Theoretical study of organic sensitizers based on 2, 6-diphenyl-4H-pyranylidene/1, 3, 4-oxadiazole for dye-sensitized solar cells

In this work, we theoretically studied ten organic dyes using the DFT and TD-DFT methods, where triphenylamine was used as the donor for the D1-D5 dyes, while the 2, 6-diphenyl-4H-pyranylidene donor was used for the D6-D10 dyes. Substituents (alkyl and methoxy) were also introduced into these donor groups. These dyes also include 1, 3, 4-oxadiazole and phenyl as a bridge pi and cyanoacrylic acid as acceptor. The electronic and optical properties of all dyes have been calculated as E-HOMO, E-LUMO, E-GAP, V-oc (the open-circuit photovoltage), lambda(max), E-ex, LHE (the light-harvesting efficiency) and Delta G(inj) (the free injection energy) in order to compare their performance as DSSC sensitizers. The donor effect of all dyes was discussed on the one hand and on the other hand the effects of the introduction of substituents (alkyl and methoxy) to the donor before and after binding to TiO2 cluster. The results show that the performance of the dyes using 2, 6-diphenyl-4H-pyranylidene as donor has improved compared with the rest of the dyes, which may improve the power conversion efficiency. Therefore, these dyes D6-D10 are good candidates for use as DSSC sensitizers.