New photosensitizers that are based on carbazoles and have thiophene bridges with a low bandgap do 32% better than N719 metal complex dye

[Display omitted] •Highlights for publication in Journal of Photochemistry and Photobiology A: Chemistry.•Four carbazole organic dyes (MES1-4) with a D-π-A architecture were synthesized for dye-sensitized solar cells.•The study of the dihedral angle and the NBO studies showed that ICT works well within the structure of MES1-4.•Using MES1-4 as sensitizers results in a higher photovoltaic efficiency with a range of 6.06–9.55%.•The MES4 has the highest light harvesting ability owing to the existence of distinct anchoring groups.•The PCE of the DSSC based on MES4 yields a promising PCE of 9.55% and a score that is 32% higher than that of the N719. Synthesis of metal-free organic sensitizers is a promising route for obtaining low-cost, high-efficiency sensitizers for dye-sensitized solar cells (DSSCs). We present the results of a comprehensive photovoltaic analysis of four carbazole organic sensitizers with a D-A architecture in this study. MES 1-4 have been developed and used as sensitizers in DSSC applications. Using MES1-4 as sensitizers results in a broader light-harvesting ability (400–800 nm) and higher photovoltaic efficiency at a range of 6.06–9.55 %. Herein, the introduction of thiazolidine-4-one ring engineering into MES4 as a rich electron acceptor enhanced electron injection and inhibited electron recombination in thiazolidine-4-one sensitizers. The MES4 system has the highest light harvesting ability and reflectivity owing to the existence of distinct functional groups that enhanced the capacity to bind the dye with the semiconductor layer (TiO2 device's efficiency). In conclusion, the DSSC using the novel electron acceptor thiazolidine-4-one ring sensitizer achieves an unexpected PCE of 9.55 % and a 32 % increase over using the N719 metal complex dye. All sensitizers based on carbazole compounds had good photovoltaic performance.