Tuning optical and electronic properties in novel carbazole photosensitizers for p-type dye-sensitized solar cells

This work reports the synthesis and characterization of three novel carbazole-based push-pull dyes that have been purposely designed to be applied in p-type dye-sensitized solar cells (DSSCs). By using the same electron-donor moiety (the carbazole group) and three different electron acceptor groups, we explore how these new substituents affect the optical and electrochemical properties of the dye. State-of- the-art theoretical characterization at the DFT and TD-DFT levels of theory provides the means to un- derstand and elucidate the connection between the chemical composition, the structure and the elec- tronic features of these dyes. The interface between the dyes and the prototypical p-DSSC electrode (i.e. NiO) is also investigated by first-principles calculations, highlighting the importance of taking into ac- count the dye/electrode mutual polarization for a correct alignment of the relevant electronic states (e.g., dye HOMO and NiO valence band edge). Following these characterizations, preliminary studies on the photoelectrochemical performances of the new dyes in p-DSSCs provide promising results and motivate future investigations on these new systems.