Optimizing anatase TiO₂ through aluminium doping: A comprehensive study for enhanced dye-sensitized solar cell performance

With its consistent porosity, enhanced crystallinity, improved light absorption and superior dye loading, Al-doped TiO₂ exhibits exceptional photoelectrochemical qualities. These variables are essential for dye-sensitized solar cell (DSSC) performance enhancement and photoanode optimization. Despite a great deal of research, the relationship between doping concentration, defect states, and overall device performance is still unknown. Here in this study we have tried to address this research gap by synthesizing Al-doped TiO₂ nanoparticles with varying concentrations (0.1 M, 0.2 M, and 0.3 M) using the sol-gel method and systematically analyzed for their optical, electrochemical, and morphological properties with the intention of finding the optimal dopant concentration and its effect upon the defect states and DSSC performance. Comprehensive characterization revealed that the 0.2 M Al-doped TiO₂ exhibited enhanced crystallinity and dye loading with improved light absorption, owing to its larger surface area and uniform porosity. Electrochemical impedance spectroscopy and Mott-Schottky analysis confirmed that Al doping improved conductivity, charge carrier separation, and reduced recombination rates, particularly at the optimal doping concentration of 0.2 M. In agreement with the experimental results, theoretical calculations employing density functional theory (DFT) demonstrated that Al doping narrowed the bandgap and introduced donor-like states, improving visible-light-driven applications. Photovoltaic performance assessments revealed a peak power conversion efficiency (PCE) of 1.34 % for DSSCs fabricated with the 0.2 M Al-doped TiO₂ photoanode, outperforming pure and other doped samples. This improvement is attributed to reduced charge transfer resistance, increased carrier lifetime, and optimized energy level alignment. These findings demonstrate that 0.2 M Al³ ⁺ doping is an effective strategy for enhancing the efficiency of TiO₂-based DSSCs and offer insights into optimizing dopant concentrations for advanced energy conversion applications.