Mohd Fairus Ahmad
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Preferred name
Mohd Fairus Ahmad
Official Name
Mohd Fairus , Ahmad
Alternative Name
Shahimin, Mohd Faidz Mohamad
Mohamad Shahimin, M. F.
Main Affiliation
Scopus Author ID
57006554500
Researcher ID
B-9547-2018

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First-principles investigation on the impact of copper concentration on zinc telluride as the back contact for cadmium telluride solar cells

2024-02-01 , Ahmad N.I. , Doroody C. , Mohd Natashah Norizan , Mohd Fairus Ahmad , Rahman K.S. , Radzwan A. , ALOthman Z.A. , Katubi K.M. , Alzahrani F.M. , Amin N. , Kar Y.B.

Cadmium telluride (CdTe) solar cells have attracted a lot of interest in recent years, attributed to their low cost and eco-friendly fabrication technique. However, the back contact is still the key issue for further improvement in device performance due to the work function difference between p-CdTe and metal contacts. In this study, the interatomic characteristics of zinc telluride (ZnTe) and Cu-doped ZnTe (ZnTe:Cu) as a back surface field (BSF) in CdTe structure is investigated using first-principles density functional theory (DFT) to overcome the Schottky barrier in CdTe solar cells. The incorporation of different doping levels of copper (Cu) in ZnTe on an atomic scale, where Zn1−xTe:Cux (x = 0, 2, 4, 6, 8, and 10) as the potential back surface field layers is investigated. The effect of doping concentration on electrical characteristics such as bandgap structure and density of states (DOS) were examined via ab initio with the Hubbard U (DFT + U) correction. The results showed an interesting gradual decrease in the bandgap energy of ZnTe from 2.24 eV to 2.10 eV, 1.98 eV, 1.92 eV, 1.88 eV, and 1.87 eV for the incremented value of Cu content of 3.13%, 6.25%, 9.38%, 12.50%, and 15.63%, respectively. Accordingly, it has been found that controlling of the effective copper doping, i.e., concentration, is crucial for developing efficient back contact junctions for high-efficiency CdTe thin-film solar cells.

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Copper doping effect in the back surface field layer of CdTe thin film solar cells

2024-02-01 , Nur Irwany Ahmad , Kiong T.S. , Doroody C. , Rahman K.S. , Kar Y.B. , Mohd Natashah Norizan , Mohd Fairus Ahmad , Harif M.N. , Amin N.

In this work, the Solar Cell Capacitance Simulator (SCAPS-1D) is employed to evaluate the characteristics of CdTe thin films with ZnTe as the Back Surface Field (BSF) layer and estimate the effective copper doping ratio at both the atomic scale and the device operational response perspective. The electrical characteristics of ZnTe, at varying levels of copper doping, were derived using density functional theory (DFT) by applying the generalized gradient approximation (GGA) and Hubbard U corrections (DFT+U). The performance of ZnTe with different Cu concentrations as a BSF layer was evaluated by analysing the values of four key parameters that are open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and conversion efficiency (η). The results indicate that an increase in Cu concentration from 0% to 3%, 6%, 10%, and 12% resulted in a reduction of the energy band gap. Specifically, the energy band gap decreased from 2.24 eV to 2.10 eV, 1.98 eV, 1.92 eV, and 1.88 eV, respectively. Optimal Cu doping promotes the favourable shift in the valence band maxima (VBM) and formation of p + -ZnTe, lowering thermionic emission and improving carrier lifetime, which results in an improved ohmic contact, η = 18.73% for 10% of Cu content. Excessive doping in contrast degraded the overall device performance by forming an unmatched carrier band offset at the front interface with CdS, increasing the acceptor type defect and CdTe compensation rate. Overall, the findings suggest that incorporating a controlled level of Cu, which in this case is around 10%, promotes the efficiency and stability of the proposed CdTe device configuration to a certain extent.

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