Electronic structure of conjugated polymers

Both theoretical and experimental evidence suggest that the precise nature of the charge carriers in conjugated polymer systems varies from material to material, and it is still a subject of debate in many cases. A discussion of the various theoretical models for the electronic structure of conjugated polymers is given below, using polyacetylene and poly(paraphenylene) as examples. More detailed information on these materials and the applicability of these theoretical models is given in subsequent sections. 

Dobrosavljevic V, Stratt R (1987) Role of conformational disorder in the electronic-structure of conjugated polymers substituted polydiacetylenes. Phys Rev B 35 2781-2794... 

RECURRENT VARIATIONAL APPROACH APPLIED TO THE ELECTRONIC STRUCTURE OF CONJUGATED POLYMERS... 

To conclude, we have presented in this note the Recurrent Variational Approach and, more specifically, its first application to the electronic structure of conjugated polymers. The ansatz built here (26), shows some nice similarities with the trial state (3) made for the two-leg ladder. 

Recurrent variational approach applied to the electronic structure of conjugated polymers 169... 

In this section the electronic structure of conjugated polymers is discussed. They form a special class of materials with particular types of excitations (such as the solitons) and properties, introduced briefly in Chapter 11. These problems are discussed here essentially in relation to the spectroscopic properties. The related but distinct subject of electrical conductivity is treated in Section IV. To set the scene, we first present some typical results visible absorption and emission spectra and resonance Raman spectra. We consider the theoretical issues in Section III.B, then return to the meaning of the experimental results in Section III.C. The interesting nonlinear optical properties of CPs will be considered in Section III.D. These sections are concerned with electronic states within the gap or near the band edges the structure (i.e., the dispersion relations) of valence and conduction bands is also of theoretical interest and is considered in Section III.E. 

The electronic structure of conjugated polymer semiconductors reflects the complex interplay between intrinsic rr-electron delocalization along the polymer backbone and strong electron-phonon coupling, and the existence of energetic and positional disorder in solution-processed thin films. In a hypothetical, infinitely straight polymer chain, the highest occupied molecular orbital (HOMO) and lowest unoccupied... 

Li, L. Collard, D.M. Tuning the electronic structure of conjugated polymers with fluoroalkyl substitution alternating alkyl/perfluoroalkyl-substituted polythiophene. Macromolecules 2005, 38, 372-378. 

W. R. Salaneck, R. H. Friend, J. L. Br das, Electronic Structure of Conjugated Polymers Consequences of Electron-Lattice Coupling. Phys. Rep. 1999,319, 231-251. 

FIGURE 1.6 Schematic representation of the electronic structure of conjugated polymers according to (a) hand theory and (b) a molecular picture. 

High absorption cross section for photon harvesting. Ideally, the electronic structure of conjugated polymers is that of a one-dimensional semiconductor in which the absorption coefficient increases steeply above the band gap absorption. The absorption coefficient of the frequently used poly(p-phenylene vinylene) polymer MDMO-PPV (Figure 10.2.) reaches 10 cm just... 

The dimerized chain is the simplest model of semiconducting polymers, and is applied in particular to trans-polyacetylene. The noninteracting electronic structure of conjugated polymers with more complex unit cells, such as poly(para-phenylene), will be discussed in their relevant chapters. We emphasize that the noninteracting model is a simple model. It is not a realistic description of the electronic states of conjugated polymers, as it neglects two key physical phenomena electron-phonon coupling and electron-electron interactions. Despite these deficiencies it does provide a useful framework for the more complex descriptions to be described in later chapters. 

Strong intersite coupiing leads to the formation of uncorrelated electron-hole pairs, in which the optical transition is described appropriately using a band description [103]. The electronic structure of conjugated polymers was described by Su et al. [2,3] (SSH model) in terms of a quasi-one-dimensional tight-binding model in which the tt electrons are coupled to distortions in the polymer backbone by the electron-phonon interaction. Photon absorption makes an electron jump from the HOMO to the LUMO band (n—tt transition). This transition creates free carriers, which subsequently self-localize, thereby forming nonlinear excitations of... 

In this paper, I will review recent work on certain aspects of the electronic structure of conjugated polymers, and try to make contact with the work on the electronic structure of short oligomers. It is impossible to cover this vast subject except by ignoring a great deal. I therefore do not pretend to be exhaustive instead I will cover a few topics of current concern and hope that these overlap sufficiently with the interests of people studying the properties of polydiacetylenes. 

Non-Linear Excitations and the Electronic Structure of Conjugated Polymers... 

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