A Theoretical Study of the Molecular Organization Behavior and the Charge Transfer Mechanisms of Poly-3-hexylthiophene
Date Issued
2009
Date
2009
Author(s)
Lan, Yi-kang
Abstract
The regioregular poly-3-hexylthiophene (rr-P3HT) system can reach mobility as high as 0.1 cm2/Vsec all around the polymer based organic field effect transistors (OFETs). Thus, to clarify the factors that affect the charge mobility and the transport mechanisms of the P3HT based OFET systems are of great importance. We use quantum mechanical (QM) methods to interpret the charge mobility and the transport properties of the P3HT molecules along the intrachain and interchain directions. Our approach is illustrated by a hopping transport model, in which we examine the variation of the charge mobility with the torsional angle and the inter-molecular distance between two adjacent thiophene segments. We also simulate the packed and vacuum state P3HT structures via the molecular dynamics (MD) simulations to obtain the detail chain conformation. he QM and MD results indicate that the main charge transfer route within the P3HT ordered domains is along the intrachains instead of the interchains. The calculation results of the interchain hole mobility is around 10-2 cm2/Vs, which is consistent with the excremental data from the P3HT single fibril. Besides, we proposed a crossing-point/bridging-chain model to illustrate the chain conformation in the disordered regions. This model can explain the mobility evolutions as a function of Mw/nanofibril-width very well. Finally, the average charge mobility approximation suggested that the disordered region is the mobility limitation zone of the whole systems since the large difference of mobility between the ordered and disordered state. One should consider the contributions of the disordered region in improving the total charge mobility in the OFETs system.
Subjects
Charge Transfer
Charge mobility
Transfer Integral
P3HT
OFETs
Type
thesis
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