Applications, polymers undoped devices

From Table 2.3, which lists typical // values, it can be seen that the hole mobility in conjugated polymers is lower than that in organic crystals and amorphous silicon, but much larger than that in undoped poly(N-vinyl carbazole). Therefore, conjugated polymers have potential for applications in conducting opto-electronic and photonic devices. In principle, this also applies to liquid-crystal systems that can exhibit enhanced molecular order due to their self-organizing ability, as has been pointed out in a progress report [42]. 

Polymer thin-film field-effect transistors (POLYFETs) have some advantages over the pn- or Schottky-junction devices. In POLYFETs nearly undoped polymers must be used, thus increasing stability and avoiding dopant diffusion. Considering FET applications, the main drawback is the low charge carrier mobility. 

Conductive polymers can be regarded as semiconductors when their conductivity is below 10 S cm h The band gap of undoped ICPs depends not only on the chemical composition but also on the substituents attached to the main chain. Undoped conjugated polymers have found extensive applications for the fabrication of electroluminescent devices. Conductive polymers behave like metallic conductors when they are doped. Both doped and undoped forms of ICPs have an array of potential applications (Table 6.2). 

Although the electrochromism of polymer films contains problems in its relatively slow response and higher electricity consumption due to the redox or doping-undoping reactions in comparison with conventional liquid crystal devices, the rich variations of the coatings, the multi-coloured displays, and the easy construction of large-area devices with polymer films should lead to interesting applications. 

Conjugated polymers, in the undoped state, exhibit the electronic and optical properties of semiconductors in combination with the mechanical properties of general polymers, making them potentially useful for a wide array of applications particularly in organic optoelectronic devices such as polymer LEDs, photodetectors, photovoltaic cells, etc. Development in the performance of such devices has advanced rapidly, and prototype devices now meet realistic specifications for practical applications. In spite of such successful achievements in the scope of device application, however, there is still controversy over the nature of the electronic structure and the appropriate description of the underlying physics of elementary excitations. Since these issues are both scientifically interesting and critically important to the assessment of the future potential of devices based on conjugated polymers, more detailed... 

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