Theoretical study of electronic structure and excited states properties of two dyes for dye-sensitized solar cells

Two conjugated organic dyes comprising the benzo[b]furan moieties as the electron donor and cyanoacetic acid moieties as the electron acceptor/anchoring groups have been investigated using a quantum chemical method. The molecular equilibrium geometries and ground state character were studied using density functional theory. Absorption spectra were obtained using time-dependent density functional theory and semiempirical ZINDO. The nature of absorption spectra was further studied using 2D and 3D real-space analysis; here, 2D real-space analysis showed electron–hole coherence, and 3D real-space analysis showed intramolecular charge transfer during photo-excitation. As important parameters, excited state oxidation potential and driving force energy were obtained to reveal the relationship between molecular structure and performance of two compounds.