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Bipolaron

About: Bipolaron is a research topic. Over the lifetime, 1335 publications have been published within this topic receiving 29154 citations. The topic is also known as: bipolarons.


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Journal ArticleDOI
TL;DR: In this paper, a simple Raman spectra treatment is used to obtain a quantitative characterization of polyaniline films, and the potentiality of the Raman Spectroscopy (RS) is pointed out.

148 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared two different models that treat weakly interacting organic/metal (and organic/organic) interfaces: the induced density of interfacial states model and the so-called integer charge transfer model.
Abstract: The fundamentals of the energy level alignment at anode and cathode electrodes in organic electronics are described. We focus on two different models that treat weakly interacting organic/metal (and organic/organic) interfaces: the induced density of interfacial states model and the so-called integer charge transfer model. The two models are compared and evaluated, mainly using photoelectron spectroscopy data of the energy level alignment of conjugated polymers and molecules at various organic/metal and organic/organic interfaces. We show that two different alignment regimes are generally observed: (i) vacuum level alignment, which corresponds to the lack of vacuum level offsets (Schottky-Mott limit) and hence the lack of charge transfer across the interface, and (ii) Fermi level pinning where the resulting work function of an organic/metal and organic/organic bilayer is independent of the substrate work function and an interface dipole is formed due to charge transfer across the interface. We argue that the experimental results are best described by the integer charge transfer model which predicts the vacuum level alignment when the substrate work function is above the positive charge transfer level and below the negative charge transfer level of the conjugated material. The model further predicts Fermi level pinning to the positive (negative) charge transfer level when the substrate work function is below (above) the positive (negative) charge transfer level. The nature of the integer charge transfer levels depend on the materials system: for conjugated large molecules and polymers, the integer charge transfer states are polarons or bipolarons; for small molecules' highest occupied and lowest unoccupied molecular orbitals and for crystalline systems, the relevant levels are the valence and conduction band edges. Finally, limits and further improvements to the integer charge transfer model are discussed as well as the impact on device design.

140 citations

Journal ArticleDOI
TL;DR: In this paper, self-consistent field calculations are carried out on various polyenes with emphasis on defect configurations designed to simulate soliton and polaron excitations in polyacetylene.
Abstract: Semiempirical self-consistent-field calculations are carried out on various polyenes with emphasis on defect configurations designed to simulate soliton and polaron excitations in polyacetylene. For defect-free polyenes, the calculated bond-length alternation ($\ensuremath{\Delta}r=0.106$ \AA{}) is in close agreement with generally accepted values for polyacetylene. Solitons and polarons are simulated on polyene radicals, ions, and radical ions by the introduction of appropriate symmetries and by charging; these are viewed as neutral (radical) and charged (cation and anion) defects in the polyene structure. The equilibrium geometries and charge distributions of varying-length polyenes and defect-containing polyenes are calculated. The extent of disruption of the bond-length alternation pattern of the carbon backbone is predicted to be about half as large as previously thought for neutral defects (solitons) and even smaller for anionic defects. Positively charged solitons are of larger extent. These results are consistent with known conductivity---doping-level relationships. A spatially damped charge-density wave is associated with the charged solitons and a spin-density wave with the neutrals; in both cases the wave extends farther than the lattice kink itself. Polarons and bipolarons, studied as soliton-antisoliton pairs (radical cations and radical anions) on the same model molecule, are also found to exhibit charge-density-wave solutions. The bipolaron is shown to be unstable to the formation of a like-charge soliton-antisoliton pair. Strong interchain coupling is expected as a result of the large dipole moments associated with the unique form of the lattice polarization due to the damped charge-density wave in charged solitons and polarons.

138 citations

Journal ArticleDOI
TL;DR: It is found that bipolaron formation typically requires strong impurity interactions beyond the validity of more commonly used weak-coupling approaches that lead to local Yukawa-type interactions.
Abstract: Mobile impurities in a Bose-Einstein condensate form quasiparticles called polarons. Here, we show that two such polarons can bind to form a bound bipolaron state. Its emergence is caused by an induced nonlocal interaction mediated by density oscillations in the condensate, and we derive using field theory an effective Schr\"odinger equation describing this for an arbitrarily strong impurity-boson interaction. We furthermore compare with quantum Monte Carlo simulations finding remarkable agreement, which underlines the predictive power of the developed theory. It is found that bipolaron formation typically requires strong impurity interactions beyond the validity of more commonly used weak-coupling approaches that lead to local Yukawa-type interactions. We predict that the bipolarons are observable in present experiments, and we describe a procedure to probe their properties.

134 citations

Journal ArticleDOI
TL;DR: In this paper, a quantitative study of polaron and bipolaron formation in polypyrrole upon electrochemical doping is presented, where the steady-state spin concentration has been measured as a function of the electrical potential in an in situ ESR-electrochemical experiment and the charge injection has been determined by coulometry and by optics.

134 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202229
202127
202023
201920
201833