Effect of the nature of cationic precursors for SILAR deposition on the performance of CdS and PbS/CdS quantum dot-sensitized solar cells

In this work, the influences of cationic precursors on the quality of photoelectrode, consequently on the performance of the quantum dot-sensitized solar cells (QDSCs) have been studied. CdS QDSCs have been prepared using successive ionic layer absorption and reaction (SILAR) method. Three cadmium precursors including nitrate (Cd(NO₃)₂), chloride (CdCl₂), and acetate (Cd(Ac)₂) were employed for the synthesis and absorption of CdS nanoparticles on nanostructure TiO₂ film. The loading amount and nanoparticle size of the CdS on mesoporous TiO₂ film showed a significant difference while using various cadmium precursors in the same SILAR cycles. Both the light-harvesting ability and the obtained incident photon-to-current conversion efficiency values show the trend of deposition rate caused by cadmium precursors. Further, it was proposed that an effective cationic precursor could provide a good connection between QD sensitizer and TiO₂ interface by electrochemical impedance spectroscopy analysis. Under AM 1.5 G full one sun illumination, the final power conversion efficiency of CdS QDSC based on Cd(Ac)₂ was 2.10 %, and PCE values of 1.57 and 1.20 % were obtained for solar cells sensitized by CdS QDs prepared by CdCl₂ and Cd(NO₃)₂, respectively. The cationic precursor effect was further applied in PbS/CdS co-sensitized solar cells. The PbS/CdS QDSCs based on acetate cationic precursors provide a photocurrent of 19.24 mA/cm² and PCE of 3.23 % in comparison with 11.26 mA and 2.13 % obtained with nitrate acetate salts. Noticeably, the CdS and PbS/CdS QDSCs based on various cationic precursors prepared by SILAR exhibited good photocurrent stability under several light on–off cycles.