A study reveals that trace oxygen in organic semiconductors (OSCs) plays a crucial role in their optoelectronic properties. Contrary to the traditional view that oxygen acts as a charge-carrier trap, this research shows that trace oxygen pre-empts donor-like traps, leading to p-type characteristics in most OSCs. This finding challenges previous assumptions and clarifies some previously unexplained phenomena in organic electronics. The study introduces a non-destructive deoxygenation method using soft plasma treatment, which effectively removes trace oxygen and alters the electronic properties of OSCs. De-doping results in the disappearance of p-type behavior and a significant increase in n-type properties, while re-doping under light irradiation in oxygen can reverse this process. This method allows precise modulation of key electronic characteristics such as polarity, conductivity, threshold voltage, and mobility, expanding the property space for all known OSC materials. The findings suggest that oxygen is an inherent dopant in OSCs, and its role in charge transport is more complex than previously thought. The study also demonstrates that oxygen doping can be reversibly controlled, enabling the modulation of OSC properties without damaging the materials. This research provides new insights into the intrinsic properties of OSCs and offers a promising approach for modulating charge transport in organic electronics.A study reveals that trace oxygen in organic semiconductors (OSCs) plays a crucial role in their optoelectronic properties. Contrary to the traditional view that oxygen acts as a charge-carrier trap, this research shows that trace oxygen pre-empts donor-like traps, leading to p-type characteristics in most OSCs. This finding challenges previous assumptions and clarifies some previously unexplained phenomena in organic electronics. The study introduces a non-destructive deoxygenation method using soft plasma treatment, which effectively removes trace oxygen and alters the electronic properties of OSCs. De-doping results in the disappearance of p-type behavior and a significant increase in n-type properties, while re-doping under light irradiation in oxygen can reverse this process. This method allows precise modulation of key electronic characteristics such as polarity, conductivity, threshold voltage, and mobility, expanding the property space for all known OSC materials. The findings suggest that oxygen is an inherent dopant in OSCs, and its role in charge transport is more complex than previously thought. The study also demonstrates that oxygen doping can be reversibly controlled, enabling the modulation of OSC properties without damaging the materials. This research provides new insights into the intrinsic properties of OSCs and offers a promising approach for modulating charge transport in organic electronics.