Non-fullerene electron acceptors are increasingly being used in organic solar cells (OPVs) to replace traditional fullerene acceptors. Fullerenes, while effective, have limitations such as poor absorption in the solar spectrum, difficulty in tuning energy levels, and tendency to crystallize, leading to device instability. New non-fullerene acceptors offer tunable absorption, improved solubility, and better energy level matching with donor materials, enhancing device performance. Perylene diimide (PDI) and fused aromatic ring acceptors have shown promise. PDI-based acceptors can be modified with functional groups to prevent crystallization and improve performance. For example, PDI dimers with twisted structures have been used to achieve high power conversion efficiencies (PCEs) in OPVs. Other acceptors, such as those based on truxenone and subphthalocyanine, have also demonstrated high PCEs due to their favorable energy levels and charge transport properties. Rotationally symmetric molecules, such as those derived from C60, have been developed for OPVs. These molecules offer tunable energy levels and good solubility, making them suitable for solution-processed devices. Corannulene and truxenone derivatives have shown improved performance compared to fullerenes, with some achieving PCEs over 7%. Calamitic molecules, with discrete electron-rich and electron-poor sections, have also been explored. These molecules can be designed to have optimal absorption and charge transport properties. For example, calamitic acceptors with a 3D structure have shown high PCEs due to their ability to form efficient charge-transport networks. The development of non-fullerene acceptors has led to significant improvements in OPV performance, with some devices achieving PCEs over 8%. These acceptors offer advantages such as enhanced optical absorptivity and easier tuning of frontier energy levels. However, challenges remain in achieving optimal phase separation and charge transport efficiency. Continued research into the structure-property relationships of non-fullerene acceptors is essential for further advancements in OPV technology.Non-fullerene electron acceptors are increasingly being used in organic solar cells (OPVs) to replace traditional fullerene acceptors. Fullerenes, while effective, have limitations such as poor absorption in the solar spectrum, difficulty in tuning energy levels, and tendency to crystallize, leading to device instability. New non-fullerene acceptors offer tunable absorption, improved solubility, and better energy level matching with donor materials, enhancing device performance. Perylene diimide (PDI) and fused aromatic ring acceptors have shown promise. PDI-based acceptors can be modified with functional groups to prevent crystallization and improve performance. For example, PDI dimers with twisted structures have been used to achieve high power conversion efficiencies (PCEs) in OPVs. Other acceptors, such as those based on truxenone and subphthalocyanine, have also demonstrated high PCEs due to their favorable energy levels and charge transport properties. Rotationally symmetric molecules, such as those derived from C60, have been developed for OPVs. These molecules offer tunable energy levels and good solubility, making them suitable for solution-processed devices. Corannulene and truxenone derivatives have shown improved performance compared to fullerenes, with some achieving PCEs over 7%. Calamitic molecules, with discrete electron-rich and electron-poor sections, have also been explored. These molecules can be designed to have optimal absorption and charge transport properties. For example, calamitic acceptors with a 3D structure have shown high PCEs due to their ability to form efficient charge-transport networks. The development of non-fullerene acceptors has led to significant improvements in OPV performance, with some devices achieving PCEs over 8%. These acceptors offer advantages such as enhanced optical absorptivity and easier tuning of frontier energy levels. However, challenges remain in achieving optimal phase separation and charge transport efficiency. Continued research into the structure-property relationships of non-fullerene acceptors is essential for further advancements in OPV technology.