A series of twelve Acceptor-π-Donor-π-Acceptor (A-π-D-π-A) topology-based donor molecules, where diketopyrrolopyrrole (DPP) as donor core unit is connected through furan which acts as conjugated π-bridge (CB) to aromatic derivatives (Ar) as acceptor units, have been investigated by making substitutions in acceptor units by using density functional theory(DFT) and time-dependent density functional theory (TD-DFT) for organic solar cell applications. The comparative study of optoelectronic properties indicates that thiadiazole with pyridine units containing molecules (M6b) exhibit lower energy of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels than those of oxadiazole and pyridine containing units (M6b). Among our investigated donors, the smallest Eg of 1.60 eV was observed for both M6a and M6b with distinctive broad absorption at 843 and 857 nm, respectively. Overall, smaller electron transfer (λe) values in contrast to hole transfer (λh) demonstrate that these donor compounds would be best for λe. The calculated open circuit voltage (Voc) is 2.45 and 2.17 eV, regarding bisPCBM and PC60BM (phenyl-C61-butyric acid methyl ester) acceptors. Thus, these theoretical calculations not only endorse the deep consideration between the chemical structures and optoelectronic characteristics of the donor-acceptor systems but also suggest appropriate materials for high-performance Organic Photovoltaics (OPV). Graphical abstract.
Keywords: Density of states; Diketopyrrolopyrrole; Optoelectronic properties; Organic solar cell; Small donor molecules.