Recently, the development of non-fullerene electron acceptor materials shows a significant progress in the field of organic photodiodes such as solar cells and photodetectors. With the advantage of being able to finely tune the optical bandgap based on the possibility of flexible structural modification, it enables various applications such as high-performance semitransparent device platform, indoor energy harvesting, and wavelength-selective photodetection, which were difficult to implement in conventional solar cells. In this review, we would like to discuss the latest research trends of organic semiconducting materials used in the photoactive layer of organic photodiodes.