Synergistic end-capped engineering on non-fused thiophene ring-based acceptors to enhance the photovoltaic properties of organic solar cells

Abstract

In this study, a series of non-fused thiophene ring-based small molecular acceptors (4T1–4T7) of A-D-A type are developed by the replacement of the end-groups of the 4TR molecule. The optoelectronic characteristics of the 4TR and 4T1–4T7 molecules are investigated employing the MPW1PW91 functional with the 6-31G (d,p) basis set, and solvent-state computations are studied using the TD-SCF. All the parameters estimated in this research are improved to a substantial level for the developed molecules as compared to the 4TR molecule, e.g. all the newly developed molecules have shown a red shift in their maximum absorption (λ_max) and a reduced bandgap compared to the 4TR molecule, with ranges of 646 nm to 692 nm (in chlorobenzene solvent) and 2.34 eV to 2.47 eV, respectively. The reorganization energies of electron and hole mobility for almost all developed molecules are smaller than those for the 4TR molecule, with ranges of 0.00766–0.01034 eV and 0.01324–0.01447 eV, respectively. Hence, all the modified chromophores exhibit better charge capabilities than the 4TR molecule. The charge mobility of almost all the developed molecules is improved because of their reduced reorganization energies. The 4T2 molecule has minimum RE values for both electrons (0.00766) and holes (0.01324). The V_OC values of all acceptor molecules are calculated with respect to the PTB7-Th donor. An elevation in V_OC and FF values is exhibited by the 4T5 and 4T7 molecules. As a result, these end-capped engineered molecules should be proposed for the future manufacturing of highly efficient organic solar cells.