Homogeneous Charge Transport

Three processes can control the rate of homogeneous charge transport through a redox-active polymer film, i.e. electron self-exchange between redox-active centers,... 

Tables 5.4 and 5.5 provides the homogeneous charge transport diffusion coefficients, Dct, for osmium polymers with different loadings in HCIO4 and H2SO4. Further information about the nature of these processes can be obtained by determining the thermodynamic parameters. These parameters are also summarized...

Experimental Results and Discussion 3.2.1. Homogeneous Charge Transport... 

The good EL performance of these devices results from the combination of the emission properties of the main chain (blue side) and the Ir(III) units (red side) and from modulation of the charge transport process by the incorporated carbazole units. These features are associated to a homogeneous single-layer material, which represents an advantage against using blends and multilayer structures that can be subject to phase separation. 

For dielectrics, the choice of solvent is also essential for a satisfying film morphology. The film should be homogeneous, without pinholes, and should have a smooth and defined surface. The interfaee between the dieleetrie and the semiconductor is very important, since that is where charge transport takes place in a FET. Defects should be kept at a minimum, since defects are trap sites and traps induce hysteresis, a difference in device current between a forward and a backward voltage sweep. This hysteresis can be taken advantage of in a memory device, but for FETs it should be as low as possible. 

Electric charge transport across such interface is less efficient than in the case of homogeneous metal/pentacene interface. This is reflected by more than one order of magnitude lower effective field-effect mobility, observed in the samples fabricated by the growth rate of 0.05 nm/min (Fig. 1(a), bottommost curve). The existence of plateau in mobility vs. thickness curve (Fig. 1(b)) is likely to be a consequence of gradual closing of the uncovered region near the metallic contacts. 

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