Involvement of halogen and polyaromatic substituents in chalcone derivatives as dye sensitizers in solar cell applications

A series of pyrenyl and halogenated chalcone (PyBr and PyF) derivatives with different substituent groups have been constructed in this work for dye-sensitized solar cell (DSSC) applications. The compounds were synthesized using the Claisen-Schmidt condensation reaction and single crystals were successfully attained via the slow evaporation method. The existence of intermolecular interactions (C-H center dot center dot center dot O, C-H center dot center dot center dot pi and pi center dot center dot center dot pi) in crystal packing was found to stabilize the crystal structure and enhance charge transfer within the molecules. UV-Vis analysis was conducted with the acetonitrile solvent to obtain the energy gap values of PyBr and PyF, which were particularly in the range suitable for photosensitizer materials used in DSSC (2.74 and 2.78 eV). The proposed compounds are situated in the appropriate HOMO and LUMO energy levels, confirming their suitability as dye sensitizer materials. Further, all compounds were investigated for solar cell performance. The fabrication of the DSSC layers was carried out and characterization using the FESEM-EDX analysis revealed the surface morphology and elemental composition of the compounds on the TiO2 layer. Owing to the D-pi-A architecture and planar structure of PyBr, the compound showed an improved performance in DSSC compared with the twisted structure of PyF with the additional methoxy group.