Designing of symmetrical A-D-A type non-fullerene acceptors by side-chain engineering of an indacenodithienothiophene (IDTT) core based molecule: A computational approach

Abstract

Recently, non-fullerene organic solar cells (OSCs) have shown efficiency values exceeding 18%. They have shown tremendous improvements in the last decade and are now about to enter the commercial market due to their unique properties. In order to enhance the photovoltaic efficiency of ITC-2Cl molecule of the ITC series, four new molecules with an A-D-A architecture were designed. All the molecules were derived from the heptacyclic fused ringed indacenodithienothiophene core of the reference molecule by substituting various effective acceptor moieties in its structure. The computational studies of all the molecules were carried out to reveal their various structural, optoelectronic, and photovoltaic properties. All the newly altered molecules, except for one (ITC-M1), demonstrated an increase in value of λmax, a reduced bandgap that is in accordance with the one required for organic photovoltaic cells, superior electronic distribution pattern, lowered excitation energies, significant intramolecular photo-induced charge transport, and greater ground as well as excited state dipole moment. Moreover, the density of states (DOS) and transition density matrix (TDM) analyses supported the findings of the newly designed molecules having better attributes of charge transportation as opposed to the reference molecule (ITC-2Cl). Moreover, ITC-M4, ITC-M3, and ITC-M2 could perform better in terms of the mobility of electrons due to their low electron reorganization energies. In addition, the parameters directly affecting the computed photovoltaic efficiency of any organic solar cell (the fill factor, open-circuit voltage, the normalized VOC, etc.) seemed to be the highest of all, for the ITC-M1 acceptor molecule. So overall, the results of this study suggested that all the newly designed molecules have great potential in constructing highly proficient OSCs in bulk-heterojunction.