The Study Of Interface Performance In Organic Thin Film Transistor

It is one of the key development direction in the field of electronics to preparation electronic components, such as transistors, on flexible substrate and then construct a flexible electronics in the future. While electronic products based on inorganic transistor general show poor flexibility and most of them prepared on the rigid substrate. The emergence of the organic thin film transistor (OTFT), provides feasible ideas to solve the development problem of inorganic transistor. Organic thin film transistors with the advantages, such as flexibility, solution process, sufficient material sources, low cost, etc., have attracted great interest, which make up the deficiency of the inorganic transistor.At present, the mobility of organic thin film transistor has reached the level of practical application. However, a wide range of charge-carrier mobilities has been reported by a number of research groups for the same organic semiconductor. For example, the reported mobilities of pentacene OTFTs range from 0.03-6.3 cm2 V-1 s-1, the reason of which may be that the differences of preparation technology and device structure. During the working of OTFT, the injection and transport of charge carriers determines the performance of the device. The injection and output of charge carrier depends on the interfaces between the electrodes and organic semiconductors, and which determine the generation of contact resistance. While charge carrier transport on the interfaces between organic semiconductors and dielectric layers, the roughness and defects in which have a important influence on the carrier transport and the mobility of the device. Therefore, the quality of interfaces directly decides the device performance in organic thin film transistors. It's a main topic to optimize the interfaces in the OTFT, whether for theoretical or technological research. In this paper, we study the interfaces between the electrodes and organic semiconductors, and the interfaces between organic semiconductors and dielectric layers in OTFT.Firstly, we study the interfaces between the electrodes and organic semiconductors. Electrodes, one of the key components of organic thin film transistor (OTFT), exert great influence on the device performance as well as the circuit fabrication. Conventional metal electrode generally shows poor contact quality with organic semiconductors especially in bottom-contact geometry. Development of appropriate modification materials and methods for metal electrode is an efficient way to improve OTFT performance, which is however a quite challenging task. In this chapter, we develop a facile strategy to modify the metal surface with graphene oxide (GO) via covalent bonds for the application in OTFT, which is not reported before. The selective covalent modification strategy is compatible with diverse patterning techniques, and the covalently linked GO-Au electrode exhibits strong robustness against solvent treatment. Remarkably, the GO-Au electrode shows very good generality with both p-type and n-type organic semiconductors, which contributes to the realization of p-/n-type OTFTs with significantly improved performance compared with the bare Au electrode. The facile and low temperature modification method, compatibility with diverse patterning techniques, robustness against solvent treatment, good generality with organic semiconductors, and high OTFT performance enable our strategy to be very promising for the application in the field of organic electronics.Secondly, we study the effect of self-assembled monolayer (SAM) on the performance of OTFT. By means of modifying different density of OTS on the silica dioxide surface in organic thin film transistors, we study the effect of different density of OTS on the performance of OTFT. The results indicate that the higher density of OTS have more beneficial effect on the performance of OTFT. The mobility of OTFT based on the highest density of OTS is 20 times to that of OTFT without modifying OTS, Indicating that the interface between organic semiconductors and dielectric layers in OTFT.In addition, we develop a modified SAM, resulting in a great increasing mobility.The roughness of octadecyltrichlorosilane (OTS) monolayer exerts great effect on the performance of organic field-effect transistors (OTFTs), but the preparation of ultrasmooth OTS monolayer is a technologically challenging task. In this chapter, a facile peeling method with PMMA is used to remove the redundant and protuberant aggregations on the OTS surface, which may serve as a post-remedy strategy to produce ultrasmooth OTS monolayer. With the facile peeling method, OTS modification can be carried out via routine experimental conditions. Atomic force microscopy (AFM) characterization confirms that these monolayers exhibit a remarkably high degree of smoothness. Organic semiconductor, Dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), deposited onto the ultrasmooth OTS monolayer has a tendency to grow in a favorable two-dimensional layered growth manner with lager grain size and less gain boundaries, which is beneficial for high charge-carrier transport. On the ultrasmooth OTS monolayer, DNTT and PDI-8CN2 OTFTs show mobilities as high as 8.16 cm2 V-1 s-1 and 0.30 cm2 V-1 s-1, which is remarkably superior to the OTFTs with pristine OTS monolayer without peeling treatment. This work resolves a common but significant puzzle about the quality of OTS modification, which would be highly meaningful for improving the performance and reproducibility of OTFT.