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STOCHASTIC APPROACH TO HOPPING TRANSPORT IN DISORDERED ORGANIC MATERIALS

E. V. Emelianova1, G. J. Adriaenssens1,*

Affiliation

  1. Semiconductor Physics Laboratory, University of Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium

Abstract

At variance with inorganic amorphous semiconductors, all electronic states in disordered organics are localized and electrical conduction can proceed by carrier hopping within the manifold of those states that are, therefore, often referred to as hopping sites. One of the most common approach to the description of charge transport in such systems is the variable-range hopping theory. While the general principles of this theory have been known and accepted for years, many important aspects and applications of this theory have only been examined more recently. In this survey we discuss a number of facets of hopping in disordered organic materials that have not received much attention in the past. Following a general outline of the calculation of the equilibrium mobility it is shown how the concept of an effective transport energy effectively reduces the description of hopping a much simpler problem of trap-controlled band transport. The influence of high carrier densities and of defect centers on the carrier mobility as well as the special case of space charge limited currents are discussed in detail. In subsequent sections, the effect of doping on the density of-states distribution and on transport characteristics are considered. The effect of polaron formation and deep trapping on the activation energy of the carrier mobility in disordered organic materials are the subject of our final section..

Keywords

Organic materials, Hopping transport, Stochastic approach.

Submitted at: Oct. 25, 2004
Accepted at: Dec. 6, 2004

Citation

E. V. Emelianova, G. J. Adriaenssens, STOCHASTIC APPROACH TO HOPPING TRANSPORT IN DISORDERED ORGANIC MATERIALS, Journal of Optoelectronics and Advanced Materials Vol. 6, Iss. 4, pp. 1105-1131 (2004)