Study On The Charge Transfer Mobility Of Organic Semiconductor By Density Functional Theory

The organic semiconductor is an organic material with semiconductor property, which conductive property is between the metal and the insulator. Compared with the traditional semiconductor materials, organic semiconductor materials have many advantages, such as: flexible, easy for processing, low cost, large-area applications. Because there are so many advantages of organic semiconductor, in recent years, much more attention has been paid in organic semiconductor materials.The organic semiconductor is molecular crystal, whoes minimum constituent unit is an organic molecule. In order to obtain better performance organic semiconductor, we can modify the organic molecule (such as adding or reducing the group on the organic molecules). An important parameter to measure the performance of the organic semiconductor material is the charge mobility.This work investigates the relationship between the charge transfer mobility (μφ) of organic semiconductor material Benzothieno-Benzothiophene (BTBT) and micro physical parameters associated with charge transfer, such as electronic coupling between molecules (charge transfer integrals), intra-molecular coupling vibration (the reorganization energy) and stacking structural parameters of molecules in the organic semiconductor material by theoretical method based on density functional theory (DFT) and Marcus-Hush theory using Gaussian and ADF software package. The anisotropic function of charge transfer mobility is also derived, which could be used to predict the extreme value and its direction of the mobility and design novel organic semiconductor material with high performance based on BTBT. In this work, we investigated the charge transfer mobility of the derivatives from BTBT, such as C8-BTBT, C10-BTBT and C12-BTBT. The hole-transport mobility (μhole) of these crystals is indicated to be much larger than their electron-transport mobility (μelectron), which means they are p-type semiconductor. As the carbon chain is lengthened from8to12carbon atoms, the mobilities of C8-BTBT, C10-BTBT and C12-BTBT are also increased. The raised charge mobility is ascribed to the decrease of the angle θT1and the rise of the face-to-face area for the P and T1dimer. In other words, the crystal structure of them is packed more tightly, which are induced by the lengthening of the side carbon chain. This simple model might pave novel way for designing better functional organic semiconductors via modification of the side chain to increase the charge mobility.This work also investigates on the catalytic mechanism of a novel catalyst for carbon dioxide capture and conversion by DFT and transition state (TS) theory. As we all know, carbon dioxide is the most abundant and cheap C1resource, which is nontoxic, nonflammable, and renewable, however, it’s also one of the main greenhouse gases. Based on these characteristics, the chemistry of carbon dioxide has attracted much attention from the whole world. Recently, it is the main strategy to realize efficient carbon dioxide capture and conversion via chemical technologies. We used quantum calculations to investigate the possible mechanism. All calculations were performed with DFT using the Gaussian09software package. The reaction is demonstrated to be occurred easily by the calculated low activation energy of each intermediate reaction.