Quantum chemical designing of banana-shaped acceptor materials with outstanding photovoltaic properties for high-performance non-fullerene organic solar cells

Abstract

Non-Fullerene acceptors (NFAs) are getting a huge attention from the researchers across the globe to develop bulk-heterojunction organic solar cells (BHJ-OSC). In contrast with fullerene counterparts, the electronic energy levels as well as their optical properties can be tuned easily which ultimately helps to further enhance the power conversion efficiency of BHJ-OSC devices. By considering this crucial phenomenon of NFAs in OSCs, here we have designed a series of new banana-shaped NFAs (BS1-BS5) by doing end-capped modifications of BDTP-4F (R). Structural-property relationship, photo-physical, and optoelectronic properties of newly designed molecules are extensively studied by using density functional theory (DFT) and time dependent-density functional theory (TD-DFT). Furthermore, some geometric parameters like frontier molecular orbitals (FMOs), excitation and binding energy, hole-electron overlap, density of states, molecular electrostatic potential, open circuit voltage, transition density matrix, and reorganizational energy of electron and hole are also studied and compared with BDTP-4F (R). All of the designed materials (BS1-BS5) showed a red-shifting in absorption spectrum, higher electronic charge mobility, while, lower binding and excitation energies in-contrast to BDTP-4F. Much narrower HOMO-LUMO energy gaps (Eg= 1.89–1.98 eV) has been observed among all of the newly designed materials, suggesting their higher charge shifting behavior from HOMO to LUMO. In last, complex study of PTB7-Th/BS2 and PM6/BS2 also investigated in order to understand the charge shifting between donor and acceptor molecules. From all reported analysis, we concluded that our theoretical designed molecules are better than BDTP-4F (R), thus we recommend these molecules to experimentalist for future development of highly-efficient OSCs devices.