Transport in Organic Materials

Although it has not yet been possible to fully analyse the temperature behaviour and, in particular, to determine the mobility from the device characteristics of this ideal OSC-device, we believe that such model devices, where structural defects such as domain boundaries and reorientation layers as well as contamination are largely absent will be very important for unravelling the physics governing charge transport in organic materials. 

In the last few years the first theoretical models describing spin injection at hybrid organic-inorganic interfaces and spin transport in organic materials were proposed. Most models take into account the polaronic nature of carriers in organic semiconductors [17, 18]. The interface role was strongly underlined by, among others. Smith and coworkers [19]. 

This low density of surface defects is the major factor that determines the record performance of single-crystal OFETs and enables exploration of the fundamental limits of charge carrier transport in organic materials, hi addition, these devices provide an efficient tool for studying the polaron-defect interactions. This section focuses on defects that can be formed in the process of crystal growth, OFET fabrication, and as a result of the interaction with ambient environment. 

For route 2, charge transport mechanism is similar to the hopping mechanism of small molecules. According to the charge transport theory developed hy Bredas et al. [22], the charge carrier transport in organic materials can be described by Marcus electron transfer theory (Eq. 1.3). In organic ciystals, the AG is 0 because the electron transfer happens in a same kind of molecules. Thus the Eq. 1.3 formula can be simplified into Eq. 1.4 as follows ... 

The important topic of charge transport in organic materials is outside the scope of this chapter, and for that we refer the reader to excellent review papers and book chapters [7-11]. Suffice here to recall a few basic concepts that will help in dealing with the problem of interfaces. 

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