Rational design of fused-ring based non-fullerene acceptors for high performance organic solar cells

In this study, we have designed 56 new non-fullerene acceptors (NFAs) by rational design of end-cap manipu-lation and core modification using density functional theory methods. Geometrical, electronic, and excited state properties of these newly designed molecular are thoroughly characterized using the state-of-the-art density functional theory methods. The influence of end-cap groups on various core units is studied by comparing the absorption wavelengths, lowest excitation energies, ground-state dipole moments and, excited state dipole moments. Results obtained from these analyses reveal the importance of choosing the right combination of end -cap and core units. The potential NFAs are screened using selection criteria such as energy gap between the LUMO of polymer donor and the LUMO of NFA, based on the energy difference between LUMO and LUMO + 1 of NFAs, energy gap between the HOMO of polymer donor and LUMO of NFA, dipole moments, and quadrupole moments of NFA. Furthermore, donor-acceptor interfaces are constructed using potentials NFAs and the PM6 polymer donor. Charge-transfer state, exciton dissociation, and charge separation processes are analyzed at the polymer/NFA interfaces. Overall, results obtained from these analyses provide valuable guidelines for designing potential NFA that could enhance photovoltaic devices' efficiency.