Air-stable ambipolar organic field-effect transistors based on naphthalenediimide–diketopyrrolopyrrole copolymers

Two air-stable polymeric semiconductors were rationally designed and synthesized, namely PNDI-DPP and PNDI-T(DPP)T, containing naphthalenediimide (NDI) units and diketopyrrolopyrrole (DPP). The coplanar thiophene-substituted DPP moieties act as donors rather than acceptors, even though DPP is an electron-deficient core. In a bottom-gate/top-contact device architecture, the effect of changing the number of thiophene linkers on the performance of the two completely different OFETs was investigated. PNDI-T(DPP)T presented unipolar p-type behaviour with an average hole mobility of 0.02 cm(2) V-1 s(-1), while PNDI-DPP exhibited ambipolar transport with average electron and hole mobilities of 5.7 x 10(-3) and 1.6 x 10(-3) cm(2) V-1 s(-1), respectively. Moreover, OFETs based on the two polymers showed good air-stability with negligible changes after being stored under ambient conditions for over 3 months.