Theoretical Exploration of a Di-Carbazole Based Dye for 3rd Generation Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) are known for their large potential in green, efficient and cost-effective solar energy technology. Therefore, investigating the solar-to-electricity conversion mechanism of photosensitizers in DSSCs can open up a new way for highly effective and stable solar cell devices. In this study, we used different molecular design strategies to develop various D-π-A photosensitizers based on dicarbazole. These approaches involved changing the positions of auxiliary acceptors and π-spacers as well as introducing new π-spacer units. To calculate the physical and electronic properties of these sensitizers, density functional theory (DFT) and time dependent density functional theory (TDDFT) were adopted. FMO analysis showed a significant charge transfer from the donor through the spacer to the acceptor which was also supported by DOS analysis. Energy gap of designed dyes have less than experimental Cz dye. NBO analysis has carried out the bond strength assessment and the studied molecule’s central nitrogen atoms related MOs. All the designed dyes exhibited good nonlinear optical (NLO) properties with maximum linear polarizability ⟨α⟩ amplitudes higher than first (βtotal) compared to the reference chromophore. Photovoltaic efficiency has been evaluated to electronic (Egap), open circuit voltage (VOC), short circuit current density (JSC), electron injection ability (∆Ginj), electron regeneration (∆Greg) and light harvesting efficiency.