Band edge movement in dye sensitized Sm-doped TiO2 solar cells: a study by variable temperature spectroelectrochemistry

Abstract

Pure TiO₂ and 8 at% Sm-doped TiO₂ nanoparticles are prepared via a novel hydrolysis followed by a hydrothermal process at 473 K for 24 h and successfully used in the photoanode of dye sensitized solar cells (DSSCs). The performance of DSSCs based on 8 at% Sm-doped TiO₂ is significantly better compared to DSSCs based on undoped TiO₂. The J_sc is 14.53 mA cm⁻² and η is 6.78%, which is 15% and 5% higher than that of DSSCs based on undoped TiO₂, respectively. The results of a variable temperature spectroelectrochemistry study show that the conduction band edge of 8 at% Sm-doped TiO₂ shifts positively. The lower conduction band position enhances the driving force of electrons and improves the electron injection efficiency from the lowest unoccupied molecular orbital (LUMO) of the dye to the conduction band (CB) of TiO₂, and the narrower band gap expands the response in the visible region and increases the utilization percentage of sunlight. These all contribute to enhancing the performance of cells based on an 8 at% Sm-doped TiO₂ photoanode. The as prepared Sm-doped TiO₂ material is proven in detail to be a better photoanode material than pure TiO₂.