Simple thiophene-bridged D–π–A type chromophores for DSSCs: a comprehensive study of their sensitization and co-sensitization properties

Abstract

Herein, we report the design and synthesis of four new thiophene-bridged D–π–A configured organic dyes T_1–4 comprising different donors, π-spacers and anchoring units, as potential sensitizers and co-sensitizers for DSSCs. The current work also highlights their structural, photophysical, thermal, electrochemical, theoretical, and photoelectrochemical studies, including evaluation of their structure–property relationships. The optical results revealed that the dyes T_1–4 display λ_abs and λ_emi in the range of 402–461 nm and 556–575 nm, respectively, with a bandgap in the order of 2.31–2.58 eV. Furthermore, the results showed that the dyes possess all the pre-requisites to act as sensitizers/co-sensitizers. Among the tested dyes, the device based on sensitizer T₂ achieved the highest PCE compared to the other three dyes, under the standard conditions. Furthermore, their co-sensitized devices were fabricated by co-adsorbing them with the well-known Ru-based MH-12 sensitizer and interestingly the co-sensitizer T₃ carrying an alkoxy group and a barbituric acid anchor displayed the highest PCE of 8.79%, which is much higher than that of MH-12 alone (8.18%). Conclusively, the study furnishes a deeper understanding of the intricacies involved in the structural modification of sensitizers/co-sensitizers in achieving an enhanced performance of the devices.