Charge mobilities

Compounds Method Net charges Mobile bond orders ... 

Insulators lack free charges (mobile electrons or ions). At interfaces with electrolyte solutions, steady-state electrochemical reactions involving charge transfer across the interface cannot occur. It would seem, for this reason, that there is no basis at this interface for the development of interfacial potentials. 

Once the electrons and holes have been injected, they migrate into ETL and HTL to form excited states referred to as polarons by physicists or radical ions by chemists. These polarons or radical ions move, by means of a so-called charge-hopping mechanism, through the electron and hole transport materials (ETMs and HTMs), which typically possess good charge mobility properties, and eventually into the EML. 

Experimentally, the charge mobilities are obtained by time-of-hight-measure-ments or by characterizing held-effect-transistor devices made of the materials. In time-of flight experiments, the mobility p is directly given by... 

Most of the early experimental work [250] has been done on molecular materials imbedded in a polymer matrix at concentrations of 10-80%, so a comparison of the intrinsic properties of the materials is not easy. Another obstacle is the dependence of the charge mobilities on the preparation technology (purity, morphology). However, some data are available for true one-component molecular glasses, a selection of which will be presented in the following sections. 

Charge mobilities determined by the time of flight (TOF) method show that values of 1-10 cm s are not rare for MOMs (Karl et al, 1999). In TOF experiments the transit time r for a sheet of photoinjected carriers to move across a sample of thickness L is monitored. The sheet of carriers is usually generated... 

Bange S, Schubert M, Neher D (2010) Charge mobility determination by current extraction under linear increasing voltages case of nonequilibrium charges and field-dependent mobilities. Phys Rev B 81 035209... 

Warman JM, de Haas MP, Dicker G, Grozema FC, Ptris J, Debije MG (2004) Charge mobilities in organic semiconducting materials determined by pulse-radiolysis time-resolved microwave conductivity 7c-bond-conjugated polymers versus tc—tc-stacked discotics. Chem Mater 16 4600... 

In practice, poor charge mobility, energetic disorder, carrier trapping, and physical aberrations comphcate device characterization. The effects of these nonidealities are often modeled according to an equivalent circuit shown in Fig. 12. Incorporating all specific series resistive elements as R, and all specific parallel resistances as R, one obtains the expression... 

Importantly, both for liquid CgFg and CS2, there is a relatively high yield of ortho-positronium (o-Ps) observed in e irradiation of these fluids [34]. The o-Ps is formed in the e e" recombinations that occur in the end-of-track spurs. The higher the negative charge mobility, the higher the probability that these e e" recombinations occur before the e ... 

The theoretical approaches that have been applied so far to the study of charge mobility in DNA molecules can be divided into two broad classes. 

Electroluminescent polymers, (III) and (IV), both having improved emission and oxidative stability properties were prepared by Son et al. (3) and Park et al. (4), respectively, which offered high charge mobility and blue light emission. 

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