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Theoretical Investigations On Charge Transport Properties Of Fluorinated Aromatics

Posted on:2017-01-27Degree:MasterType:Thesis
Country:ChinaCandidate:Y HuFull Text:PDF
GTID:2271330488961520Subject:Materials Physics and Chemistry
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The organic semiconductors materials (OSCs) have many potential applications. The properties of the OSCs have vital influences to the organic device. Thus, it is important to understand the charge transport property of OSCs and design new high performance materials. In this work, we performed theorectial study on three series of OSCs by DFT method coupled with Marcus-Hush model.We selected five perfluoroarence modified oligothiophene compounds whose crystal structures were determined already and studied their HOMO/LUMO energy, hole and electron reorganization (λh and λe), ionization potential (IP), electronic affinity energy (EA), and hole and electron transfer mobilities (μh and pμe). The results show that the LUMO energy level and electron and hole reorganization energy decrease with increasing number of the thiophene rings, which is beneficial to the electron injection and air-stability enhancement. Among them, the μe of compound A5 is as high as 0.19 cm2·V-1·s-1 while the μh of A3 is 0.72 cm2·V-1·s-1. Both of them have potential application in practices.A series modified 1,3,5-tripyrrolebenzene (TPB) compounds were constructed by introducing electron-withdrawing substitution groups in specific sites to the TPB skeleton and the optimized face-to-face packing (dimer) in gas phase were predicted by DFT coupled with dispersion force correction (-D). The charge transport properties of the modified compounds were estimated on the basis of predicted dimer structures. It shows that the -CN and -F substituents can improve the EA value of this series compounds which have good air stability. The estimated μe of B1, B2 and B7 are as high as 0.433 cm2·V-1·s-1,0.198 cm2·V-1·s-1 and 0.279 cm2·V-1·s-1. At the same time, B7 shows a bipolar semiconductor behavior. B1, B2 and B7 are potential high performance OSCs.Three fluorinated 5,6,7-trithiapentacene-13-one (TTPO, C1) derivatives were designed by replacing some hydrogen atoms of TTPO with fluorine atoms. Based on the X-ray structure of TTPO, the crystal structures of the fluorinated TTPO were optimized by DFT-D in CASTEP module of Materials Studio package and the charge transport properties of TTPO and its derivatives have been investigated. Our calculations reveal that TTPO molecule has a low-lying LUMO level while its fluorinated derivatives have a further lower LUMO level and higher EA values that can increase their stability. The μe and μh of C1 are 1.01 cm2·V-1·s-1 and 0.62 cm2·V-1·s-1, respectively. The fluorinated compounds of C2 and C3 also have large values of μe (0.38 cm2·V-1·s-1 and 0.33 cm2·V-1·s-1, respectively).
Keywords/Search Tags:DFT, Charge transport, Mobility, Oligothiophene, 1,3,5-tripyrrolebenzene(TPB), 5,6,7-trithiapentacene-13-one(TTPO)
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