The present invention relates to a structure of photodiode, which comprises a substrate, a first electrode, an electron transport layer, a photoactive layer, a filter layer, and a second electrode. The first electrode is disposed on the substrate. The electron transport layer is disposed on the first electrode. The photoactive layer is disposed on the electron transport layer. The photoactive layer has a first energy gap value. The filter layer is disposed on the photoactive layer and has a second energy gap value. The second electrode is disposed on the filter layer. The second energy gap value is greater than the first energy gap value. The ratio of the second energy gap value to the first energy gap value is an energy gap ratio. The energy gap ratio is greater than 1 and less than or equal to 3.