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.

Effects of Thermal Lattice Vibration on the Effective Potential of Weak-Coupling Bipolaron in a Quantum Dot

Abstract: Based on the Huybrechts' linear-combination operator, effects of thermal lattice vibration on the effective potential of weak-coupling bipolaron in semiconductor quantum dots are studied by using the LLP variational method and quantum statistical theory. The results show that the absolute value of the induced potential of the bipolaron increases with increasing the electron-phonon coupling strength, but decreases with increasing the temperature and the distance of electrons, respectively; the absolute value of the effective potential increases with increasing the radius of the quantum dot, electron-phonon coupling strength and the distance of electrons, respectively, but decreases with increasing the temperature; the temperature and electron-phonon interaction have the important influence on the formation and state properties of the bipolaron: the bipolarons in the bound state are closer and more stable when the electron-phonon coupling strength is larger or the temperature is lower; the confinement potential and coulomb repulsive potential between electrons are unfavorable to the formation of bipolarons in the bound state.

Bipolarons in Organic Electroluminescence

Abstract: We investigate the bipolaron channel B++ + B−− → BX. The dynamical evolutions and transition probabilities of this bipolaron luminescence channel are studied. It is found that this channel avoids the triplet and is able to enhance the efficiency. We suggest that choosing certain polymers and injection structures, in which B is easily formed, can improve the luminescence efficiency. It is believed that these results will motivate further experimental studies about the function of bipolarons in electroluminescence.

The phase diagram of the 2D Holstein-t-J model near half filling

Abstract: The authors have used an exact diagonalization technique to explore the ground-state phase diagram of the two-dimensional Holstein-t-J model near half filling. The nature of the ground state is analysed, calculating self consistently the local lattice distortions, on-site spin and charge densities, as well as the magnetic structure form factor. They demonstrate that doped holes tend to form hole-polaron or bipolaron states. Compared to that in the uncorrelated model (spinless fermions), the critical electron-phonon coupling strength for the self-trapping transition of the doped charge carriers is considerably reduced by the antiferromagnetic exchange interaction. The relevance to the cuprate superconductors is discussed.

Evolution of the Bipolaronic Structure in Going From One- to Two-Dimensional π Model Systems

Abstract: Long neutral and doubly charged oligodiacetylenes (with a maximum of 30 repeat units) as well as some of their aggregates have been studied in a semiempirical framework. By analyzing the plots of the one-electron ground-state density matrices, we have shown that the 12-units long oligomer is the borderline between two different behaviors of the electronic structure of the isolated charged systems. For oligomers shorter than this limit the bipolaronic structure is the dominant one, while for larger oligomers the polaron-pair structure is preferred. The major conclusion of this work concerns the effects of the interchain interactions in bipolaron systems, which are usually neglected in theoretical works. It is predicted that as a consequence of the latter in the bulk system a bipolaron generated on a single polymer chain will soon split into two polarons on adjacent chains.

Synthesis of polypyrrole having an alkyl side chain

Abstract: Electrochemical polymerisation of 3-octylpyrrole (OCPY) was studied. Its conductivity was 5 S/cm at an optimal current density of 0.5 mA/cm2. Cyclic voltammograms of poly(3-octylpyrrole) (POCPY) films were measured in the presence of various electrolytes and their shapes were virtually independent of the electrolytes used. There was an anodic peak at 0.16 V (versus Ag) and a cathodic peak at 0.12 V. Optical absorption spectra were measured at various levels of doping. The neutral film showed one peak at 3.5 eV, corresponding to the π-π* transition. The oxidised film showed two peaks in the lower energy regions, suggesting it was in the bipolaron state. Scanning electron microscope (SEM) observation revealed a process of unique morphology formation.