Pentacene Based Organic Thin Film Transistors as the Transducer for Biochemical Sensing in Aqueous Media

Organic thin-film transistors show tremendous potential for versatile electronic sensors. Critical challenges facing the integration of organic thin-film transistors (OTFTs) as chemical and biological sensors include reproducibility, sensitivity, and particularly stability. Here, we describe a bilayer organic semiconductor structure consisting of a pentacene active layer with copper phthalocyanine as the top surface passivation layer. In this architecture, the copper phthalacyanine (CuPc) acts as a surface passivation layer with efficient charge injection into the pentacene layer, thus providing a versatile method for the incorporation of many semiconductor materials as the sensing element. OTFTs fabricated with the described structure exhibited a field-effect mobility of 1.15 ± 0.2 cm 2 V −1 s −1 at −2 V in ambient conditions with stable performance in aqueous media (0.5 cm 2 V −1 s −1 at −1 V). X-ray diffraction (XRD) confirms that the bilayer film achieves a high degree of molecular order as suggested by the high OTFT mobility. OTFTs based on the pentacene/CuPc bilayer films were fabricated on both rigid silicon and flexible polyimide substrates. The aqueous buffer stability of these devices was exploited for the detection of chemical and biological species.