Sexithiophene doping

Analysis of the spin-1/2 2-PADMR spectrum is more complicated as it contains two features with increased and decreased transmission. As the photoexcitation density is proportional to -AT, we describe these as PA-quenching (Sn<0) and PA-enhancing (Sn >0) bands. We defer detailed discussion of the spectrum to the following section, where we compare the doping, PA, and PADMR studies of a-sexithiophene (u-6T) and polythiophene. Magnetic resonance is found to enhance... 

Loiacono MJ, Granstrom EL, Frisbie CD (1998) Investigation of charge transport in thin, doped sexithiophene crystals by conducting probe atomic force microscopy. J Phys Chem B 102 1679-1688... 

The theory predicts a strong dependence of photogeneration efficiencies on the field and it approaches unity at high field. The temperature sensitivity decreases with the increase in field. The theory has found satisfactory explanations in the photogeneration process in many organic disordered systems, such as PVK (Scheme la) [25], and triphenylamine doped in polycarbonate [26], Figure 4 shows an example of the field dependence of c() calculated from Eq. (22) (the solid lines) to fit the quantum efficiency data at room temperature for hole and electron generation in an amorphous material. The material consists of a sexithiophene covalently linked with a methine dye molecule (compound 1) (Scheme 2). 

C. Kendrick and S. Semancik, Doping effects and reversibility studies on gas-exposed alpha-sexithiophene thin films , Journal of Vacuum Science Technology A 16, 3068 (1998). 

The signal travels through a thick, or even molecularly thin, semiconductor that connects these electrodes it could be an inorganic semiconductor (doped Si, doped Ge), an organic conducting polymer (polyaniline, polythiophene, polyacetylene), a carbon nanotube, or an organic semiconductor (sexithiophene). 

FIGURE 4.3.23 Scheme of the CP-AIM experiment in which an An-coated AFM tip (A) is used to make electrical contact to crystal layers of sexithiophene (6T) grown by vapor deposition on Si02/Si. (B) A microfabricated An wire serves as a drain electrode. (C) Highly doped Si substrate is a gate. (From Kelley, T.W. and Frisbie, C.D., J. Phys. Chem. B 105, 4538-4540, 2001. With kind permission.)... 

HREELS spectra of Na-doped sexithiophene [239] reveal a broad unstructured loss band at 1.1 eV with possible maxima at 1.3 eV and 1.8 eV depending on the doping level. Another new peak is located at 1.0 eV and the intensity of the 0.75 eV emission is enhanced. AH... 

In poly(5-vinyl-2,2 5, 2"-terthiophene), in which terthiophene is a side group of a carbon-carbon chain polymer, the terthiophene side chains cross-link when the polymer is doped with FeCls or SbCls in solution or as thin film. The terthiophene radical cations, initially generated upon doping, couple with neighboring neutral species to yield the radical cations of sexithiophene. The dedoping of the polymer with triethylamine yields an insoluble, cross-linked material [242]. 

At a concentration of 1.3 Na/a-6T HREELS spectra of Na-doped sexithiophene [318] reveal a new, very broad loss-structure at 1.7 eV (Fig. 46) (for bare sexithiophene compare also Fig. 38). With further Na-deposition the intensity of this loss peak increases very strongly and dominates the spectrum at the highest concentration of 8.3 Na/a-6T. Simultaneously a loss peak at 3.9 eV arises. Both effects lead to a less clear peak structure at energies between 1.0 and 4.5 eV due to the broadness of the peaks. Depending on the Na concentration there may also maxima be detected at 1.3 and 2.1 eV which arise within the 1.7eV peak structure as shoulders. There may also be a new peak at 0.95 eV for 3.2 Na/a-6T accompanied by a slight increase of the peak intensity at 0.75 eV. This intensity increase can only be explained by an additional electronic energy loss at 0.75 eV because the intensity of the overtone of the C—H stretch vibration is constant. The new peaks can either be explained as... 

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