Morphological, Photoluminescence, and Electrical Measurements of Rare-Earth Metal-Doped Cadmium Sulfide Thin Films.

ABSTRACT

This work is aimed at investigating the viability of utilizing cadmium sulfide (CdS) as a buffer layer in CdTe solar cells by analyzing and assessing its optical, photoluminescence, morphological, and electrical properties. These films were fabricated using a thermal coating technique. Optical microscopy was used to observe the changes in morphology resulting from the doping of rare-earth metals such as samarium (Sm) and lanthanum (La) to CdS, while the granular-like structure of the sample was confirmed by scanning electron microscopy. The objective of incorporating Sm and La ions into CdS was to enhance photoconductivity and optimize the optical bandgap, aiming to create a viable charge transport material for photovoltaic devices with enhanced efficiency. Through that process, a noticeable decrease in transmission, from approximately 80 to 68% in the visible region, was observed. Additionally, the bandgap value was reduced from 2.43 to 2.27 eV. Furthermore, during the analysis of the photoluminescence spectra, it was observed that emission peaks occurred in the visible region. These emissions were attributed to electronic transitions that took place via band-to-band and band-to-impurity interactions. The electrical measurements showed an enhancement in conductivity due to the decrease in the bandgap. This notable consequence of the doped materials suggests their utilization in photovoltaic systems.