Amare Benor Belay

• Flexible and lightweight electronics realized on large areas has gained considerable attention in recent years. The interest is particularly generated by the wide demand in low cost large area displays, smart cards and radio frequency identification tags (RFID) and the like. Such electronic devices can only be realized at low cost if novel material systems and new ways of fabricating the devices and systems are developed. Organic semiconductors are a very promising material system used for such applications. Organic materials and organic electronic device components can be printed, which allows for large area processing at low fabrication cost. Thus, organic semiconductors and printing methods are required to attain the desired low cost, and/or large electronic devices. In this study, organic thin film transistors (TFTs), which are key elements of organic electronic devices like RFID tags, flexible display media and smart tags are investigated. Pentacene, an organic semiconductor, is investigated as active materials in thin film transistors. The electrodes of the transistors are fabricated by microcontact printing. Microcontact printing is a method in which a self-assembled monolayer is used to functionalize, modify or pattern surfaces or films. In the study, new microcontact printing based methods were developed, which use self-assembled monolayer as dewetting agent. Next, the printing method was applied to fabricate pentacene TFTs. Furthermore, the device performance of the TFTs prepared by printing methods are studied and compared with transistors prepared by conventional optical lithography. Finally, the environmental and electrical stability the pentacene transistor was studied.