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Charge transport in amorphous organic semiconductors

Abstract

Organic semiconductors with the unique combination of electronic and mechanical properties may offer cost-effective ways of realizing many electronic applications, e. g. large-area flexible displays, printed integrated circuits and plastic solar cells. In order to facilitate the rational compound design of organic semiconductors, it is essential to understand relevant physical properties e. g. charge transport. This, however, is not straightforward, since physical models operating on different time and length scales need to be combined. First, the material morphology has to be known at an atomistic scale. For this atomistic molecular dynamics simulations can be employed, provided that an atomistic force field is available. Otherwise it has to be developed based on the existing force fields and first principle calculations. However, atomistic simulations are typically limited to the nanometer length- and nanosecond time-scales. To overcome these limitations, systematic coarse-graining techniques can be used. In the first part of this thesis, it is demonstrated how a force field can be parameterized for a typical organic molecule. Then different coarse-graining approaches are introduced together with the analysis of their advantages and problems. When atomistic morphology is available, charge transport can be studied by combining the high-temperature Marcus theory with kinetic Monte Carlo simulations.  More>>
Publication Date:
Mar 15, 2011
Product Type:
Thesis/Dissertation
Report Number:
ETDE-DE-2540
Resource Relation:
Other Information: TH: Diss. (Dr.rer.nat.)
Subject:
36 MATERIALS SCIENCE; ALUMINIUM COMPOUNDS; AMORPHOUS STATE; CARRIER MOBILITY; CHARGE TRANSPORT; COMPUTERIZED SIMULATION; ELECTRIC FIELDS; EXTRAPOLATION; HOLES; KINETICS; MONTE CARLO METHOD; MORPHOLOGY; ORGANIC SEMICONDUCTORS; ORGANOMETALLIC COMPOUNDS; QUINOLINES
OSTI ID:
21485511
Research Organizations:
Mainz Univ. (Germany). Fachbereich 18 - Physik
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
TRN: DE11GB464
Availability:
Commercial reproduction prohibited; OSTI as DE21485511
Submitting Site:
DE
Size:
140 pages
Announcement Date:
Oct 27, 2011

Citation Formats

Lukyanov, Alexander. Charge transport in amorphous organic semiconductors. Germany: N. p., 2011. Web.
Lukyanov, Alexander. Charge transport in amorphous organic semiconductors. Germany.
Lukyanov, Alexander. 2011. "Charge transport in amorphous organic semiconductors." Germany.
@misc{etde_21485511,
title = {Charge transport in amorphous organic semiconductors}
author = {Lukyanov, Alexander}
abstractNote = {Organic semiconductors with the unique combination of electronic and mechanical properties may offer cost-effective ways of realizing many electronic applications, e. g. large-area flexible displays, printed integrated circuits and plastic solar cells. In order to facilitate the rational compound design of organic semiconductors, it is essential to understand relevant physical properties e. g. charge transport. This, however, is not straightforward, since physical models operating on different time and length scales need to be combined. First, the material morphology has to be known at an atomistic scale. For this atomistic molecular dynamics simulations can be employed, provided that an atomistic force field is available. Otherwise it has to be developed based on the existing force fields and first principle calculations. However, atomistic simulations are typically limited to the nanometer length- and nanosecond time-scales. To overcome these limitations, systematic coarse-graining techniques can be used. In the first part of this thesis, it is demonstrated how a force field can be parameterized for a typical organic molecule. Then different coarse-graining approaches are introduced together with the analysis of their advantages and problems. When atomistic morphology is available, charge transport can be studied by combining the high-temperature Marcus theory with kinetic Monte Carlo simulations. The approach is applied to the hole transport in amorphous films of tris(8- hydroxyquinoline)aluminium (Alq{sub 3}). First the influence of the force field parameters and the corresponding morphological changes on charge transport is studied. It is shown that the energetic disorder plays an important role for amorphous Alq{sub 3}, defining charge carrier dynamics. Its spatial correlations govern the Poole-Frenkel behavior of the charge carrier mobility. It is found that hole transport is dispersive for system sizes accessible to simulations, meaning that calculated mobilities depend strongly on the system size. A method for extrapolating calculated mobilities to the infinite system size is proposed, allowing direct comparison of simulation results and time-of-flight experiments. The extracted value of the nondispersive hole mobility and its electric field dependence for amorphous Alq{sub 3} agree well with the experimental results. (orig.)}
place = {Germany}
year = {2011}
month = {Mar}
}