Production and characterization of Ni containing CoS based counter electrodes for dye sensitized solar cells

CoS has emerged as a promising counter electrode material for dye sentisized solar cells (DSSC) due to its favorable electrochemical and physical properties, such as high corrosion resistance, fast reaction kinetics, high thermal conductivity, and low production cost. However, its insufficient conductivity, limited ion diffusion rate, high series resistance, and, in some cases, lack of stability under environmental conditions negatively affect device performance. For this reason, it is necessary to incorporate different elements into CoS films to improve the performance of the counter electrode. Therefore, it is important to increase the limited studies related to metal incorporation. In this thesis, Ni element was added into CoS in high volumetric proportions to minimize the factors limiting the DSSC applications of CoS counter electrodes. All electrodes were directly deposited onto FTO substrates using the electrochemical deposition method. CoS, NiS and Ni containing CoS films were produced in 2-dimensional nanoleaf structure. By adding high amounts of Ni, the goal of developing CoS-NiS binary sulfur systems as unique DSSC counter electrodes was achieved. XRD patterns, Raman spectra and FESEM images of all films were taken and their structural and surface properties were examined in detail. The potential use of the materials as counter electrodes in DSSCs was investigated by examining the charge transfer kinetics through electrochemical impedance spectroscopy and the corrosion properties through Tafel plots. It was determined that the high charge transfer resistance of the CoS film decreased as the Ni element entered the structure and the lowest value was obtained in the NiS film. Additionally, the corrosion resistance capacity of the CoS film was improved with the addition of 60% and 80% Ni. According to the CoS film, the corrosion current densities of CoSNi-60 and CoSNi-80 films decreased by 43.83% and 63.31%, respectively, while their corrosion rates were reduced by 43.90% and 63.45%, respectively. Considering all analyses, it was concluded that CoSNi 60 and CoSNi-80 nanoflake films, which exhibit better charge transfer kinetics and greater stability in corrosive environments, are more suitable counter electrode materials for DSSC applications.