Designing Donor‐Acceptor‐Donor (D‐A‐D) Type Molecules for Efficient Hole‐Transporting in Perovskite Solar Cells – A DFT Study

Abstract We designed eight hole‐transporting materials (HTMs) of D‐A‐D type comprising an acceptor (A) unit flanked between two triphenylamine (TPA) donor (D) units. The structural, electronic, and absorption properties of designed molecules are studied using density functional theory (DFT) and time‐dependent DFT (TD‐DFT) methods. The MPW1PW91 functional with a 6‐31g(d,p) basis set was chosen, followed by a careful benchmark of DFT functionals. We identified dibenzothiophene‐triphenylamine (DBT‐TPA) and dibenzo‐1,4‐dioxaspiro[4,4]nonane‐triphenylamine (DBDN‐TPA) as the most promising molecules due to their unique properties, such as finite π‐conjugation, suitable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), deep blue absorption, and lower reorganization energy than the recently reported anthradithiophene–triphenylamine (ADT‐TPA) based HTMs. Furthermore, the newly proposed D‐(L‐A‐L)‐D type molecules with a linker (L) display the enhanced features required for improved hole mobility. Our work demonstrates the fine‐tuning of electronic interactions between the donor and acceptor units, with a linker (L), in achieving the planarity, absorption, and hole mobility essential for efficient HTMs in perovskite solar cells.