Molecular engineering of thienothiophene or dithienopyrrole-based π-spacers for dye-sensitized solar cells (DSSCs) with D-π-A architecture: A DFT/TD-DFT study

Abstract

The impact of divergent π-spacers including thienothiophene-2,5-dione (Ω1), thieno[3,4-b]thiophene (Ω2), thieno[2,3-b]thiophene (Ω3), or dithieno[3,2-b:2′,3′-d]pyrrole (Ω4) scaffolds linked with 2-phenylthiophene (Ψ1-2; differ from their binding order), 2,2′-bithiophene (Ψ3) or thiophene (Ψ4) subunits on the structural and photophysical properties of carbazole-based donor-π-acceptor type dyes were investigated by performing density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, respectively. According to the ground-state optimization and frequency calculations; ƐHOMO, ƐLUMO, bandgap (Ɛgap) energies, ionization potential (I), electron affinity (A), hardness (η), hyper-hardness (Γ), chemical potential (μ), dipole moment (μ), and electrophilicity index (ω) was determined. TD-CAM-B3LYP calculations were then used to enlighten light-harvesting efficiency (LHE), maximum absorbance wavelength (λmax), oscillator strength (f), excited-state lifetime (τ), the oxidation potential of the excited dye (εdye∗), the driving force (ΔGinject) of the electron injection, reorganization energy (ΔGregen), and open-circuit photovoltage (VOC) parameters.