Computational investigations on efficient metal-free organic D-π-A dyes with different spacers for powerful DSSCs applications

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 π-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 $(\mathrm{\Delta }{G}_{\mathrm{inject}})$, light-harvesting efficiencies (LHE), regeneration $(\mathrm{\Delta }{G}_{\mathrm{reg}})$ 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.

KEYWORDS:

• D-π-A design
• CAM-B3LYP method
• XC and LC functionals
• LHE
• HOMOs-LUMOs energy levels

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors from KKU extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through Research Groups Program under grant number R.G.P.2/86/41.