Low-cost Schiff bases chromophores as efficient co-sensitizers for MH-13 in dye-sensitized solar cells

Herein, we reported on the synthesis of four Schiff bases (S_1–4) based on salicylaldehyde moieties and their applications as metal-free organic chromophores for sensitization and co-sensitization of dye-sensitized solar cells (DSSCs). These sensitizers are comprised of a phenyl ring as a donor scaffold connected with a carboxylic group as acceptor/anchoring unit. To gauge their applicability as photosensitizers for DSSCs the photophysical, electrochemical, theoretical studies and charge transport characteristics were carried out. Interestingly, uses of S₂ and S₄ dyes as co-sensitizers with well-known MH-13 dye resulted in enhancing its photovoltaic properties from 8.217 to 8.79% and 8.48%, respectively. Furthermore, the photo-sensitizer S₃ individually shows better photovoltaic properties compared to S₁, S₂ and S₄, due to the fast photo-induced electron transfer from the phenyl ring to the nitro group. This fast electron transfer resulted from the overlapping between HOMO and LUMO levels on phenyl ring bearing nitro group. The results indicate that these simple and easy prepared Schiff bases moieties may be considered as promising and low-cost co-sensitizers for DSSCs.