented ZnO optical waveguiding films on fused silica by pulsed laser reactive ablation
Mater. Lett.
(1995) - et al.
The electrochemical deposition and formation of cadmium sulphide thin film electrodes in aqueous electrolytes
J. Electroanal. Chem.
(1981) - et al.
Electroplated cadmium chalcogenide layers: Characterization and use in photoelectrochemical solar cells
Thin Solid Films
(1982)