A series of bowl-shaped PDI dimers designed for organic photovoltaic cells through engineering N-annulated bridge towards potential alternatives of PDI bridged dimer acceptors

Perylene diimides (PDIs) dimer-based non-fullerene acceptors have made significant progress in the field of organic photovoltaics (OPVs) recently. To further render PDI derivatives soluble and tailor self-assembly, the incorporation of N-annulations in PDI dimers becomes an effective strategy in latest researches. Here, we focus on engineering PDI dimers with N-annulated bridges to construct bowl-shaped PDI dimers with the aim of improving efficiency, stereoscopic dimensions and the electron transfer abilities by introducing different functional linkers in N-annulated bridges. Besides some properties relevant to photovoltaic performance of these investigated acceptors were characterized based on density functional theory (DFT) and (time dependent density functional theory) TD-DFT calculations, Marcus semi-classical model was also employed to further estimate the exciton dissociation ability at D/A interface. Our results demonstrate that, compared to planar N-annulated PDI dimers, bowl-shaped PDI dimers possess higher LUMO energy levels, larger open circuit voltage (VOC), complementary optical absorption with the donor PBDTTT-C-T, and more effective charge separation at the interface. Moreover, we highlight that introducing SF and NDT linkers in N-annulated bridges would be more favorable to optical performance. We expect that these modified N-annulated PDI dimers could become potential acceptor materials in OPVs.