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.

As F 5 -Doped Polyparaphenylene: Evidence for Polaron and Bipolaron Formation

Abstract: Both elastic and inelastic electron scattering have been used to characterize and investigate the electronic properties of As${\mathrm{F}}_{5}$-doped polyparaphenylene. Evidence is presented for the existence of a polaron state slightly above the top of the valence band at low doping levels. An increase in the doping level first leads to the formation of bipolaron states which broaden and finally form a band in the gap in agreement with recent theoretical predictions.

Polarons in high-temperature superconductors

Abstract: The review deals with the main results of a consistent study of electron-lattice interaction in crystals in the strong-coupling limit. Small polaron and bipolaron formation is shown to provide a number of new physical phenomena both in the normal and superconducting states of the system. Two mechanisms of superconductivity are discussed in detail. The first one arises from the Cooper pairing of small polarons in momentum space (polaron superconductivity). The second one is due to polaron pairing in real space leading to on-site or intersite bipolaron formation with superconductivity analogous to the superfluidity of 4He (bipolaron superconductivity). Highly non-adiabatic motion of (bi)polarons in the narrow band results in fundamental differences of their superconducting state properties with respect to the predictions of the BCS theory and its well known strong-coupling generalization. A number of basic properties of high-temperature metallic oxides being analyzed in terms of (bi)polaron theory of superconductivity is shown to reveal a satisfactory agreement of its findings with the available experimental data.

Ultraviolet photoelectron spectroscopy of poly(pyridine‐2,5‐diyl), poly(2,2′‐bipyridine‐5,5′‐diyl), and their K‐doped states

Abstract: Ultraviolet photoelectron spectra were measured using synchrotron radiation for two kinds of π‐conjugated polymers, poly(pyridine‐2,5‐diyl) (PPy) and poly(2,2′‐bipyridine‐5,5′‐diyl) (PBPy) which exhibit n‐type electrically conducting properties. The two compounds show similar spectra and they were analyzed with MO calculations and the comparison with the data of related molecules. The ionization threshold energies of PPy and PBPy were found to be 6.3 and 6.35 eV, respectively. These values are higher than those of π‐conjugated conducting polymers capable of p doping. Upon potassium doping of PBPy, two new states appeared in the originally empty energy gap and the intensity of the state at 0.65 eV from EF grows as the doping proceeds. This finding and the change of optical absorption spectra upon doping indicate that bipolaron bands are formed in K‐doped PBPy. While K‐doped PPy also shows similar gap states, it requires higher dopant concentration to create bipolaron bands than in the case of K‐doped PBPy....

Effects of temperature and electric field induced phase transitions on the dynamics of polarons and bipolarons

Abstract: The stability of charge carriers in conjugated polymers is investigated in terms of a nonadiabatic evolution method by using an extended version of the Su–Schrieffer–Heeger (SSH) model that includes the effects of an external electric field and temperature. On the basis of this physical picture, different patterns of applied electric field and temperature dependence of polaron and bipolaron kinematics as well as the transitions between different regimes are found. Phase transitions from subsonic to supersonic velocities are also discussed in terms of the system conditions. We were able to describe at which thermal regime each quasi-particle loses its stability and also to determine under which circumstances do the electric field and temperature rise or dampen its motion. The results indicate that thermal effects on polaron and bipolaron stability may provide guidance for improving the charge carrier conduction in organic optoelectronic devices.

Charge storage on a conducting polymer in solution

Abstract: Etude du poly(hexyl-3 thiophene) en solution dans CH 2 Cl 2 ou CHCl 3 et dope par NOPF 6 : difference d'energie faible entre les energies des polarons et des bipolarons, impliquant un controle possible de la repulsion electron-electron en changeant le solvant et/ou la concentration du polymere. Etude du rapport polaron/bipolaron en utilisant differents modeles statistiques. Proposition d'un modele theorique incluant les effets d'ecran ionique sur l'interaction Coulombienne