Charge-transfer peak

In order to include a wider range of solvents than those in which any of the Y values can be conveniently measured, other attempts have been made at correlating solvent polarities.395 Kosower found that the position of the charge-transfer peak (see p. 79) in the uv spectrum of the complex (87) between iodide ion and 1-methyl- or l-ethyl-4-carbometh-... 

The ultraviolet/visible spectra of the polymers provide no surprises. The stronger ultraviolet peak is quite solvent dependent, which is consistent with its assignment as a charge-transfer peak. 

Sandberg et al. examined the effect of light on the FeCls-doped poly(3-nonylthiophene) [161]. The charge transfer bands of the FeCU" anion occurred at 241, 314 and 367 nm. Irradiation of the doped polymer at 367 nm or lower wavelengths resulted in an emergence of the interband transition peak at 480 nm and decreased absorption peaks due to the charge transfer peaks of FeCl4 and the bipolaron bands. The effect of... 

For quasi-reversible systems (with 10 1 > k" > 10 5 cm s1) the current is controlled by both the charge transfer and mass transport. The shape of the cyclic voltammogram is a function of k°/ JnaD (where a = nFv/RT). As k"/s/naD increases, the process approaches the reversible case. For small values of k°/+JnaD (i.e., at very fast i>) the system exhibits an irreversible behavior. Overall, the voltaimnograms of a quasi-reversible system are more drawn-out and exhibit a larger separation in peak potentials compared to those of a reversible system (Figure 2-5, curve B). 

Figure 13. Numerically calculated PMC potential curves from transport equations (14)—(17) without simplifications for different interfacial reaction rate constants for minority carriers (holes in n-type semiconductor) (a) PMC peak in depletion region. Bulk lifetime 10" s, combined interfacial rate constants (sr = sr + kr) inserted in drawing. Dark points, calculation from analytical formula (18). (b) PMC peak in accumulation region. Bulk lifetime 10 5s. The combined interfacial charge-transfer and recombination rate ranges from 10 (1), 100 (2), 103 (3), 3 x 103 (4), 104 (5), 3 x 104 (6) to 106 (7) cm s"1. The flatband potential is indicated.

Figure 16 shows such PMC peaks in the depletion region for electrodes of Si,9 WSez8 and ZnO.12 They all appear near the onset of anodic photocurrents. They have different shapes, which, however, can easily be explained with the assumption of potential-dependent interfacial charge-transfer and charge recombination rates. 

Experimental evidence with very different semiconductors has shown that at semiconductor interfaces where limited surface recombination and a modest interfacial charge-transfer rate for charge carriers generate a peak... 

The conspicuous separation between the cathodic and anodic peak potentials was initially interpreted in terms of the simple theory for redox polymers as a kinetic effect of slow heterogeneous charge transfer the thermodynamic redox potential of the whole systems was calculated from the mean value between Ep and Ep ... 

---