Tuning the electronic structures and related properties of phenothiazine-based donor-π-acceptor dyes for dye-sensitized solar cells: a theoretical study

Two phenothiazine-based organic D-pi-A dyes V5 and V7 used in DSSCs with difference in pi spacer were theoretically studied and verified using density functional theory and time-dependent density functional theory to shed light on how the pi spacer influences the performance of the dye. The change of short-circuit current density (J (SC)) and open-circuit photovoltage (V (OC)) between V5 and V7 was demonstrated by means of the light-harvesting efficiency and the energy differences eV (OC) between E (LUMO) and E (CB), respectively. A novel dye namely VX was designed by replacing the thiophene unit in V7 with an electron-rich 3,4-ethylenedioxythiophene unit. The theoretical results revealed that compared with V7, the VX dye is expected to show better performance in the DSSC field.