Unveiling the role of peripheral acceptors in ortho-benzodipyrrole-based chromophores for efficient performance in organic solar cells: A comprehensive theoretical study

The exploration of novel non-fullerene acceptor (NFAs) materials for organic solar cells (OSCs) is a frontline area of research. Herein, novel A–π–A chromophores (CBR and CBD1-CBD6) were proposed with reduced energy gaps and improved intramolecular charge transfer (ICT) rates. The ortho-benzodipyrrole was incorporated as the central core, end-capped with strong malononitrile acceptors. The density functional theoretical (DFT) approach was adopted at the M06/6-311G(d,p) level to explore the structure-property relationship, opto-electronic, and photovoltaic (PV) properties of these NFA-based compounds. The suitability of these chromophores for OSCs applications was confirmed by performing their frontier molecular orbitals (FMOs), transition density matrix (TDM), density of states (DOS), UV-Visible, hole-electron, open circuit voltage ( V oc ), fill factor (FF), and power conversion efficiency (PCE) at the afore-mentioned level. The outcomes of these analyses showed that modifying the terminal acceptors with electron-withdrawing groups significantly lowered the energy gaps (2.20-2.34 eV ) of the designed chromophores (CBD1-CBD6) as compared to the CBR reference (2.371 eV ). They also showed broader absorption wavelengths (654.75-724.03 nm ) with correspondingly lower excitation energies (1.71-1.89 eV ). Interestingly, CBD3 showed the most promising results, i.e., minimal highest-occupied molecular orbital (HOMO)/lowest-unoccupied molecular orbital (LUMO) energy gap (2.20 eV ), along with high λ max (724.03 nm ), and least excitation energy (1.71 eV ). All the proposed compounds showed significant open-circuit voltage ( V oc ) (2.334-2.694 V ) and fill factor (FF) (0.937-0.946) values. Consequently, these compounds also possessed greater PCEs, which provides a deep insight into their high charge transfer ability and PV efficiency. Overall, this study is useful in exploring new NFA-based OSCs for high-tech applications.