Organic solar cells (OSCs) based on non-fullerene acceptors have shown significant progress, with power conversion efficiencies (PCEs) now exceeding 13%, surpassing the best fullerene-based OSCs. Non-fullerene (NF) acceptors offer tunable absorption spectra and energy levels, enabling new opportunities for device physics and photophysics. They exhibit low voltage losses and high current generation, indicating new regimes of performance. However, challenges remain, including anisotropic structures and morphological control. NF acceptors, such as those based on fused aromatic diimides and strong intramolecular electron push-pulling effects, have shown high performance. For example, ITIC derivatives have been optimized for efficient charge separation and high PCEs. NF OSCs also demonstrate unique working mechanisms, with efficient charge separation even at low driving energies. Despite these advances, challenges such as non-radiative recombination and charge transport limitations persist. The development of NF acceptors provides opportunities for improved efficiency and practical applications, but further research is needed to address these challenges. NF OSCs show promise for future applications, particularly due to their thermal stability and potential for large-scale production. The review highlights the opportunities and challenges in NF OSCs, emphasizing the need for further investigation into material design, device engineering, and photophysical mechanisms to enhance performance and practicality.Organic solar cells (OSCs) based on non-fullerene acceptors have shown significant progress, with power conversion efficiencies (PCEs) now exceeding 13%, surpassing the best fullerene-based OSCs. Non-fullerene (NF) acceptors offer tunable absorption spectra and energy levels, enabling new opportunities for device physics and photophysics. They exhibit low voltage losses and high current generation, indicating new regimes of performance. However, challenges remain, including anisotropic structures and morphological control. NF acceptors, such as those based on fused aromatic diimides and strong intramolecular electron push-pulling effects, have shown high performance. For example, ITIC derivatives have been optimized for efficient charge separation and high PCEs. NF OSCs also demonstrate unique working mechanisms, with efficient charge separation even at low driving energies. Despite these advances, challenges such as non-radiative recombination and charge transport limitations persist. The development of NF acceptors provides opportunities for improved efficiency and practical applications, but further research is needed to address these challenges. NF OSCs show promise for future applications, particularly due to their thermal stability and potential for large-scale production. The review highlights the opportunities and challenges in NF OSCs, emphasizing the need for further investigation into material design, device engineering, and photophysical mechanisms to enhance performance and practicality.