Air stable ambipolar organic field-effect transistors containing p/n heterojunctions are achieved by passivating the electron trapping sites on the SiO2 surface. The morphology of the heterojunctions is controlled by the film thicknesses of p- and n-channel semiconductors, thereby affecting the device air stability and the electrical characteristics. Further, air stable complementary-like inverters, which are able to work both in the first and the third quadrants with a high gain up to 30, are also demonstrated.