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

Herein, we report the design and synthesis of four new thiophene-bridged D-π-A configured organic dyes T1-4 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 T1-4 display λabs and λemi in the range of 400-470 nm and 550-580 nm, respectively, with a bandgap in the order, 2.31-2.58 eV. Further, 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. Further, their co-sensitized devices were fabricated by co-adsorbing them with well-known Ru-based MH-12 sensitizer and interestingly the co-sensitizer T3 carrying an alkoxy group and barbituric acid anchor displayed the highest PCE of 8.79%, which is much higher than 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.