Photophysics of Conjugated Polymers

Photophysics of Conjugated Polymers
Author: Tieneke E. Dykstra
Publisher:
Total Pages: 326
Release: 2008
Genre:
ISBN: 9780494578650

Download Photophysics of Conjugated Polymers Book in PDF, Epub and Kindle

Poly (para-phenylenevinylene) (PPV), and its derivatives such as poly [2-methoxy, 5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] (MEH-PPV), are typical conjugated polymers. In order to implement conjugated polymers into processable electronics technologies, we must first understand their complex photophysical properties as their efficiencies depend on the balance between exciton recombination and charge carrier formation. The inherent complexities of these materials arise from entanglement of the pi-electron system with disorder and nuclear motions of the polymer backbone. This disorder breaks the polymer chain into conformational subunits which can couple, giving rise to a set of delocalized states formed by Coulombic interactions between proximate subunits. Characteristics of PPVs include high quantum yields, non-mirror image absorption and fluorescence line shapes, and large apparent Stokes' shifts. These properties are discussed in the context of the relationships between polymer conformation, electronic structure, coupling, disorder and polymer photophysics.These important influences are often manifest in the dynamics of what happens after photoexcitation. In this work, we present 3-pulse photon echo peak shift (3PEPS) studies of conjugated polymers in both solution and film. To elucidate timescales characteristic of relaxation processes, we have simulated the 3PEPS data simultaneously with absorption and fluorescence, observing a rapid localization of the exciton in the initial ∼ 20 fs. Additional contributions to the decay of the peakshift are discussed. We also present transient anisotropy data for PPV polymers and oligomers which is compared to dynamics simulation for isolated chains of PPVs. This work demonstrates the influence of microscopic structure on ultrafast dynamics. We show that relaxation between exciton states can lead to rapid depolarization of the anisotropy, even though the spatial extent of exciton migration may be small. Generally, the connection between conformation and electronic structure is a theme throughout this thesis.

Optical and Electronic Properties of Fullerenes and Fullerene-Based Materials

Optical and Electronic Properties of Fullerenes and Fullerene-Based Materials
Author: Joseph Shinar
Publisher: CRC Press
Total Pages: 400
Release: 1999-11-24
Genre: Science
ISBN: 9780824782573

Download Optical and Electronic Properties of Fullerenes and Fullerene-Based Materials Book in PDF, Epub and Kindle

This text covers a host of fullerene applications, including nanotubes, compounds of fullerenes with other elements and structures and polymerized fullerenes. It discusses properties of photoexcited states of fullerenes, neutral and charged states, nonlinear optical response (NLO) and electron-electron interactions.

Enhanced Photophysics of Conjugated Polymers

Enhanced Photophysics of Conjugated Polymers
Author:
Publisher:
Total Pages:
Release: 2003
Genre:
ISBN:

Download Enhanced Photophysics of Conjugated Polymers Book in PDF, Epub and Kindle

The addition of oppositely charged surfactant to fluorescent ionic conjugated polymer forms a polymer-surfactant complex that exhibits at least one improved photophysical property. The conjugated polymer is a fluorescent ionic polymer that typically has at least one ionic side chain or moiety that interacts with the specific surfactant selected. The photophysical property improvements may include increased fluorescence quantum efficiency, wavelength-independent emission and absorption spectra, and more stable fluorescence decay kinetics. The complexation typically occurs in a solution of a polar solvent in which the polymer and surfactant are soluble, but it may also occur in a mixture of solvents. The solution is commonly prepared with a surfactant molecule:monomer repeat unit of polymer ratio ranging from about 1:100 to about 1:1. A polymer-surfactant complex precipitate is formed as the ratio approaches 1:1. This precipitate is recoverable and usable in many forms.