Polymer semiconductors

Colvin, V. Schlamp, M. and Alivisatos, A. P. (1994). Light-emitting diodes made from cadmium selenide nanocrystals and a semiconductor polymer. Nature, 370,354-357. 

Third, metallocene units, such as ferrocene or ruthenocene, have been linked to phosphazene cyclic trimers or tetramers and these were polymerized and substituted to give polymers of the type mentioned previously (41). Polyphosphazenes with ferrocenyl groups can be doped with iodine to form weak semiconductors. Polymer chains that bear both ruthenocenyl and ferrocenyl side groups are prospective electrode mediator systems. 

Polymers consisting of but not limited to poly thiophene, polypyrrole and poly aniline have been extensively used to make polymer nanofibers. In general, any metal that can be electroplated has most likely appeared in a nanowire. Semiconductors, polymers, and insulators have also been used in the design of nanowires.Furthermore, different metals can be plated in succession to give striped nanowires. 

Composition Containing Thiazole Rings, Organic Semiconductor Polymer... 

Identical methods for investigation of photoconductivity can be used for inorganic and organic semiconductors. Polymer semiconductors as a rule have very high resistance. For such materials the main information about the photoconductive mechanisms and properties may be obtained by two methods electrophotographic (or discharge method) and time of flight (or transit method). Both methods are successfully applied for materials with low mobilities, less than lO-4m2 V-1 s-1, which are the usual values for polymer semiconductors. 

Under constant experimental conditions, the number of Raman scattered photons is proportional to analyte concentration. Quantitative methods can be developed with simple peak height measurements.5 Just as with IR calibrations, multiple components in complex mixtures can be quantified if a distinct wavelength for each component can be identified. When isolated bands are not readily apparent, advanced multivariate statistical tools (chemometrics) like partial least squares (PLS) can help. These work by identifying all of the wavelengths correlated to, or systematically changing with, the levels of a component. Raman spectra can also be correlated to other properties, such as stress in semiconductors, polymer crystallinity, and particle size because these parameters are reflected in the local molecular environment. 

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... 

I. PHOTOEXCITATION PHOTO-INDUCED ABSORPTION, PHOTO-INDUCED BLEACHING AND PHOTOCONDUCTIVITY Photo-excitation studies of conjugated semiconductor polymers were stimulated by the calculations of Su and Schrieffer (IJ. which demonstrated that in trans-fCH) an e-h pair should evolve into a pair... 

In summary, semiconductor polymers such as polyacetylene and polythiophene have experimentally demonstrated nonlinear optical processes (photo-induced absorption, photo-induced bleaching and photo-luminescence) with characteristic time scales in the picosecond range or faster. These phenomena are intrinsic and originate from the instability of these conjugated polymers toward structural distortion. 

In the next sections we discuss some selected examples of the use of ATR spectroscopy to study semiconductors, polymers, and corrosion processes. 

Quantum dots dispersed in organic semiconductor polymer matrices... 

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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