CaCO3 modification of TiO2 electrodes in dye-sensitized solar cells: Enhanced of electron lifetime and efficiency

Abstract

Herein, we investigate the effects of CaCO₃ coating on TiO₂ photoanode electrodes for dye-sensitized solar cells (DSCs). TiO₂ films are coated with varying thicknesses of CaCO₃ using a spin-coating technique, and the resulting photoanodes are characterized for their structural, optical, and electrochemical properties. Field-emission scanning electron microscopy (FESEM) images reveal that the CaCO₃ coating formed uniform nanocube structures, enhancing the surface morphology and scattering properties of the photoanode. X-ray diffraction (XRD) analysis confirms the presence of both anatase-TiO₂ and calcite-CaCO₃ phases, while optical measurements indicate a slight increase in the bandgap of the CaCO₃-coated TiO₂ films. Photovoltaic testing demonstrates that the optimal CaCO₃ thickness (around 570 nm) significantly improved the power conversion efficiency (PCE) of DSSCs, achieving a maximum efficiency of 9.19 %, compared to 7.58 % for pristine TiO₂. Electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) measurements reveal that the CaCO₃ coating reduced charge recombination, enhanced electron injection, and improved charge transport in the devices. Our results indicate that a thin CaCO₃ layer effectively enhances the photovoltaic performance of TiO₂-based DSCs by reducing electron recombination, improving dye adsorption, and enhancing electron injection, while thicker coatings can negatively affect device performance due to increased recombination and electron transport barriers. These findings provide valuable insights into the design of photoanodes for efficient DSCs, emphasizing the importance of optimizing the CaCO₃ coating thickness.