Impact of side-chain engineering on the A-π-D-π-A type SM-BF1 donor molecule for bulk heterojunction and their photovoltaic performance: A DFT approach

Abstract

A hot topic in the field of photovoltaics is to minimize the energy loss during exciton dissociation by maximizing the balance between the acceptors and donors in the light-absorbing layer of organic solar cells (OSCs). For this reason, the bulk heterojunction (BHJ) with different blends of donor-acceptor materials is leading the research work in OSCs. We have introduced a series of eight novel donor molecules by the substitution of the terminal acceptor moieties on the A-π-D-π-A type reference molecule SM-BF1 (taken as R) that could be utilized in the blend of BHJ-OSCs. The frontier molecular orbitals, transition density matrix, density of states, molecular electrostatic potential, binding energy, excitation energy, maximum absorption wavelength, and some other photovoltaic attributes of the proposed molecules were analyzed through density functional theory and its time-dependent appoach. Though almost all of the newly derived molecules were a step up from the reference molecule in most of the studied characteristics, the F2 molecule seemed to conquer them all due to its desirable properties such as highest wavelength of maximum absorption (λmax), open-circuit voltage, fill factor, and lowest excitation and binding energy, etc. Also, the studied morphology, optical characteristics, and electronic attributes of the proposed molecules signified the fact that most of these molecules showed enhanced charge transfer, and could provide a maximum quantum yield of solar energy supplied.