Phonon-assisted tunnelling as a process determining current dependence on field and temperature in MEH-PPV diodes

In this paper we would like to show the applicability of phonon-assisted tunnelling theories for explanation of temperature-dependent current-voltage (I-V) characteristics of diodes based on organic thin films of conjugated polymers, such as poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). For this purpose the I-V characteristics measured for MEH-PPV by Campbell et al (1997 J. Appl. Phys. 82 6326), Lupton and Samuel (1999 J. Phys. D: Appl. Phys. 32 2973), and van Woudenbergh et al (2001 Appl. Phys. Lett. 79 1697) are compared with the free carrier generation rate dependence on field strength using the phonon-assisted tunnelling theories. A strong dependence of charge carrier mobility on temperature is also explained by this model. The presented model allows us not only to explain the temperature variation of I-V and mobility data, but also to estimate the density of traps taking part in the current flow.