Considering the thiophene unit as an electron-rich heterocycle, it is investigated with the aim of elucidating its potential efficiency for solar cell application. With the introduction of active substituents such as COOEt, CONH2 and CN into the thiophene segment, three novel thieno pyridine sensitizers (6a-c), based on donor-acceptor D-π-A construction, are designed and synthesized. The effect of the anchoring groups is investigated based on their molecular orbital's (MO's) energy gap (Eg). The electrostatic interaction between the synthesized dyes and metal nanoparticles, namely gold, silver and ruthenium, is believed to improve their performance as organic sensitizers. The dye-sensitized solar cells (DSSCs) are manufactured using the novel diazenyl pyridothiophene dyes, along with their metal nanoparticles conjugates as sensitizers, and were examined for efficiency improvement. Accordingly, using this modification, the photovoltaic performance was significantly improved. The promising results of conjugate (6b/AgNPs), compared with reported organic and natural sensitizers (JSC (1.136 × 10-1 mA/cm2), VOC (0.436 V), FF (0.57) and η (2.82 × 10-2%)), are attributed to the good interaction between the amide, methyl, amino and cyano groups attached to the thiophene pyridyl scaffolds and the surface of TiO2 porous film. Implementation of a molecular modeling study is performed to predict the ability of the thiophene moiety to be used in solar cell applications.
Keywords: HOMO-LUMO; dye-sensitized solar cells; metal nanoparticle; organic sensitizers; plasmonic; tetrahydrobenzothiophenes; thienopyridine.