Topic
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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TL;DR: The lowest-energy state of C 60 is discovered to be a ringbipolaron exciton which is qualitatively consistent with the self-trapped polaron exciton observed in the luminescence experiment of neutral C 60.
Abstract: Neutral fullerene C 60 is studied by the electron-lattice-coupling tight-binding model. When one or two electrons are excited from the highest occupied molecular orbital to the lowest unoccupied molecular orbital of a C 60 molecule, the lattice relaxes and the lowest-energy state of C 60 is discovered to be a ringbipolaron exciton which is qualitatively consistent with the self-trapped polaron exciton observed in the luminescence experiment of neutral C 60 . The symmetry of optical excitation C 60 is reduced from I h to Dsa and it is proposed that four NMR lines would be observed in this material
16 citations
TL;DR: In this paper, the ratio of the surrounding mediums' static to high-frequency dielectric constants is especially large, e0/e∞ > 2, and a planar large bipolaron in p-doped La2CuO4 is defined.
Abstract: Planar-large-bipolarons can form if the ratio of the surrounding mediums’ static to high-frequency dielectric constants is especially large, e0/e∞ >> 2. A large-bipolaron in p-doped La2CuO4 is mode...
16 citations
TL;DR: In this paper, electron spin resonance measurements on a disordered conducting polymer were performed from 4 K up to 400 K for the first time in order to investigate the nature of the so-called "Pauli-like" regime.
Abstract: Electron spin resonance measurements on a disordered conducting polymer were performed from 4 K up to 400 K for the first time in order to investigate the nature of the so-called "Pauli-like" regime. The usual departure of the susceptibility from a Curie law, a shift in the g-factor value and a transition from a line broadening regime to a line narrowing one were observed for T > 200 K. We argue that all of these high-temperature ESR properties are due to thermal excitation of bipolarons from the singlet to the triplet state. The appearance of Pauli paramagnetism is ruled out for this system. A detailed discussion of the susceptibility, spin relaxation and g-factor is given.
16 citations
TL;DR: It is shown that large bipolaron densities can exist near electrode interfaces and that they are linked to the phenomenon of unipolar organic magnetoresistance, which indicates that bipolarons are generally expected to be significant near contacts in the Fermi level pinning regime and thus may be more prevalent in organic electronic devices than previously thought.
Abstract: Bipolaron states, in which two electrons or two holes occupy a single molecule or conjugated polymer segment, are typically considered to be negligible in organic semiconductor devices due to Coulomb repulsion between the two charges. Here we use charge modulation spectroscopy to reveal a bipolaron sheet density >1010 cm−2 at the interface between an indium tin oxide anode and the common small molecule organic semiconductor N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine. We find that the magnetocurrent response of hole-only devices correlates closely with changes in the bipolaron concentration, supporting the bipolaron model of unipolar organic magnetoresistance and suggesting that it may be more of an interface than a bulk phenomenon. These results are understood on the basis of a quantitative interface energy level alignment model, which indicates that bipolarons are generally expected to be significant near contacts in the Fermi level pinning regime and thus may be more prevalent in organic electronic devices than previously thought. Bipolarons - two electrons or holes localized on the same molecule - are generally considered negligible in organic electronic devices. Dhanker et al. show that large bipolaron densities can exist near electrode interfaces and that they are linked to the phenomenon of unipolar organic magnetoresistance.
16 citations
TL;DR: In this article, the stability of a bipolaron as a function of the strength of the Coulomb interaction in conjugated polymers was studied, and it was shown that impurities and image forces tend to stabilize the bipolaron.
16 citations