Exploring the Applicability of Novel Indolic Semiconductors in Dye-Sensitized Solar Cells: Theoretical Forecasting and Assessment of Electron Injection into TiO2

Molecular modelling using quantum methods (DFT/TD-DFT) was performed to carry out the simulation of the geometry and electronic structure of indole-based photosensitizers. Remarkably, the close agreement between our computed results for the dyes (M1–5) and experimental data highlights the robustness of our computational approach, affirming its utility for further research and development. A particularly intriguing observation was the noticeable shift in UV-visible spectra towards the infrared region for all the dyes, associated with their higher extinction coefficients compared to the reference molecule R. This spectral shift suggests the potential of these photosensitizers to capture and exploit infrared light in THF solvent. Strong interactions witnessed between the dyes and the (TiO2) surface strongly affirm the potential of these compounds to enhance the electron injection process. This affirmation is further substantiated by our examination of the HOMO spatial distribution, which demonstrates the predominant localization of electron density within the dye molecule, and the LUMO spatial distribution, which vividly illustrates the concentration of electron density on the (TiO2)9 surface. Based on the findings presented herein, it is plausible to consider these selected dyes as potential enhancers for this type of solar cell, owing to their redshift and alignment with the conduction band of TiO2.