Alloying cadmium cobalt sulfide quantum dots for solar cells applications

Abstract

In this work, controlling the optical band gap of alloyed cadmium cobalt sulfide quantum dots (QDs) for solar cells applications is studied. Different cobalt molar ratios (x: 0, 0.1, 0.2, 0.3 and 0.4) of ternary alloyed Cd1-xCoxS QDs have been synthesized onto TiO2 nanoparticles (Titania NPs) electrodes using successive ionic layer adsorption and reaction (SILAR) technique. Transition electron microscope (TEM) has been utilized to characterize the morphological properties of the prepared photoanodes. The structural properties are studied using an X-ray diffractometer. The optical properties of the prepared photoanodes have been measured using a UV–visible spectrophotometer. The energy band gap of the prepared alloyed Cd1-xCoxS photoanodes is systematically red-shifted as the cobalt molar ratio increases. This novel result is discussed in terms of the effective incorporation of cobalt material and Moss-Burstein effect. To the best of our knowledge, the optical bowing parameter (b) of the ternary alloyed Cd1-xCoxS QDs has been determined and equals 0.96 ± 0.14 eV using the modified Vegard's approach for the first time. The prepared alloyed Cd1-xCoxS photoanodes are used for photovoltaic applications. Alloyed Cd0.9Co0.1S QDs sensitized solar cells (QDSSCs) show better photovoltaic performance than bare CdS QDSSC and other rest alloyed Cd1-xCoxS QDSSCs. This result is mainly attributed to the enhancement in the absorption of the solar spectrum and to the good harmonizing of the energetic alignment levels of the QDSSCs’ components. The reproducibility and sensitivity of the assembled QDSSCs undercutting on-off solar illumination are also studied.