Stud On Organic Field Effect Transistors Based On Pentacene-like Organic Molecules

Organic semiconductors have great potential in the applications like organic field effect transistors (OFETs), light-emitting diodes (OLEDs), photovoltaic cells. Compared with inorganic materials, organic semoconductors have advantages of great variety, wide resources, tunable electronic properties and flexibility. However, there are still some challeges for organic semiconductors to substitude for inorganic materials. Invesitigations on the structure-property relationships of organic semiconductors will provide useful information for further research on high performance organic devices.In this thesis, we have investigated the OFET properties of different pentacene-like organic semiconductors. CMOS-like inverter based on an ambipolar organic semiconductor material using different electrodes were fabricated. We then discussed the effects of using organic material as electrode buffer layer.The thesis includes the following parts:Chapter1Current developments and the prosperity of organic semiconductor materials have been reviewed. Three types of organic semiconductor materials were described. Techniques and principles associated with the fabrication of OFET devices using these materials have been discussed.Chapter2A series of new organic semiconductors based on s-indaceno[1,2-b:5,6-b’] dithiophene-4,9-dione have been investigated for their OFET performances. The results indicate that, introduction of thiophene and carbonyl group into heteroacence framework is an efficient mean to obtain semiconductor material. It is found that different alkyl groups will result in different transport properties. Meanwhile, the deposition temperature would also affect the OFET performances.Chapter3We have investigated the OFET performances of a serials of N-heteropentacenes, which contain different N-atoms and halogen atoms. Introduction of N-atoms or halogen atoms can efficiently lower the LUMO level and obtain the ambipolar organic semiconductors. We have selected e4Cl-1N-T-pen for our further studies.Chapter4We fabricated OFET and complementary metal-oxide semiconductor (CMOS) logic based on an ambipolar organic material (4Cl-1N-T-pen). The OFETs with different electrodes showed good performances. When using Ag and Au as the electrodes, both the electron and hole mobilities were above0.2cm2V-1s-1. The complementary circuits based on these OFETs exhibited ideal behaviour characterized by very high voltage gains (>160).Chapter5The ambipolar organic semiconductor,4Cl-1N-T-pen, were used as the buffer layer for source and drain electrodes of different OFETs. The results indicated that using4C1-1N-T-pen as buffer layer will improve the performance of OFET devices based on p-type semiconductor Tips-Pen and n-type semiconductor C12-CN. The mobilities were raised and the threshold voltages were lowered.