Theoretical Study Of Electronie Properties Of Organic Devices And Functionalized Graphene

We combined with experiments and used the first-principle method to investigate the electric properties of organic semiconductor device and functionalized graphene. The study is concentrated on the relationship between charge transport properties of organic semiconductor and varieties of internal and external factors, such as its packing style; we studied the chemical doped graphene, our results reveals that doped graphene has a3N rule similar to the related rule in carbon nanotubes and graphene nanoribbons; and studied the physical and chemical functionalized graphene. The main contents of the thesis are as follows:1. Based on the previous works, we proposed a new method to calculate charge carriers mobility of organic thin film. Using this method, we evaluated the mobilities of pentacene, tetracene and rubrene. Simulational results agree very well with experiments. At the same time, we discussed the dependence of the basis sets to mobility in this method, result implies that small basis sets can achieve a reliable mobility as the big basis sets can do, which can reduce computational load largely.2. In order to determine the difference and the quality of various mobility simulation methods, we employ these methods to investigate charge transport of Cn-BTBT molecules. In this paper, we discussed the effects of various mechanisms to the charge transport, and pointed out the limitation of Marcus theory and the unneglectable influence of thermal fluctuation.3. Using the thin film mobility simulation method, we investigated the charge transport properties of series N-Heteropentacenes and its derivatives. Simulation results show that the electron mobility of this molecule will increase, while the hole mobility decrease, as the N elements increase in the molecule. This tendency agrees with the experiments. More detail analyses indicated that the transport capability of hole and electron are mainly depended on the interface injection barriers between the organic materials and the electrode.4. We studied the effect of intermolecular packing structure to charge transport properties in the device of a series of s-indaceno [1,2-b:5,6-b’] dithiophene-4,9-dione derivatives. We get a conclusion that different devices of the similar molecule with the same conjugated structure could have different mobility in theory for the first, which is the same with experiments.5. We employing the first-principle methods investigate the electronic properties of N, B. S. Al, P or Si doped graphenes. It revealed that the doped graphene could show an interesting physical regularity, which can be described by a simple3N rule:a doped graphene has a zero or zero closing gap at the Dirac point when its primitive cell is3N×3N (N is an integer), otherwise there is a gap tunable by the dopant concentration.6. To open the graphene zero band gap, we need to change the graphene structure. CN polymer is the one of the member. We investigated varieties of graphene-like CN polymer materials, and reveal that different CN polymers show different electronic properties which is controllable by synthesis method. These different CN polymers can be used to construct heterojunction for photocatalysis.7. We studied the effect of CH3NH2molecule absorbed on graphene surface to graphene Workfunction, Fermi energy level and band gap. Our results show that physical modification of graphene can bring about small change to graphene.8. We combined with experiments and studied the photo-response of series of chemical modified graphene. Computational results show that different molecule modified graphene have a similar band structure, it means that their photo-response should have similar wave length dependence. Further analyses points out that: different modified graphene holds different ability to absorb and desorb O2, which brings about different photo-responses.