Revisiting the Concept of Carrier Heating in Hopping Transport

Description

Charges can be viewed to migrate through amorphous materials like
disordered organic semiconductors due to hopping between localised
states. This motion is governed by a complex interplay of energetic
disorder, electric field, interactions, temperature and other parame-
ters. The concept of carrier heating holds the promise of being able to
conveniently predict field-dependent steady state charge carrier den-
sities (SSCCD).[1] The SSCCD can be described with a Fermi Dirac
distribution such that the impact of an electric field manifests in an
effective temperature; provided that electric field and interactions are
weak enough. As the conditions for the validity of this concept are still
debated [2], we provide here the exact analytical SSCCD for arbitrary
field strengths and low charge carrier densities. We demonstrate that
the carrier heating effect originates from a modification of the ener-
getic disorder rather than from an effective temperature. By virtue of
numerical Kinetic Monte Carlo simulations, the limits of the effective
temperature approximation and the field dependence of the effective
temperature are revealed.
[1] B. I. Shklovskii et al. in Transport, Correlation and Structural
Defects, by H. Fritzsche, World Scientific, Singapore (1990), p. 161
[2] S. D. Baranovskii, Phys. Status Solidi B, 251, 487-525 (2014)

Period	23 Mar 2017
Held at	DPG Spring Meeting
Event type	Conference
Location	Dresden, Germany
Degree of Recognition	International