Effects of CdCl2 Treatment on Physical Properties of CdTe/CdS Thin Film Solar Cell

Abstract

We report CdTe, CdS, and ITO thin films on glass substrates for solar cell fabrication by closed space sublimation and chemical bath deposition. CdTe and CdS thin films were sublimated to chemical treatment at 25°C in a saturated CdCl 2 solution (1.04 g/100 ml methanol) and heat treated at 400°C for 30 minutes. Indium tin oxide and tellurium films were analyzed by spectrophotometer and scanning electron microscopy. It has been observed that solar cell performance can be improved by depositing a CdCl 2 layer on the CdTe/CdS layers. The optical, structural, and morphological changes of CdTe and CdS surfaces on CdTe/CdS/ITO/glass solar cells due to CdCl 2 solution treatment followed by annealing for 400°C were studied. Optical analysis showed about 15% decrease in transmittance after CdCl 2 heat treatment in case of CdTe thin film, whereas CdS thin film demonstrated an increase of about 10-15% transmittance after CdCl 2 heat treatment. Similarly, a decrease in band gap values was found for both CdTe and CdS thin films after CdCl 2 heat treatment. XRD and SEM results of CdCl 2 heat-treated CdTe and CdS samples showed recrystallization, reorientation, and progressive increase in grain size. The grain sizes of CdTe and CdS samples demonstrated an increase of about 0.2 µm.

A Comparative Study of (Cd,Zn)S Buffer Layers for Cu(In,Ga)Se2 Solar Panels Fabricated by Chemical Bath and Surface Deposition Methods

“…These images also indicate that the buffer layers have a granular structure with very well defined granular boundaries. Generally, the CdS is known to have a very good match with the ITO glass substrate, as reported previously [8,30]. Nonetheless, the SEM images in Figure 2a indicates the buffer layer prepared by the CBD method has larger granules than the film formed by the CSD method (Figure 2b).…”

“…While much effort for the recent laboratory cells has been focused on the development of the buffer layer using various vacuum and in-line deposition processes [4][5][6], the buffer layer formation process for the commercially available large-scale CIGS photovoltaic (PV) panels has still remained at a conventional wet-chemical cadmium sulfide deposition stage [1,7]. Notably, chemical bath deposition (CBD) of CdS is very reproducible and yields good step coverage on any chalcopyrite absorber, including CIGS and CdTe [3,8], which are widely used both in PV and photoelectrochemical applications [9].…”

Ultra-thin CdTe film properties enhancement via eco-friendly MgCl2-assisted thermal treatment

“…For instance, the current technology requires 5 tons of CdCl 2 (cost: approximately USD 1,500,000) to produce a single gigawatt of CdTe solar cells [9] and additional costs are expected to the production for management and dumping, which necessitates a specialized industrial plant to safeguard the waste disposal operators and specialists. Regardless of this, CdCl 2 has been utilized for the thermal treating of CdTe for more than 30 years [10], and a variety of other methods based on CdCl 2 have been developed and employed [11][12][13][14]. However, relatively little effort was put into developing alternative materials for CdTe thermal treatment.…”

The viability of alternative and nontoxic chlorine containing compounds for thermal treatment of ultrathin CdTe (≤1.0 μm) films

“…As an example, a single gigawatt CdTe solar cell production, 5 tons of CdCl 2 (price around 1 500 000 USD) is required in the current technology 18 and more costs further added to the production for handling and disposal, which require a specific industrial plant to protect the waste disposal operators and specialists. Despite that, the usage of CdCl 2 in CdTe solar cell fabrication has endured more than 30 years, 19 and many alternative approaches based on CdCl 2 have been used for the thermal treatment of CdTe including CdCl 2 vapor, 20 CdCl 2 layer deposition, 21,22 and CdCl 2 solution or wet treatment. 23 On the other hand, very little effort was made for achieving alternative materials for CdTe thermal treatment and yet to found imperious.…”