Abstract
Based on 3-(4-((4-carbazol-9-yl-phenyl)ethynyl)phenyl)-2-cyanoacrylic acid (CB1) dye, the six newly planned organic spacer (CBS1-CBS6) dyes were investigated for dye-sensitised solar cell (DSSC) application. The designed dyes have an electron-donor (D) in carbazole through a different pi-spacer and an electron-acceptor (A) in 2-cyanoacrylic acid. The density functional theory (DFT) and the time-dependent DFT (TD-DFT) evaluated the DSSCs of the molecules in the strategic platform. The results display that the TD-DFT method, using different functionals with exchange (XC) and long-range correlated (LC), was discussed. The electronic and optical properties of the CBS1-CBS6 dyes were discussed. The highest occupied molecular orbitals (HOMOs) and lowest unoccupied MOs (LUMOs) of the CBS1-CBS6 molecules can confirm the probable response to the regeneration and electron injection process. Also, the calculated results, such as injection driving force (Delta G(inject)), light-harvesting efficiencies (LHE), regeneration (Delta G(reg)) and open-circuit photovoltage (V-OC) of the CBS1-CBS6 sensitisers, were presented. A good contract of theoretical calculations with the literature data reveals a better understanding of the spacer's PV performance. To conclude, benzo[c][1,2,5]oxadiazole (CBS2) and [1,2,5]oxadiazolo[3,4-c]pyridine (CBS5) spacers were the best candidates for DSSCs, because of their smaller energy gap (E-g) and red-shifted absorption wavelengths.