中国科技论文在线-凯发网

in this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model hamiltonian. we calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. we analyze the physical process of the injected electron in this multilayer system. it is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields.

by using extended ssh hamiltonian plus long-range electron correlation hamiltonian model, we calculated charge injection and spin polarization in a ferromagnetic metal/polymer/ferromagnetic metal structure. we adjust relative chemical potential between the ferromagnetic materials and the polymer to control charge transfer. it is found that when spin orientations of two ferromagnetic materials are parallel to each other, spin-polarized single polaron can be formed in the polymer, but when the spin orientations of two ferromagnetic materials are antiparallel to each other, bipolaron is formed and that spin polarization is found to be zero inside the polymer. the influence of the long-range electronic correlation on these polarons in the polymer is discussed

a general formula of the long-range correlation energy ec for the π electron systems is given, which includes diagonal interactions and off-diagonal interactions and we put forward to a correlation hamiltonian at the first time. it is found that the effects of the off-diagonal interactions w and x on the correlation energies are opposite. the effect of w is to increase the correlation energies, but the effect of x is being counteracted by the integral term j due to |x|～|j |. the long-range correlation energies decrease with increasing the screening effect. at normal screening, the influence of w on the correlation energies can be neglected.

a general formula of long-range electron correlation energy in excited states ofπelectron systems is presented for the first time. effect of excited states upon the long-range electron correlations, which are related to problems of exciton and polaron, is discussed. it is found that because charge density distributions are different for removal (addition) of an electron from (into) π electron system, the correlation energies of electron-type polaron and hole-type polaron are not the same even when the system tends to infinity.

the present study calculates correlation energies of the different length poly(pphenylenevinylene) (ppv) units using the formula recently developed for π conjugated polymers, and analyzes the correlation energies from the phenylene unit and the vinylene unit in single and three ppv unit cells as well as the effect of the correlation energies on the band energy gap of the ppv. the present method avoids the complicated numerical computations about the correlation effects for the π electronic conjugated molecule systems with large unit cells.