Electronic semiconductor polymer

Polymers play important roles in water photolysis. For multi-electron processes, polymer supported metal colloids or colloidal polynuclear metal complexes are very useful as catalysts. Unstable semiconductors with a small bandgap which photolyse... 

In contrast to metals and semiconductors, the valence electrons in polymers are localized in covalent bonds.The small current that flows through polymers upon the application of an electric field arises mainly from structural defects and impurities. Additives, such as fillers, antioxidants, plasticizers, and processing aids of flame retardants, cause an increase of charge carriers, which results in a decrease of their volume resistivity. In radiation cross-linking electrons may produce radiation defects in the material the higher the absorbed dose, the greater the number of defects. As a result, the resistivity of a radiation cross-linked polymer may decrease. Volume resistivities and dielectric constants of some polymers used as insulations are in Table 8.3. It can be seen that the values of dielectric constants of cross-linked polymers are slightly lower than those of polymers not cross-linked. 

The properties are very sensitive to composition and the charge carriers are apparently positive. Other studies have shown poly(acenaph-thalene) to be only slightly photo-conductive while the nitrated polymer exhibits a photocurrent dependent upon the degree of nitration (100). Since the number of mobile n electrons is the same as in poly (vinyl naphthalene), the authors conclude that some form of stereoregularity is required for enhanced conductivity. Complexes of poly(vinyl anthracene) with halogen molecules show enhanced conductivity and reduced activation energy which is thought to be typical of an electronic semiconductor (101). 

J. L. Bredas, W. R. Salaneck and G. Wegner (Eds), Organic Materials for Electronics Conjugated Polymer Interfaces with Metals and Semiconductors (North Holland, Amsterdam, 1994). 

P. Dannetun, M. Fahlman, C. Fauquet, K. Kaerijama, Y. Sonoda, R. Lazzaroni, J. L. Bredas and W. R. Salaneck, in Organic Materials for Electronics Conjugated Polymer Interfaces with Metals and Semiconductors, J. L. Br6das, W. R. Salaneck and G. Wegner (Eds) (North Holland, Amsterdam, 1994), p. 113. 

Fig. 10.2. One-dimensional semiconductor model of interacting 2/>z-electrons in polymer chain from C-C- bonds of alternating length (it-electron system of polyacetylene) [9] (a)-the configurations of chain with repeat union 2a (b)-energy band scheme for 2/>z-electrons G the gap between valent and conduction bands.

When an electron is added (by doping with donors or by photoexcitation) to the NDGS semiconductor polymer, it does not go into the conduction band as is the case in a conventional semiconductor. It deforms the polymer chain as shown in Fig. 2.4. The actual... 

Not all these cited studies have focused on photodriven HER and OER applications for the coated semi-conductor/electrolyte interfaces. Ae.c.p.= electronically-conducting polymer, sc = semiconductor... 

Just as polymers may be used to form printable semiconductors, so they may be used to form dielectrics as well. Indeed, polymer dielectrics are in widespread use in conventional microelectronics as well. For printed electronics applications, polymer dielectrics are therefore a natural choice for use in printed transistors. Several families of polymer dielectrics have been studied and used in printed transistors. These include various polyimides and other polymer dielectrics such as pol)rvinylphenol (PVP). In general, these dielectrics are characterized by the following properties ... 

The silicon surface can be stabilized using surface modification techniques which are divided into three categories (1) attachment of redox mediator which consumes the holes on the surface (2) attachment of electronically conducting polymer and (3) coating with thin metal or semiconducting films to create a buried semiconductor interface. Combinations of these approaches can also be used to stabilize the sihcon surface. ... 

The materials sciences continue to bring forth new electronically conducting solids (2-4). Virtually all of these have possible applications in electrochemical systems. Among the more interesting candidates in recent times have been semiconductors, electronically conducting polymers, intercalation materials, new forms of carbon, and oxide and sulfide compounds, especially the perovskites. A wide variety of applications could arise from these materials, including new or... 

The photophysics of jt-conjugated polymers are reviewed in detail in other chapters of this book. (See, for example, Chapter 3.) Here, we focus on the electronic and photophysical phenomena that occur at the heterojunction between two different semiconductor polymers. The heteroj unctions are formed by combining four different polyfluorene copolymers in blend or bilayer thin films and are investigated using time-resolved and steady-state, temperature- and elec-tric-field-dependent photoluminescence measurements as well as electroluminescence and time-resolved spectroscopy. We review a body of work carried out in our laboratories over the last few years, and published in numerous journal articles (see refs. [13-17]). 

The aim of this chapter is to elucidate the various electronic and optical processes that occur at heterojunctions between two semiconductor polymers. Most of the results presented are related to the presence of localized electronic states at heterojunctions between different polyfluorenes. These have an analog in solution systems of small molecules where they are called exciplex states. Here, we give an overview of the theories that have been developed for small-molecule solution systems (for more details see also [24] and [25]). In Section 2.1.3, we then discuss if and how these are applicable to solid-state films of blended conjugated polymers. 

Electronic Processes at Semiconductor Polymer Heterojunctions 2.1.4.2 The PFB F8BT Exciplex... 

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