Incorporation of Heteroatoms in Conjugated Polymers Backbone toward Air-Stable, High-Performance n-Channel Unencapsulated Polymer Transistors

Organic field-effect transistors (OFETs) without any encapsulation of polymer semiconductor layers that still exhibit unipolar n-type characteristics under air conditions are very rare. In this study, we use fluorinated bithiophene as a donor, and bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF, P1) and aza-substituted BIBDF (P2) as acceptor units to develop air-stable and unipolar electron transport polymer semiconductors. Unencapsulated OFETs based on P1 and P2 were fabricated and directly evaluated under air conditions. The highest effective mobility (μe,maxeff) of 0.23 cm2 V–1 s–1 was obtained for P2-based devices with high Ion/Ioff ratio of >106 and low threshold voltage of 1.1 V. Moreover, P2 had high air stability and maintained unipolar electron transport with μe,maxeff of up 0.1 cm2 V–1 s–1 and Ion/Ioff ratio of >106 during the 60 days of air storage. The work provides an effective molecular design strategy to develop air-stable and high-performance n-channel unencapsulated polymer transist...