Ambipolar all-polymer bulk heterojunction field-effect transistors

Abstract

We demonstrate solution processable all-polymer based field-effect transistors (FETs) exhibiting comparable electron and hole mobilities. The semiconducting layer is a bulk heterojunction of poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (n-type polymer) and regioregular poly(3-hexylthiophene) (p-type polymer). These polymers form a type-II heterojunction as revealed by the faster photoluminescence dynamics of the blend compared to the pristine materials. An electron mobiliy of 4 × 10⁻³ cm²/V s and a hole mobility of 2 × 10⁻³ cm²/V s were extracted from the transfer characteristics of bottom contact FETs. The balanced mobilities suggest that the active layer is a fine network of the two components, as confirmed by atomic force microscopy phase images.