A DFT/TD-DFT Study of the Influence of Anchoring Group and Internal Acceptor of Benzocarbazole-based D-A´-π-A Dyes for DSSCs

Great attention is being shifted to Dye-sensitized solar cells because of their structural and electronic tunability, high performance, and low cost compared to conservative photovoltaic devices. In this work, the DFT/B3LYP/6-31G(d,p) and TD-DFT/mPW9PW91/6-31G(d,p) levels of theory are applied to the theoretical study of a new class of benzocarbazole-based D-A´-π-A dyes for their potential use in DSSCs. The influence of the internal acceptor on the optoelectronic properties is studied for the dyes. The optoelectronic and photovoltaic properties as HOMO, LUMO, Egap maximum absorption wavelength (λmax), vertical excitation energies (Eex), oscillator strength (f), light harvesting efficiency (LHE), open circuit voltage (Voc), injection force (ΔGinject), were evaluated and discussed in order to compare their performance as DSSC sensitizers. The theoretical results show that all dyes exhibit excellent optoelectronic properties, such as a lower Egap(1.733 eV to 2.173 eV), a significant λmax(631.48 nm to 754.40 nm), a sufficient value of Voc (0.461 V to 0.880 V) and high LHE (0.853 eV to 0.968 eV). In particular M4 with 2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dithione as auxiliary acceptor has the potential to be used as a sensitizer for DSSCs, due to its red-shifted absorption spectrum (λmax= 754.40 nm), and small energy gap (Egap=1.733 eV). Indeed, this study may help chemists to synthesize efficient dyes for DSSC.