Fabrication And Performance Investigation Of Organic Single Crystal Field-effect Transistors

Organic semiconductors (OSCs) have attracted considerable attentions due to their advantages of solution-processable, flexible, low-cost, large-area fabrication and their potential in integrated circuits. As one of the most representative utilizations, organic field-effect transistors (OFETs) have been remarkably developed over the past decades. Currently, the performance of OFETs has improved immensely, with FET mobility in some case exceeding those of amorphous silicon FETs. In contrast, the overall development of n-type and ambipolar OSCs still lags behind their p-type counterparts in terms of mobility, ambient stability, the number of semiconductors, and so on. Tuning the energy level by introducing keto-carbonyl groups, dicyano methylene groups to the backbone of s-indaceno[1,2-b:5,6-b’]dithiophene, our group synthesized a series of n-type and ambipolar semiconductors based on s-indaceno[1,2-b:5,6-b’]dithiophene derivatives and investigated it’s thin film transistors performance.In this thesis, in order to explore the intrinsic properties of these materials, investigate the relationship of between structure and performance, fabricate high performance devices, we have further investigated single crystal OFETs based on these n-type and ambipolar derivatives of s-indaceno[1,2-b:5,6-b’]dithiophene, and analyzed the relationship between structure and performance, this will provide a guideline for further molecular design and synthesis.The main results are as follows:1. A preliminary investigation have been carried out on the preparation of single crystal OFETs: First:self-assembled monolayer of octadecyltrimethoxysilane (OTMS) was deposited on Si/SiO2substrate by solution phase; the surface was very flat with a root-mean-square roughness of0.23nm. Then FETs were fabricated with pentacene as active layers, FET devices showed high hole mobility up to3.6cm2V-1s-1; Second:we had a preliminary investigation on the preparation of organic single crystal.2. Single crystals of C2-CN and C12-CN were prepared by physical vapor transport technique, and fabricated single crystal FETs with Au as source/drain electrodes. Devices showed high electron charge transport behavior both in air and in N2, the highest electron motilities obtained in N2was1.3cm2V"1s’1and in air was0.53cm2V-1s-1for C2-CN.3. We have fabricated the single crystals of dicyano methylene groups substituted s-indaceno[1,2-b:5,6-b’]dithiophene by drop-casting, and characterized by XRD, TEM, etc. and combined it’s single crystal structure to analysis the molecular packing of single crystal, the result showed that the molecular arrangements in the single crystals were1D π-stacking. Single crystal FETs were fabricated based on the single crystals of C-DQ, the devices exhibited typical ambipolar charge transport behavior. Among these materials, the electron and hole mobilities of0.12and0.06were observed for the single crystal OFETs of C2-DQ, respectively.