Study on the Numerical Modeling of CdTe/CdS/SnO2 Based Thin Film Solar Cells Using SCAPS–1D

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ABSTRACT

In response to changes in material or design, a suitable simulator can be used to predict the novel solar cell’s performance. Employing one dimensional Solar Cell Capacitance Simulator (SCAPS-1D) software, this work analyses cadmium telluride (CdTe) solar cell’s fundamental parameters & performance. The solar cell used for this work is comprised of CdTe(p)-CdS(n)-SnO₂(n⁺); where CdTe, SnO_2, and CdS act as absorber layer, window layer and buffer layer respectively. The work primarily focuses on 1) layer thickness optimization for various layers, 2) the impact of the CdS layer’s electron affinity, and 3) the impact of a highly doped (p⁺) thin layer of CdTe acting as the PV device’s back surface field [1]. The band gap and thickness of the layers are kept constant during simulation at their ideal or predetermined levels. The employed CdTe(p), CdS(n) and SnO₂(n⁺) band gaps are 1.5eV, 2.4eV, and 3.6eV, respectively, with corresponding thicknesses of 2.0 µm, 25 nm, and 0.5 µm. The solar cell’s efficiency dropped from 19.24% to 18.63% as the electron affinity of the CdS layer rose from 3.75eV to 4.2 eV. The addition of a 0.1 µm thick p⁺ rear surface layer increased the efficiency of the solar cell to 21.96%. The optimized absorber, buffer and window layer thicknesses are 4 µm, 15 nm and 0.2µm correspondingly. At an electron affinity of 3.75 eV for the CdS layer, the highest output cell efficiency metrics obtained are J_SC=25.141mA/cm², V_OC=1.0538V, FF%=88.16 % and η%=23.36%.

Significance of the Study:

This study provides critical insights into the optimization of CdTe/CdS/SnO₂ thin-film solar cells using SCAPS-1D simulation. By exploring layer thicknesses, CdS electron affinity, and the incorporation of a p+ CdTe back surface field, the research highlights methods to significantly enhance solar cell efficiency. The findings are pivotal for developing cost-effective and high-performance photovoltaic devices, offering a pathway for future advancements in thin-film solar cell technologies.

Summary of the Study:

Using SCAPS-1D, the performance of CdTe/CdS/SnO₂ solar cells was analyzed with a focus on optimizing layer thickness, CdS electron affinity, and the introduction of a p+ CdTe back surface field. Optimal thicknesses of 4 µm (CdTe), 15 nm (CdS), and 0.2 µm (SnO₂) yielded an efficiency of 23.36%, with metrics JSC=25.14 mA/cm², VOC=1.054 V, and FF=88.16%. The study demonstrates that reducing CdS electron affinity and adding a p+ CdTe layer significantly enhance device efficiency and quantum efficiency.