Electron mobility mixtures

Figure 8 The field dependencies of electron mobilities for a mixture of DPQ in PS and PC.

Figure 9 The temperature dependence of the zero-field electron mobility for a mixture ofDPQandPS.

Electron mobilities in polymers were first described by Gill (1972). The materials studied by Gill were mixtures of TNF and PVK. These form a three-component system containing free TNF, TNF PVK charge-transfer units, and free PVK (Weiser, 1972). In TNF and the charge-transfer units, electron transport dominates, whereas in PVK only hole transport is observed. The mobilities were in the range of 10-9 to 10-6 cm2/Vs for fields of 5.0 x 105 V/cm. To describe the field and temperature dependencies, Gill introduced the expressions... 

Figure 15 The field dependencies of the electron mobilities of mixtures of TNF and PVK.

TNF dispersed in the polyester. Figure 19 shows a plot of log(p/p2) versus p for TNF doped polyester. From the slope, the wavefunction decay constant was determined as 1.8 A, the same as for electron transport in TNF.PVK mixtures. In comparing the results for the TNF dispersions and TNF PVK mixtures, Gill concluded that complexing TNF with PVK did not affect electron transport through the TNF sites. In agreement with Gill s results, Emerald and Mort (1974) later reported an electron mobility of 6.0 x 10-5 cm2/Vs for TNF at 4.0 x 105 V/cm. 

Seki (1974) measured electron mobilities in TNF and PVK mixtures. The mobilities were in the range of 10-9 to 10-6 cm2/Vs and strongly field dependent. A key feature of Seki s results is the superimposition of current transients, when normalized to the transit time, for transit times varying by over two orders of magnitude. This is described as universality and a fundamental prediction of the Scher-Montroll (1975) formalism. The room temperature results are illustrated in Fig. 20. Seki argued that the free and trapping lifetimes... 

Figure 38 The dependence of the hole and electron mobilities on the DMDB to PDA molar ratio in ternary mixtures of DMDB, PDA, and PCZ.

Magin et al. (1995) and Gruenbaum et al. (1996) measured hole and electron mobilities of binary and ternary mixtures containing 4H-l,l-dioxo-4-dicyanomethylidene-2-/ -tolyl-6-phenylthiopyran (PTS), tri-p-tolylamine (TTA), and a polyester (PE). PTS is an acceptor while TTA is a donor. Electron transport in PTS polymers and hole transport in TTA doped polymers have been described previously. For the ternary mixtures, the photocurrent transients were nondispersive over a wide range of fields, temperatures, and concentrations. Values of W were between 0.45 and 0.50 for both electron and hole transients. The presence of the TTA donor did not affect W for electron transients, nor did the presence of the PTS acceptor influence W for hole transients. Figure 40 shows the field dependencies of electron and hole mobilities for a ternary mixture of PTS, TTA, and PE containing 40% PTS and TTA. The temperature was 296 K. The results show that electron and hole mobilities are comparable and show similar field dependencies. The presence of the TTA donor has no significant affect on the electron mobilities, nor does the PTS acceptor have any affect on the hole mobilities. 

Silver-gray cubic crystals, dj 8.16. mp 905°. Most of the crystal is p-type, the n-type material being present in the surface layer. Energy gap 0,27 ev Electron mobility 2240 cm1/volt-sec. Hnle mobility 860 cm1/ volt -sec. Resistivity 0,005 ohm-cm (p-type), 0.00090 ohm-cm (n-type). Not attacked by hydrochloric, hydrofluoric, perchloric and acetic acids or their mixtures not attacked by solns of 30% potassium hydroxide or of alkali metal sulfides. Dil nitric acid turns the surface black, while coned nitric acid produces lighter gray surface and turns the black surface to gray. Hot coned sulfuric acid produces a reddish-violet surface. 

We will first discuss the simple atomic and molecular liquids then results on liquid hydrocarbons will be presented and the section will close with a discussion of the electron mobility in mixtures. 

The studies of electron mobility in liquid mixtures can be classified into two groups. The first group consists of works concerned with the variation of the mobility in binary mixtures over the whole range of concentrations. In the second group of works, the influence of a small concentration of an additional compound is investigated with respect to its influence on the electron transport in a given liquid. 

In the measurement of the electron mobility in liquid mixtures, the following cases have been investigated (1) mixture of a high- and a low-mobility liquid (Bakale et al., 1992 1975b Minday et al., 1972 Sakai et al., 1993a Wada et al., 1977) (2) mixture of two high-mobility liquids (Bakale and Schmidt, 1990 Engels and Van Kimmenade, 1977). 

The electron mobility for case (2) cannot be described by Equation 2. Schiller et al. (1982) applied percolation theory by assuming that the mixture is composed of two microscopic subsystems, each exhibiting the properties of the pure liquid. An equation was derived which describes satisfactorily the concentration dependence of the mobility in this case. 

Figure 10 Electron mobility in mixtures of cyclohexane and Tetramethylsilane at 296 K. (Redrawn from the data of Bakale, G., Lacmann, K., and Schmidt, W.R, Phys, Lett., A168,209,1992.)...

M meth is the electron mobility in pure methane. The data of the methane/ethane mixtures follow Equation 5 up to 0.25 mol fraction of ethane (see Figure 13). 

Bakale, G. and Schmidt, W. E, Mobility of excess electrons in mixtures of neopentane and tetramethylsilane, Chem. Phys. Lett., 175, 319,1990. 

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