DFT and TDDFT Studies of Non-Fullerene Organometallic Based Acceptors for Organic Photovoltaics

Abstract

Recently, non-fullerenes acceptor based solar cells have replaced the fullerenes based ones due to their higher enhanced photochemical and thermal stability. Hence, in this work, six molecules based on D–A and D–A–D topologies have been designed, where dipyridophenazine as acceptor (which is attached with a metal atom) is attached with triphenylamine as the donor fragment. In case of D–A topology based A1–A3 molecules, donor: acceptor ratio is 1:1 while in D–A–D type B1–B3 molecules it is 1:2. Computational analyses based on density functional and time-dependent density functional are carried out to investigate the effect of Ca, Mg, and Be metals in both topologies. Reduced orbital energy levels in all designed molecules refer to them as good acceptors in both topologies. Ca-complexed (A1 and B1) acceptors in both topologies after the optimal function have shown a smaller energy gap of 0.6 eV than those of reference R and all other designed molecules. In case of D–A–D topology, B1 showed a significant red-shift of 72 nm than that of R. While D–A topology-based A1 showed a more or less similar absorption wavelength like R. Besides, absorption peaks of Mg and Be-complexed molecules are stronger in the case of D–A–D topology. In a nutshell, this computational investigation approved these molecules as efficient and effective for non-fullerene organometallic based acceptors for organic solar cell devices.