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Charge mobility of perfluoroarence modified oligothiophene crystals

YONG HU1, JUN YIN1, XUE-HAI JU1,*

Affiliation

  1. Key Laboratory of Soft Chemistry and Functional Materials of MOE, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China

Abstract

Density functional theory (DFT) was employed to calculate the property of some single-crystal organic semiconductors. The oligothiophene derivatives from 1 to 5 were studied from the aspects of frontier molecular orbital energy (HOMO, LUMO), bandgap (Eg), ionization energy (IE) and electron affinity (EA), reorganization energy (λ), hopping distance (ri) and overlap integral (H) during the hole and electron transfer process. The charge mobility was calculated by Marcus theory and Einstein relation. As the number or thiophene conjugate ring increase, the energy level of LUMO, the bandgap and reorganization energy (λ) have a trend of decrease. And the longer the main chain, the better the coplanarity. At the same time, the IE and EA have an opposite trend, the IE increasing while EA decreasing. These indicate that increasing the π-conjugate ring can make it easier of both electron and hole injection. The phene ring overlap and the interaction between adjacent molecules have a great influence on the charge transfer integral (H) which is essential for large charge mobility value. These series of oligothiophene compounds turn their nature from p-type to n-type by introducing perfluoroarence rings to the parent molecule, and the electron mobility (μ−) of compound 5 is 0.19 cm2·V−1·s−1, which is large enough to meet the requirement of a n-type organic semiconductor..

Keywords

DFT; Charge mobility; Marcus theory; Organic semiconductor; Oligothiophene.

Submitted at: April 15, 2015
Accepted at: Sept. 9, 2015

Citation

YONG HU, JUN YIN, XUE-HAI JU, Charge mobility of perfluoroarence modified oligothiophene crystals, Journal of Optoelectronics and Advanced Materials Vol. 17, Iss. 9-10, pp. 1555-1562 (2015)