Theoretical Study On Charge Transport Properties In Fluorine Substituted Organic Molecular Crystals

Since highly conducting polyacetylene was discovered in the mid-1970 s by Shirakawa, Mac Diarmid and Heeger, who awarded the Nobel Prize in chemistry in 2000, π-conjugated systems have attracted much attention for its possibilities to be the next generation of electronic materials, to be exact, organic electronic materials. It is the kind of material that can be design to achieve desired property due to its structural diversity. Development of this kind material has become an active area of research, also due to the benefits of these materials such as low cost, large-area, light weight and flexibility. A great number of organic electronic materials have either been discovered or synthe-sized, and used in a variety of applications.In our work we have done a series of computational calculations of thiazole/thiophene-based oligomers with trifluoromethylphenyl, trifluoromethylated polycyclic aromatic hydrocarbons, and fluorine-substituted dibenzalacetones in order to study the relationship between charge transport and intermolecular interactions.1. With electronic band structure and density of states(DOS) calculations performed by a density functional theory(DFT) method implemented in the Vienna Ab-initio Simulation Package(VASP 5.2.12), we finally figure out that the π-π interactions have much effect on the hole transport, while intermolecular hydrogen bonding interactions are mainly responsible for the electron transport.2. The electronic band structure calculations were performed by a DFT method implemented in VASP 5.2.12, while charge transfer integrals and the reorganization energies were calculated by the ADF package and the Gaussian 09 program, respectively. By analyzing the results, we finally figure out that the π-π interactions have much effect on the hole transport, while intermolecular hydrogen bonding interactions are mainly responsible for the electron transport in the chosen systems. The reorganization energies increase along with the number of trifluoromethyl substituents increase, and dicrease as the number for benzene rings increase.3. By analyzing the electronic band structure and charge transfer integrals calculated by VASP 5.2.12 and the ADF package, respectively, we finally figure out that in contrast to the π-π interaction formed between ordinary phenyl rings for hole transport, the Fπ-π interaction was mainly responsible for electron transport in these crystals.