Mobility, of charge carriers

The behavior of ionic liquids as electrolytes is strongly influenced by the transport properties of their ionic constituents. These transport properties relate to the rate of ion movement and to the manner in which the ions move (as individual ions, ion-pairs, or ion aggregates). Conductivity, for example, depends on the number and mobility of charge carriers. If an ionic liquid is dominated by highly mobile but neutral ion-pairs it will have a small number of available charge carriers and thus a low conductivity. The two quantities often used to evaluate the transport properties of electrolytes are the ion-diffusion coefficients and the ion-transport numbers. The diffusion coefficient is a measure of the rate of movement of an ion in a solution, and the transport number is a measure of the fraction of charge carried by that ion in the presence of an electric field. 

Another way of obtaining information on the time-averaged mobility of charge carriers on their way across a sample of arbitrary thickness is, to simultaneously measure the current and the stationary charge earners density via transient absorption and to infer the mobility from j-rnpF. Such experiments have been performed on blends of conjugated oligomers derived from /m-siilbene amine and a... 

Microwave Hall experiments have been performed in our laboratory.16 They have shown that the mobility of charge carriers in semiconductors can be measured quite reliably even if the semiconductors are only available in the form of a powder. The measurement technique itself is relatively complicated and involves, for example, rectangular waveguides, which can be rotated against each other on opposite sides of the sample to monitor the phase rotation. In the two-mode resonator, two modes of... 

TABLE 7.1 Electrical Conductivity and Mobility of Charge Carriers in Metals, Band-like Semiconductors, and Hopping Semiconductors... 

Coehoom R (2007) Hopping mobility of charge carriers in disordered organic host-guest systems dependence on the charge-carrier concentration. Phys Rev B 75 155203... 

The electrical conductance of semiconductors is derived from the mobility of charge carriers, holes h+ in the valence band and free electrons e in the... 

The assignment of ti, t2, and t- (see inflection points in Fig. 4.17) to transit times in the top, middle, and bottom layers is supported by the fact that the drift mobility of charge carriers for the three layers were calculated to be similar to the corresponding single layers. The general features of current waveforms described earlier are common to both hole and electron response. 

The dielectric transition is mainly given by the polarization of the space charge and to a lesser extent also by the mobility of charge carriers. 

In any discussion of photoconductivity the importance of the ambient atmosphere and surface must be considered. Not only is the magnitude of the photocurrent dependent on the state of the surface but the provision of guard rings may completely alter the spectral response of the photocurrent. This, it has been suggested, is because the mobility of charge carriers is greater over the surface than through the bulk (35). 

InSb is an important compound semiconductor of the III-V family for optoelectronic purposes. At room temperature the semiconductor has a direct band gap of 0.17 eV and a high mobility of charge carriers. Similar to GaAs, it was reported that InSb can be directly electrodeposited at 45 °C in the Lewis basic chloroin-date ionic liquid InCl3/l-methyl-3-ethylimidazolium chloride, to which SbCU was... 

The network morphology of the phase-separated composite material for enhanced transport and carrier generation. Absorption and mobility of charge carriers has to be maximized within the different components of the bulk heterojunction. 

Enhancement in the performance of OLEDs can be achieved by balanced charge injection and charge transport. The charge transport is related to the drift mobility of charge carriers. Liu et al. [166] reported blue emission from OLED based on mixed host structure. A mixed host structure consists of two different hosts NPB and 9,10-bis(2 -naphthyl)anthracene (BNA) and one dopant 4,4 -bis(2,2-diphenylvinyl)-l,l -biphenyl (ethylhexyloxy)-l,4-phenylene vinylene (DPVBi) material. They reported significant improvement in device lifetime compared to single host OLEDs. The improvement in the lifetime was attributed to the elimination of heterojunction interface and prevention to formation of fluorescence quenchers. Luminance of 80,370 cd/m2 at 10 V and luminous efficiency of 1.8 cd/A were reported. 

Electrical characteristics of organic LEDs are inevitably associated with mobility of charge carriers in materials used for their fabrication. The mobility defined as a carrier drift velocity (v) per unit applied electric field... 

The question arises what is the reason for the high field decrease of (jOg(F). One of them could be a transition from the Langevin to Thomson description of the volume recombination process (see Sec. 1.3). The recombination coefficient y in Eq. (319) cannot be longer expressed by the mobility of charge carriers [see Eq. (4)] and TrecAt follows a field increasing function of the mobility in the numerator of Eq. (319) or/and field-decreasing y. The Thomson-like recombination occurs whenever the capture time (tc) in the ultimate step of the recombination process becomes comparable with the dissociation time (tj) of an initial (Coulombically correlated) charge pair (CP). Such a recombination scheme, depicted in Fig. 172, allows PR to be expressed by Eq. (3). However, to complete this picture, the overall recombination probability should also... 

How both the density and mobility of charge carriers in metals and band semiconductors (i.e. those in which electrons are not localized by disorder or correlation) are influenced by particular features of the electronic structure, namely band dispersion and band Ailing, will now be examined. Taking mobUity first, this book will briefly revisit the topic of band dispersion. Charge carriers in narrow bands have a lower mobility because they... 

THE MOBILITY OF CHARGE CARRIERS IN THE REGION OF SPACE CHARGE... 

The high mobilities of charge carriers found in saturated hydrocarbon liquids suggested that mobile species should also be prevalent in... 

Explain how the conductivity of a material is measured and relate it to the number and mobility of charge carriers (Section 22.5, Problems 21-26). 

From picosecond transient photoconductivity measurements on PPP films,22 we know that mobile charged states decay within 110 ps. In conventional routes to PPPs, defects like branched chains and large torsion angles of neighboring rings are known to occur. These defects act as shallow or deep traps for positive and negative polarons,38,39 which limit the mobility of charge carriers.40 The synthetic route toward the PPP-type ladder-polymers prevents the described defects and leads to a trap concentration of less than 1 trap per 1000 monomer units,28 whereas substi-... 

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