The Molecular Synthesis And Devices' Fabrication Of Pentacene-like Organic Field Effect Transistor Materials

The importance and performance of organic electronic devices have both increased significantly over the last 20 years. Electronic devices based on organic semiconductor materials have already been demonstrated in areas such as light-emitting diodes, large-area sensor arrays, and solar cells. Organic semiconductors can be chemically modified to give desired electronic and processing characteristics as the active material in low-cost, large area electronics. Organic field effect transistors (OFETs), the basic unit of organic electronics, have been attracted increasing attention in recent years. The majority of OFET materials today are hole transporting materials. In contrast, there is a glaring lack of electron-transporting organic semiconductors. In this thesis, a series of organic semiconductor materials with different orbital energy have been designed and synthesized. The electronic transport properties of these molecules have been tailored to give desired electron transport properties.1. A series of soluble organic semiconductor materials have been designed and synthesized. By introducing the alkyl groups into pentacene backbone, we successfully synthesized a series of new pentacene derivatives with good stabilities and solubilities. Further chemical modifications, such as introduction of S and N atoms into the backbone, were carried out in order to tune the molecules' frontier orbital energy. The molecular structures have been confirmed by the NMR, MS and other spectroscopy. The molecular packing both in the single crystal and in the thin film have been investigated with X-ray diffraction and Atomic Force Microscopy.2. We have successfully fabricated the p-type OFETs based on pentacene and copper phthalocyanine as hole transport layer. The device's performance, such as hole transport mobility, on/off ratio and threshold voltage, has been studied. The relationship between the device performance and the different device structure has been exploited and the fabrication process has been optimized.3. Based on the results of experimental and theoretical study, a few newly synthesized organic semiconductor materials with good molecular packing and compatible frontier orbital energy were used to fabricate OFETs. Hole transport OFETs have been successfully obtained, and the effects of various fabrication parameters on the device performance have been studied. Full organic devices also have been obtained using ITO as gate electrode and polymer as insulating layer, instead of traditional Si/SiO2 structure.4. We demonstrated a new strategy for designing high-performance, ambipolar, acene-based field-effect transistor (FET) materials, which is based on the replacement of C-H moieties by nitrogen atoms in oligoacenes. Two new ambipolar materials with excellent transport properties have been obtained.