Dopant independent

Figure 13.30. (a) UPS He 11 spectra of iindo ed a6T. pure FeClj. and two differently doped a6T films. The percentages refer to the reaction a6T + 12 FeCl, -> a6T + 6 FeCl +6 FeClj, i.e. 100% correlates with one charge and radical per thiophene ring to allow for comparison with polymer data. The vertical dotted lines indicate the positions of the lower tr-band which was used as stable, i.e. dopant independent, reference to determine peak shifts, (b) UPS He I spectra of undoped a6T and for a6T with increasing doping levels. The spectra were calibrated as indicated in (a). Also indicated is the Fermi level Ep as determined from a clean Au foil [119). 

Druy et al. [29] reported that the kinetic studies on d.c. electrical conductivity decay of p-type doped Shirakawa polyacetylene in an inert atmosphere and indicated that two types, namley dopant dependent and dopant independent reactions, are involved in the degradation process of polyacetylene. It was observed... 

Trilayer structures offer the additional possibility of selecting the emissive material, independent of its transport properties. In the case of small molecules, the emitter is typically added as a dopant in either the HTL or the ETL, near the interface between them, and preferably on the side where recombination occurs (see Fig. 13-1 c). The dopant is selected to have an cxciton energy less than that of its host, and a high luminescent yield. Its concentration is optimized to ensure exciton capture, while minimizing concentration quenching. As before, the details of recombination and emission depend on the energetics of all the materials. The dopant may act as an electron or hole trap, or both, in its host. Titus, for example, an electron trap in the ETL will capture and hold an election until a hole is injected nearby from the HTL. In this case, the dopant is the recombination mmo.-... 

The interest of physicists in the conducting polymers, their properties and applications, has been focused on dry materials 93-94 Most of the discussions center on the conductivity of the polymers and the nature of the carriers. The current knowledge is not clear because the conducting polymers exhibit a number of metallic properties, i.e., temperature-independent behavior of a linear relation between thermopower and temperature, and a free carrier absorption typical of a metal. Nevertheless, the conductivity of these specimens is quite low (about 1 S cm"1), and increases when the temperature rises, as in semiconductors. However, polymers are not semiconductors because in inorganic semiconductors, the dopant substitutes for the host atomic sites. In conducting polymers, the dopants are not substitutional, they are part of a nonstoichiometric compound, the composition of which changes from zero up to 40-50% in... 

Using this method, homogeneous alloys, segregated alloys, layered bi-metallics, and decorated particles are all readily accessible. An obvious advantage of the precursor concept over the conventional salt-impregnation method is that both the size and the composition of the colloidal metal precursors may be tailored independent of the support. Further, the metal particle surface may be modified by lipophilic or hydrophilic protective shells and coated by intermediate layers, e.g., of oxide. The modification of the precursor by dopants is also possible. 

In many ceramics, intrinsic and extrinsic disorder, as well as the disorder due to nonstoichiometry, have to be considered. Independent of the dopant level, the mass action laws of intrinsic disorder, of the e-h equilibrium and of the reaction with the surrounding phase are valid in thermodynamic equilibrium. Together with the electroneutrality equation... 

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