Organic field-effect transistors for sensing applications

PhD ceremony: Mr. F. Maddalena, 16.15 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Organic field-effect transistors for sensing applications

Promotor(s): prof. D.M. de Leeuw, prof. P.W.M. Blom

Faculty: Mathematics and Natural Sciences

The thesis focuses on the study of organic field effect transistors and their usefulness for (bio)sensing applications. The research is more focused toward fundamental understanding of the use of the OFET as a sensor or biosensor rather than realization of the sensors itself.

Chapters 1 and 2 give a general introduction in the field of organic electronic devices and describe the materials and experimental methods used throughout the thesis.

Chapter 3 gives the characterization of the device operation of dual-gate organic field-effect transistors (DG-OFET), fabricated by solution processing. It is shown that the threshold voltage of the bottom gate of the devices depends on the top gate bias with two linear relationships for two different regimes.

Chapter 4 describes the fabrication and testing of the 'Bio-FET', an organic field-effect transistor-based biosensor for the detection of sulphate ions. The Bio-FET uses a dual-gate structure where the top-gate electrode is replaced by a protein layer which captures the sulphate ions. The binding of sulphate ions in dry conditions was detected by a shift in the threshold voltage.

Chapter 5 investigates the kinetics of acid doping of regio-regular poly-3-hexylthiophene in field-effect transistors. The dopant density was extracted from field-effect transistors, as a function of temperature and exposure time. The change in dopand density in time was phenomenologically described by stretched exponential time dependence.

Chapter 6 investigates the charge carrier mobility dependence on the charge carrier density in semiconducting polymers in diodes and transistors.