Charge carrier mobility factors influencing

Electrochemical reactions are heterogeneous in nature with the reaction kinetics being controlled by the properties of the electrode-electrolyte interface and the concentration of reactant available at this interface. Therefore, the physical, chemical, and electronic properties of the electrode surface are of paramount importance. Several factors will influence the electron-transfer kinetics for a redox system (i) type of electrode material, (ii) surface cleanliness, (iii) surface microstructure, (iv) surface chemistry, and (v) electronic properties (e.g., charge carrier mobility and concentration, which can be potential dependent for some semiconducting electrodes). Of course, if the solid is not a good electrical conductor (low charge carrier mobility and/or carrier concentration), then the current flow will be limited and the material will have drawbacks for electrochemical measurements. With the exception... 

In most cases, point defects constitute the mobile charge carriers of solid and liquid electrolytes. Several factors make the treatment of ionic solids more complicated, however electronic charge carriers frequently contribute to charge transport, nonstoichiometry often influences the defect concentrations, and internal interfaces such as grain boundaries or phase boundaries strongly affect the overall ionic and electronic transport properties. Moreover, each ionic solid represents a separate solvent , whereas liquid electrochemistry predominantly deals with only one solvent, namely water. Because of these intricacies, investigations of transport phenomena in electrolytes are more important in current solid state ionics research than in modern liquid electrochemistry. 

In the designing new molecular architectures, one preliminary objective is finding the relationships among the factors which affect the electronic properties of the final materials. Specifically, the properties one may wish to control in the starting monomer are (i) symmetry, to influence the HOMO bandwidth of the polymer, and hence the mobility of the charge carriers, (ii) 7C-electron conjugation, which should be maintained in the polymer backbone, (iii) oxidation or reduction potential, to favor desired reactions for polymer synthesis, (iv) positional selectivity, to prevent the formation of defects that may interrupt the 7C-conjugation. 

The analytic theory outlined above provides valuable insight into the factors that determine the efficiency of OI.EDs. However, there is no completely analytical solution that includes diffusive transport of carriers, field-dependent mobilities, and specific injection mechanisms. Therefore, numerical simulations have been undertaken in order to provide quantitative solutions to the general case of the bipolar current problem for typical parameters of OLED materials [144—1481. Emphasis was given to the influence of charge injection and transport on OLED performance. 1. Campbell et at. [I47 found that, for Richardson-Dushman thermionic emission from a barrier height lower than 0.4 eV, the contact is able to supply... 

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