A heterojunction consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl)))] (TFB) and aluminum tris(8-hydroxyquinolinate) (Alq3) is applied for fabricating an organic light-emitting photodetector (OLEP), where TFB and Alq3 behave as an ultraviolet response center and a green light emitter, respectively. The OLEP shows a detectivity of 1.4×1011 Jones and a luminance of 11,569 cd/m2. Thermal active delay fluorescent material is introduced in the TFB matrix to improve photodetection property. As a result, the optimized device exhibits a 2857% boost in a maximum detectivity of 4.0×1012 Jones without trading off the electroluminescence performance, exhibiting a high luminance of 13,737 cd/m2.