The article reviews the progress in developing non-fullerene electron acceptors (NFAs) for use in organic solar cells (OSCs). While fullerenes have been the dominant electron acceptors due to their ability to accept and transport electrons, NFAs offer advantages such as better tunability of absorption and electronic properties. The authors discuss the molecular design considerations and structure-property relationships that have led to the development of effective NFAs. They highlight the importance of factors such as tunable absorption, high extinction coefficients, and the ability to optimize the lowest unoccupied molecular orbital (LUMO) energy level. The review covers various classes of NFAs, including perylene diimide (PDI) and fused aromatic ring acceptors, rotationally symmetric molecules, and calamitic molecules. Each class is evaluated based on its performance in OSCs, with a focus on their structural characteristics and how they address the limitations of fullerene acceptors. The article concludes by emphasizing the potential of NFAs to enhance the efficiency and stability of organic solar cells.The article reviews the progress in developing non-fullerene electron acceptors (NFAs) for use in organic solar cells (OSCs). While fullerenes have been the dominant electron acceptors due to their ability to accept and transport electrons, NFAs offer advantages such as better tunability of absorption and electronic properties. The authors discuss the molecular design considerations and structure-property relationships that have led to the development of effective NFAs. They highlight the importance of factors such as tunable absorption, high extinction coefficients, and the ability to optimize the lowest unoccupied molecular orbital (LUMO) energy level. The review covers various classes of NFAs, including perylene diimide (PDI) and fused aromatic ring acceptors, rotationally symmetric molecules, and calamitic molecules. Each class is evaluated based on its performance in OSCs, with a focus on their structural characteristics and how they address the limitations of fullerene acceptors. The article concludes by emphasizing the potential of NFAs to enhance the efficiency and stability of organic solar cells.