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 Cd 1-x Co x S QDs have been synthesized onto TiO 2 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 Cd 1-x Co x S 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 Cd 1-x Co x S QDs has been determined and equals 0.96 ± 0.14 eV using the modified Vegard's approach for the first time. The prepared alloyed Cd 1-x Co x S photoanodes are used for photovoltaic applications. Alloyed Cd 0.9 Co 0.1 S QDs sensitized solar cells (QDSSCs) show better photovoltaic performance than bare CdS QDSSC and other rest alloyed Cd 1-x Co x S 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.