Chemically dedoped PEDOT:PSS films with an amidine/polymer overcoating and their applications as a semiconducting channel in organic field-effect transistors and inverters

Abstract

We investigate the properties of a conducting polymer composite of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) after chemical dedoping with an amidine base and demonstrate the applications of the dedoped films as a semiconducting channel in a transistor and an inverter. We observe that PEDOT:PSS can be chemically transformed from a conductor to a semiconductor through a post-treatment with 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), which can donate electrons to the oxidized PEDOT chains and screen negative charges of PSS by salt formation. Both appearance of visible absorption bands and disappearance of (bi)polaronic absorption bands are observed in the DBN-treated PEDOT:PSS film, suggesting the effective dedoping. Compositional depth profiling and morphological analyses show that two distinct layers evolve after chemical dedoping and that the majority of internal PEDOT chains are dedoped over the whole film. We also introduce an overcoating layer using polyvinylpyrrolidone (PVP) with DBN to get more stable PEDOT:PSS films in a dedoped state. Organic field-effect transistors (OFETs) with the dedoped PEDOT:PSS film as a semiconducting channel show the typical p-type enhancement-mode characteristics without any doping-induced shift of threshold voltage. The pinch-off, hard saturation, and distinguishable switching characteristics with on-to-off current ratio of 104 are observed without redoping. We also demonstrate a logic circuit from the OFET as a proof-of-concept of semiconducting nature of PEDOT:PSS.