Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 19, Issue 17, Pages 10854-10862Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c6cp06436a
Keywords
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Funding
- Xerox Foundation/Xerox Research Centre of Canada (XRCC)
- DAAD
- UK Engineering and Physical Sciences Research Council [EP/K029843/1, EP/K030671/1, EP/M025020/1]
- Royal Society
- BMBF grant MEDOS [FKZ 03EK3503B]
- BMBF grant MESOMERIE [FKZ 13N10723]
- BMBF grant InterPhase [FKZ 13N13661]
- [646259]
- [NMP-20-2014]
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We present a multi-scale model for charge transport across grain boundaries in molecular electronic materials that incorporates packing disorder, electrostatic and polarisation effects. We choose quasi two-dimensional films of tri-isopropylsilylethynyl pentacene (TIPS-P) as a model system representative of technologically relevant crystalline organic semiconductors. We use atomistic molecular dynamics, with a force-field specific for TIPS-P, to generate and equilibrate polycrystalline two-dimensional thin films. The energy landscape is obtained by calculating contributions from electrostatic interactions and polarization. The variation in these contributions leads to energetic barriers between grains. Subsequently, charge transport is simulated using a kinetic Monte-Carlo algorithm. Two-grain systems with varied mutual orientation are studied. We find relatively little effect of long grain boundaries due to the presence of low impedance pathways. However, effects could be more pronounced for systems with limited inter-grain contact areas. Furthermore, we present a lattice model to generalize the model for small molecular systems. In the general case, depending on molecular architecture and packing, grain boundaries can result in interfacial energy barriers, traps or a combination of both with qualitatively different effects on charge transport.
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