Photoluminescence (PL)-based optical O2 sensors have applications in agricultural, medical and industrial areas. In this dissertation, All organic O2 sensors are realized by using organic light emitting diodes (OLEDs), porous O2 sensing film, and organic photo detectors (OPDs). The main idea is to create the voids in the O2 sensing film to have higher PL signal; and to modify the interfacial layer for organic photovoltaics (OPVs) to have higher sensitive photo detectors. This is a big step to have integrating small compact O2 monitoring platform. The modified porous sensing films also make it possible to have O2 and relative humidity (RH) monitored where less than 10% resolution in RH is obtained. This dual detection is important since those two parameters usually work together in the organic electronics device and food packaging. Furthermore, O2 monitoring can also be applied in the OLEDs or OPVs device, The active layer with the O2 sensitive material Pd octaethylporphyrin (PdOEP) can also be used as O2 sensing film. PL decay times of the active layer contain the information about the O2 trapping, and electroluminescence (EL) decay times of the OLEDs contain the information about the device degradation.