Midgap state

The single-electron spectrum for the antisoliton solution, A,U)=-Av(x ), is exactly the same as for the soliton, except that now the wave function of the midgap state is given by... 

The 0.5 eV midgap state absorption band is quite prominent but is rather broad. The difference in the midgap energy is 0.7 eV and the absorption peak at 0.5 eV is due to the effect of the electron-electron interaction on the transitions [8], Since the initial state involves two electrons in the midgap level and the final state involves only one, the Coulomb interaction lowers the energy of transition. The 0.5 eV band is quite similar to the midgap absorption in the doped r-PA shown in Fig. 2.2. This demonstrates that this band is associated with the same center in both the photoirradiated and the doped polymers. 

In order to detect the presence of midgap state preferential conduction and, as a consequence, the occurrence of a "0" to V transition, we have investi-... 

In addition, the polarity of the surface modes probably increases at a defect (either charge localisation in the midgap state or oxide bond formation would greatly increase the polarity of the modes (ctp) associated with the surface defect). The increase in polarity naturally leads to a larger modulation of the electron energy within the band and mixing of states for the same rms displacement. 

Midgap state ejfects surface-state trapping... 

The two intragap states y/ x) are the symmetric and antisymmetric superpositions of the midgap states localized near the soliton and the antisoliton ... 

Figure 23 Energy level diagrams for OLED materials. Only the frontier orbitals are considered, (a) Transition from the molecular orbital energies to narrow bands in the solid state to the parallelogram image of the HOMO and LUMO energies are shown, (b) The effect of an applied bias on the energy levels (left). The red arrows illustrate carrier injection via tunneling (tu), thermionic emission (te), or midgap states (mg). The midgap states are shown in blue.

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