Electron affinity schematic

Schematic energy level diagrams of a metal/polymer/metal structure before and after the layers are in contact are shown in the top two drawings of Figure 11-6. Before contact, the metals and the polymer have relative energies determined by the metal work functions and the electron affinity and ionization potential of the polymer. After contact there is a built-in electric field in the structure due to the different Schottky energy barriers of the asymmetric metal contacts. Capacitance-voltage measurements demonstrate that the metal/polymer/metal structures are fully depleted and therefore the electric field is constant throughout the bulk of the structure [31, 35]. The built-in potential, Vhh i.e. the product of the constant built-in electric field and the layer thickness may be written...

Fig. 15 Simplified schematic representation of the electronic energy levels in a single-layer PLED. CB and VB are the conduction hand and valence hand, respectively, of the semiconducting polymer, which correspond to the ionization potential (IP) and electron affinity (EA) relative to vacuum level (EV). The work functions for anode (and cathode (

Figure 9.5. Schematic of the Sn2 reaction coordinate according to the VBCM model. The energy gaps ER and Ep are identified with sum of the ionization potential and electron affinities of the appropriate species. The avoided crossing occurs at a fraction of ER determined by the reaction enthalpy, AH, and the expected steepnesses of the descending curves. The activation energy for the reaction is E = fER — B, where is the energy of the avoided crossing.

FIGURE 14.4 The general tendency of electron affinity is to be high close to fluorine. However, as this highly schematic representation shows, there is no simple trend. 

Fig. 21. Saturation of residual affinity. Schematic, tangent-circle representations o( electron-domain models of the molecular complexes Me N 1 L> and MesN -111...

Fig. 5. Schematic orbital diagram showing the decrease of the ionization potential and the increase of the electronic affinity upon excitation of a molecule b and a are the highest occupied (bonding) and the lowest unoccupied (antibonding) molecular orbitals in the ground state molecule...

Figure 2.15 Schematic orbital diagram illustrating the relationship between ionization potential (IP) and electron affinity (EA) for the ground and excited states of a molecule and the corresponding ground- and excited-states redox potentials...

FIGURE 1 A schematic of how the UPS spectrum changes for a positive or negative electron affinity [9]. 

Figure 2.3 Schematic representation of CT transitions. EA(A) = electron affinity of species A IP(B) = ionization potential of species B A = stabilization energy of AB. Adapted from ref [19],...

Fig. 2.12. Schematic of a GaAs source of transversely-polarised electrons using photemission from a negative electron affinity GaAs crystal.

FIGURE 5.12. Schematic energy-level diagram for an ITO/PPV/A1 LED, showing the workfunctions, O, of the electrodes and the electron affinity (EA) and ionization potential (IP) of the polymer. The barriers to electron injection (AEe) and hole injection (AEh) are also shown. 

Fig. 19. Schematic representation of the potential energy curves of the ground state of IBr and the lowest states of IBr. This picture is representative for all halogens. Notice however that in the case of a homonuclear halogen only two states remain asymptotically for large R. The very different adiabatic (/tad) and vertical (4,) electron affinities are indicated.

Figure 3.2 shows a schematic energy band diagram of a typical molecular solid. The upper most horizontal line is the vacuum level (Evac)- It is defined as the minimum energy level for an electron to escape from the solid. The energy separation between the HOMO and E ac is the ionization potential (Ip). The separahon between the LUMO and is the electron affinity (3le). 

Fig. 1.4 Schematic Born-Haber cycle for the formation of solid NaCI the energetic data (kJ/mol) are Na sublimation enthalpy AHsubi = 100.5 x CI2 dissociation enthalpy H iss = 121.4 Na ionization energy I = 495.7 Cl electron affinity A = -360.5 experimental reaction enthalpy AHr = -411.1.

Figure 2.67 Energy scheme deduced from the U PS data shown in Figure 2.66. (a) Schematic for conditions (a) and (b) in Figure 2.65, labeled initial and after HCl also shown are cathodic decomposition levels In /ln" and InP/InCl Fovb, conduction and valence band positions after FICl conditioning Xr, electron affinities before and after HCl conditioning AF, energy shift resulting from the treatment, occurring...

Fig. 7.1 Schematic diagram of total electronic energy as a function of fractional occupation number variation, An. Ionization potential (IP) and electron affinity (EA) are defined as E(An = —1) — E(An = 0) and E(An = 0) — E(An = +1), respectively. Based on the Janak theorem, the gradient of the total energy is HOMO energy for An = —0 and LUMO energy for An = +0. The fineariy varied total energies also indicate that the outermost orbital energies are kept constant for the fractional occupation...

FIGURE 10.4 Schematic band diagram of two large bandgap intrinsic semiconductors with different electron affinity before making contact The electron affinities (Ad and Aa are the electron affinity of the donor and the acceptor, respectively) are defined versus the electron energy in vacuum at the same electrical potential. Eqd and Esa is the band gap energy of the electron donor and electron acceptor, respectively. 

In Fig. 5.4a and b the absorption constant and the quantum efficiency, respectively, of a typical CsSb layer are shown as functions of energy. A schematic model for the band structure of the complete photocathode, derived from comparison of absorption data and emission data, is shown in Fig. 5.5 [5.43,57]. The electron affinity is about 0.45 eV and the threshold for efficient photoemission is Th = G+0-45eV,or about 2eV. The band-bending shown is speculative [5.58]. 

In order to facilitate efficient device action, donor and acceptor polymers must possess compatible optical, electronic, and physical properties. Efficient exciton dissociation requires sufficient differences in the electron affinity and ionization potential of the paired polymers. As a rule of thumb, a 0.4 eV difference in the lowest unoccupied molecular orbitals (LUMOs) is typically required to drive dissociation of excitons generated in the donor phase via electron transfer (see Figure 14.2 for a schematic energy level diagram). A similar offset in the highest occupied molecular orbitals (HOMOs) is required to drive dissociation of excitons generated in the acceptor phase via hole transfer. Note that the assignment of donor and... 

Fig. 1.13. A schematic illustration of the spectroscopic techniques and the portion of the band structure that they probe. The techniques illustrated are ionization potential (IP) measmements, electron affinity measurements (Sa), Bremsstrahlrmg isochromat spectroscopy (BIS), Ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), Scanning tunneling spectroscopy (STS)...

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