Solvothermal design of hierarchically interdigitated TiO2 photoanodes with controlled nano-topology for efficient and scalable dye-sensitized solar cells

Abstract

The rational design of photosensitized solar cell (DSSCs) which is sensitive to improving the absorption of light, to transport the charges, and the stability of the structure is a key determinant to the development of the cell. This work describes the solvothermal synthesis of hierarchically interdigitated TiO₂ nanorod photoanodes with customized nanotopology, which are fabricated to maximize the movement of electrons and the ability to collect photons. The interdigitated architecture promotes directional charge transport, minimizes recombination losses, and significantly expands the active surface area for dye adsorption. XRD confirms the formation of nanorods with optimal crystallite size (∼36.7 nm), reduced lattice strain, and favorable oxygen vacancy concentrations. SEM analysis revealed vertically aligned nanorods with uniform dispersion and optimal inter-rod spacing, facilitating efficient electrolyte penetration. TEM characterization further confirmed high aspect ratio (≈10:1), defect-free lattice fringes, and single-crystalline nature of the nanorods. XPS deconvolution indicated the presence of Ti³⁺ species and controlled oxygen vacancies, contributing to improved electronic conductivity and dye anchoring. Upon integration into DSSC devices, the solvothermally derived TiO₂ photoanodes yielded a power conversion efficiency (PCE) of 5.90%, representing a 20.6% enhancement over standard cells. The improvement is attributed to enhanced short-circuit current density (20.37 mA/cm²), minimized series resistance (67.8 Ω), and optimized interfacial charge transfer resistance (147.2 Ω). These findings establish a direct structure–property–performance relationship, demonstrating that morphology-guided, defect-engineered TiO₂ architectures enable synergistic improvements in both photophysical and electrochemical behavior, providing a scalable platform for developing next-generation DSSCs with superior performance and stability.