Carrier-density and field-dependent charge-carrier mobility in organic semiconductors with correlated Gaussian disorder

• Published in: Organic electronics Vol. 10; no. 3; pp. 437 - 445
• Main Authors: Bouhassoune, M., Mensfoort, S.L.M. van, Bobbert, P.A., Coehoorn, R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2009; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Correlated disorder; Electronic transport in condensed matter; Exact sciences and technology; Gaussian disorder; Hole-only device; Hopping mobility; Physics; Poly-phenylene-vinylene; Polymers; organic compounds (including organic semiconductors); Poole-Frenkel law; Hole-only device; 72.20.Ee; Poole-Frenkel law; 73.61.Ph; Correlated disorder; Hopping mobility; Poly-phenylene-vinylene; 72.80.Le; Gaussian disorder; Phenylenevinylene polymer; Density of states; Electrical conductivity; Poole-Frenkel effect; Hopping conduction; Organic semiconductors; Carrier mobility; IV characteristic; Carrier density; Master equations; Comparative study
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2009.01.005

Recently, it has been demonstrated that for organic semiconductors with a Gaussian density of states (DOS) and with on-site energies that are spatially uncorrelated the hopping mobility of charge-carriers can be strongly carrier-density-dependent (extended Gaussian disorder model, EGDM). In the literature, it has been argued that for some materials, the on-site energies are actually spatially correlated. In this paper, we develop a full description of the mobility in a correlated Gaussian DOS (extended correlated disorder model, ECDM), using a master-equation method. We show that the mobility is less strongly carrier-density-dependent than in the EGDM, but that the field dependence is more pronounced. The field dependence is found to be described by a Poole-Frenkel factor, as has been deduced from empirical analyses of experimental data, but only in a limited field range. As an example of an application, we present a comparison between analyses of the current–voltage–temperature J( V, T) characteristics of a poly-phenylene-vinylene (PPV) based hole-only device using the EGDM and the ECDM. For both cases, excellent fits can be obtained, but with the EGDM a more realistic value of the intersite distance is found than in the case of the ECDM. We view this as an indication that site-energy correlations do not play an important role in PPV.