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Universal size-dependent conductance fluctuations in disordered organic semiconductors
A Massé1, R Coehoorn2, P A Bobbert1
1Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, Netherlands.
Physical Review Letters
|September 27, 2014
Summary
Charge transport in disordered organic semiconductors exhibits distinct behaviors based on energy disorder. Fluctuations dominate at small scales, breaking down continuum models for hopping charge transport.
Area of Science:
- Organic electronics
- Condensed matter physics
- Materials science
Background:
- Understanding charge transport in disordered organic semiconductors is crucial for device performance.
- Hopping transport is a key mechanism in these materials, influenced by energy disorder.
- Continuum models are often used but may fail at small scales.
Purpose of the Study:
- To numerically investigate charge transport in disordered organic semiconductors.
- To analyze the dependence of conductance fluctuations on region size and temperature.
- To determine the characteristic length scale where continuum descriptions break down.
Main Methods:
- Numerically exact simulations of hopping charge transport.
- Analysis of relative conductance fluctuations for uncorrelated and dipole-correlated Gaussian energy disorder.
- Scaling analysis of data with a characteristic length dependent on temperature.
Main Results:
- Universal power-law dependence of fluctuations on region size for uncorrelated disorder.
- Non-power-law dependence for dipole-correlated disorder.
- A characteristic length, temperature-dependent, governs data collapse, reaching up to 100 nm for correlated disorder.
- Fluctuations dominate below this characteristic length, invalidating continuum models.
Conclusions:
- Continuum models are insufficient for describing charge transport in disordered organic semiconductors at small length scales.
- The nature of energy disorder (uncorrelated vs. correlated) significantly impacts charge transport behavior.
- A characteristic length scale, influenced by temperature and disorder correlation, defines the transition from fluctuating to continuum-like transport regimes.
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