Dicyanoimidazole (DCI) and Dicyanobenzoimidazole (DCBI) based D-π-A organic dyes as next-generation acceptors for...

This article introduces a set of ten newly developed D-π-A organic dyes E (1-10), each tuned to improve light harvesting and charge transfer for DSSC applications. These dye molecules have a dithieno[3,2-b:2',3'-d]thiophene π-bridge, flanked by electron-donating groups: amino, dimethylamine, methoxy, or diphenylamine and a diverse set of electron-withdrawing acceptors including nitro (-NO₂), cyano (-CN), Cyanoacrylic acid (CAA), 4,5-dicyanoimidazole (DCI), and 5,6-dicyanobenzoimidazole (DCBI). To ensure the reliability of the selected computational methods for both DFT and TD-DFT studies, computed results has also been compared with the experimental maximum absorption wavelengths (λ_max) obtained for the reported reference dye molecule, which includes dithieno[3,2-b:2',3'-d]thiophene as the π-conjugated spacer. The computed results reveal that these dye molecules have relatively narrow energy gaps (E_g) (2.56 eV - 4.09 eV) and strong intramolecular charge-transfer (ICT) behaviours, with absorption maxima (λ_max) ranging up to 610.3 nm. Substituting the typical CAA acceptor with DCI or DCBI greatly improves hole injection and strengthens ICT interactions. This modification results in a red-shifted absorption and higher molar extinction coefficients. The predicted open-circuit voltage (V_oc) ranges from 0.94 V to 1.36 V, while the light-harvesting efficiencies can reach up to 93.83 %. The photovoltaic analysis demonstrates excellent device performance, with short-circuit current densities (J_SC) reaching 35.2 mA cm^-2 and power conversion efficiencies (PCE) up to 37.1 %. Overall, these findings highlight the proposed dyes as high-efficiency sensitizers for next-generation DSSC applications.