Diffusion doping process

The doping process (here of the p-type) takes place with formation of the charged polycation accompanied by diffusion of the electrolyte counterion X ... 

As repeatedly stressed, the doping processes imply the diffusion of electrolyte counterions to compensate for the electric charge assumed by the polymeric chain and thus polymers are expected to experience changes of mass upon doping. Consequently, by monitoring these changes it is possible to control the nature and the extent of the doping processes. 

Since the kinetics of the doping processes is expected to depend upon the nature of the counterion, particularly its size (which may influence the mobility throughout the polymer host), it is possible to control the diffusion kinetics by selecting the nature of the supporting electrolyte employed in the electrodeposition process. 

The wafers are processed into solar cells, the majority of which have a diode structure, as sketched in Figure 11.4, characterized by a thin, diffused, doped emitter, screen-printed front and back contacts and a front-surface antireflective coating. Prior to the effective cell manufacturing step, a chemical treatment of the silicon wafers removes... 

As intensive studies on the ECPs have been carried out for almost 30 years, a vast knowledge of the methods of preparation and the physico-chemical properties of these materials has accumulated [5-17]. The electrochemistry ofthe ECPs has been systematically and repeatedly reviewed, covering many different and important topics such as electrosynthesis, the elucidation of mechanisms and kinetics of the doping processes in ECPs, the establishment and utilization of structure-property relationships, as well as a great variety of their applications as novel electrochemical systems, and so forth [18-23]. In this chapter, a classification is proposed for electroactive polymers and ion-insertion inorganic hosts, emphasizing the unique feature of ECPs as mixed electronic-ionic conductors. The analysis of thermodynamic and kinetic properties of ECP electrodes presented here is based on a combined consideration of the potential-dependent differential capacitance of the electrode, chemical diffusion coefficients, and the partial conductivities of related electronic and ionic charge carriers. 

A general view ofthe mechanisms and kinetics of the doping processes (using EIS), and a quantitative evaluation of the chemical diffusion coefficients of electronic and ionic charge carriers with the use of small-amplitude techniques (often called potentiostatic and galvanostatic intermittent titration techniques PITT and GITT, respectively [29]). 

Modified by the addition, as applicable, of impurity diffusion (doping), ion implantation, epitaxy, etc. The active surface is processed into arrays of discrete devices or integrated circuits by metallization, passivation, or other means metallization of its back side (bottom surface) is optional. 

These sets of data of the diffusion coefficients are different by several orders of magnitude and cannot be understood easily within the frame of our knowledge about the PAn redox chemistry. Nonetheless, it is clear that anion exchanges are involved during doping and de-doping processes of the PAn film. More studies need to be carried out to fully understand the phenomena. 

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