Systematic Study of the Optimization of Cadmium Telluride (CdTe) Thin-film Solar Cell Performance Using Spherical Plasmonic Metal Nanoparticles

Abstract

Cadmium Telluride (CdTe) has gained significant attention as a leading semiconductor absorbing material in thin-film solar cells (TFSCs) due to its high absorption coefficient in the visible to the near-infrared (NIR) region, near-optimum band gap energy, relatively low carbon footprint and production cost. Additionally, CdTe is also a direct band gap material having a direct band gap that has a favorable match with the solar spectrum. Hence, this offers high theoretical efficiencies, which significantly reduces the thickness of the absorbing layer when compared to other materials (e.g., silicon) used in TFSCs. Additionally, Cadmium (Cd) is readily available mainly as a byproduct of the mining industry. Hence, CdTe solar cells now have the lion's share of the TFSC market. However, limited availability of Tellurium (Te) is one of the major challenges hindering the development of CdTe solar cells. Therefore, it is important to design new highly efficient CdTe TFSCs with ultra-thin layers that can significantly reduce the demand on Te. One such method can be coupling plasmonic metal nanoparticles to the absorbing layer of CdTe TFSCs to improve the light absorption and current generation capacity of the solar cells. In this light, this computational study was conducted using the Finite-Difference Time-Domain (FDTD) method that used spherical plasmonic nanoparticles of various metals, e.g., silver, gold, aluminum and titanium, and of different sizes coupled to the absorbing substrate of CdTe TFSCs to investigate their effect on the opto-electronic performance of the solar cells. The results show that the opto-electronic performance of CdTe TFSCs is significantly enhanced by most of the metal nanoparticles mentioned, with silver showing the most significant enhancement. It was observed that 150 nm diameter spherical silver nanoparticles placed on the top surface of CdTe TFSCs, yields greater than 25% enhancement in the short-circuit current density (Jsc) when compared to bare CdTe TFSCs. It was also observed that the other performance parameters of CdTe TFSCs such as open-circuit voltage, fill factor, output power and efficiency also show enhancements with the presence of spherical plasmonic metal nanoparticles. It is hoped that the encouraging results of this study can inspire exciting new research to significantly improve the opto-electronic performance of CdTe TFSCs using different innovative mechanisms.