A novel air-stable n-type organic semiconductor: 4,4′-bis[(6, 6′-diphenyl)-2,2-difluoro-1,3,2-dioxaborine] and its application in organic ambipolar field-effect transistors

Novel air-stable n-type organic field-effect transistors based on 4,4′-bis[(6,6′-diphenyl)-2,2-difluoro-1,3,2-dioxaborine] (DOB) have been fabricated. The devices exhibit a filed-effect mobility of 1 × 10^-4 cm² V^-1 s^-1, an on/off ratio of 10⁴ and a threshold voltage of 8.6 V at room temperature under ambient conditions. Moreover, ambipolar organic field-effect transistors based on DOB and copper phthalocyanine (CuPc) have been fabricated. Two device structures were adopted to investigate their transport properties. When devices were constructed with DOB as the first layer and CuPc as the second layer, they showed typical ambipolar transport properties. However, when the two layers were exchanged, the devices only showed p-channel transport properties. It is probable that CuPc, a bad electron transport material, blocks the electron transport to the DOB layer, leading to the disappearance of electron enhancement.