The most common type of organic photodetector is the organic photodiode (OPD). The photodiode has a simple structure in which an active layer is sandwiched between a transparent electrode and a metal electrode. In contrast to OLEDs, organic photodiodes (OPDs) utilize the organic semiconductor to absorb incident light and convert it to electric current. The structure and working principle are more like organic solar cells. Among the various organic photodetectors, organic photodiodes (OPDs) have been the most widely studied due to their fast response, high sensitivity, and full use of the existing research base of organic photovoltaics (OPVs).