Theoretical Studies On The Charge Transport Performances Of Organic Materials: Impact Of Fluorione

Since the※rst report of organic thin-film field-effect transistor (OTFT) materials byTsumura in1986, signi※cant progress has been achieved. Compared to conventional inorganiccounterparts, OTFT has attracted considerable attention, due to the straightforward chemicalmodification, commercial availability, and low cost. Organic semiconductor material still hasa few demerits, such as the complexities of molecular structures, difficulty with of controllingintermolecular interactions, varieties of molecular packings and so on, which bring manychallenges to experimental and theoretical.In this article, we combined density functional theory (DFT) with Marcus theory to probethe complicated relations between the molecular chemistry structure and transport property indepth, probe into the transport mechanism. We hope we can give a hand to scientists indesigning and developing high-performance organic transport materials. Our work mainlyincludes two aspects as follows.Oligothiophene derivatives, as one of typical organic carrier transport materials, havereceived widespread attention. The influence of the chain length of thiophene, variation of thesubstituents and the fluorination were investigated in detial by combining Marcus formalismat the level of density functional theory (DFT), focusing on geometries and frontier molecularorbitals, intramolecular reorganization energy, intermolecular electronic coupling and carriermobility. The results show that the charge carrier mobility increases with the thiophene chainlength.1D has the best charge carrier transport properties which is attrbuted to its betterface-to-face π-stacked structure. The fluorination may be helpful in improving of the stabilityand carrier transport ability.Many factors have been discussed with DFT method to explore the difference in holecharge-carrier mobilities between PPT and FPPT. We find that the the incorporation offluorine increases the transfer integrals and mobilities by densifying π-stacking and enrichingintermolecular interactions. The C-H…F, F…F and C…F intermolecular interactions, whichwill be helpful in forming effective charge carrier transporting network. We design newfluorinated compound FPPT’ and predict its crystal packing motif. The charge mobility ofFPPT’(2.49cm2/V·s) is one-fold higher than PPT’(1.07cm2/V·s), which furtherdemonstrates that fluorination may be an effective method to improve the carrier carriermobility.