A multifactorial DFT study of acceptor-tailored carbazole-based dyes with potential relevance to indoor DSSCs

This work presents the computationally guided design of ten acceptor-engineered D-π-A dyes (J1-J10) derived from a reference carbazole-phenothiazine dye (J) for DSSC applications with possible relevance to indoor photovoltaics. The engineered dyes demonstrate tunable optoelectronic properties compared with the reference. Notably, J2 achieves the smallest HOMO-LUMO gap (1.13 eV) and lowest exciton binding energy (0.01 eV), while J6 shows a red-shifted optical response; however, their LUMO levels lie below the TiO₂ conduction band, limiting their suitability as sensitizers. A combined analysis of key molecular-level descriptors, including energy-level alignment, charge-transport behavior, and adsorption stability, identifies J10 as the most balanced sensitizer candidate in the designed series. J10 exhibits a favorable LUMO position for electron injection, a reduced HOMO-LUMO gap of 2.16 eV, favorable charge-transport-related descriptors, and favorable dye-TiO₂ interaction, suggesting its potential for future experimental evaluation as a DSSC sensitizer. This work highlights the role of acceptor engineering in tuning carbazole-based sensitizers and provides theoretical guidance for future DSSC dye design with possible relevance to indoor photovoltaic applications.