Charge transport metal-organic interfaces

Charge Transport across Metal-Organic Interfaces.142... 

This offset is in turn a good estimate of the potential barrier to hole injection from the metal to the semiconductor. As shown in Figure 2.4.2(b), applying a positive bias to the metal relative to the semiconductor can result in hole injection (so-called thermionic emission) into the valence band if the holes can surmount the barrier Ep -EyA similar discussion holds for electron injection into the conduction band, but in that case the metal is biased negative and the barrier is determined by Ec - Ep. Thus, the electronic strnctnre of metal-organic semicondnctor interfaces plays a crucial role in determining the charge transport characteristics of the contact. 

Organic semiconductors are used in many active devices. Many can be processed in solution and can therefore be printed. The charge transport properties largely depend on the deposition conditions, which are influenced by the nse of solvents, the deposition technique, concentration, interfaces and so on. Most of the organic semiconductors used today are p-type (e.g., pentacene and polythiophene), but the first n-type materials have also become available and these mean that complementary metal-oxide-semiconductor (CMOS) circuits can now be fabricated. 

The function of neutral carriers, such as the crown ether compounds discussed above, is to bind ions reversibly and to transport them across the aqueous/organic interface. The neutral carrier forms a solvation shell around a cation of appropriate charge and size, thereby solubilizing it in the organic phase. Some influencing factors are important, such as, steric interaction and the effect of the solvent on the metal cations (125). Ideally, these induce a selective permeation of one type... 

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