Highest occupied molecular orbital interface levels

S. Xiao, A. C. Stuart, S. Liu, W. You, Conjugated Polymers Based on Benzo[2,l-b 3,4- b JDithiophene with Low-Lying Highest Occupied Molecular Orbital Energy Levels for Organic Photovoltaics. ACS Appl. Mater. Interfaces 2009, 1,1613-1621. 

S. Xiao, et al. Conjugated polymers based on benzo [2, 1-b 3, 4-b ] dithiophene with low-lying highest occupied molecular orbital energy levels for organic photovoltaics. ACS Applied Materials Interfaces, 2009. 1(7) p. 1613-1621. 

At the donor/acceptor interface (step III in Figure 5), exciton D is quenched via electron transfer to the lowest unoccupied molecular orbital (LUMO) level of the acceptor molecule (A°). On the contrary, exciton A is quenched via hole transfer to the highest occupied molecular orbital (HOMO) level of the donor molecule (D ). Both pathways result in the formation of the same charge separated state D+ A . Positive and negative charges in this ion pair are bond by Coulomb attraction forces and also denoted as geminate polaron pair. This pair can dissociate in the electric field induced by the potential jump at the heterojunction and/or by the difference in the electrode work functions. At the same time, the energy difference... 

Figure 8-1 shows the potential energy barrier for the transfer reaction of redox electrons across the interface of metal electrode. On the side of metal electrode, an allowed electron energy band is occupied by electrons up to the Fermi level and vacant for electrons above the Fermi level. On the side of hydrated redox particles, the reductant particle RED is occupied by electrons in its highest occupied molecular orbital (HOMO) and the oxidant particle OX, is vacant for electrons in its lowest imoccupied molecular orbital (LUMO). As is described in Sec. 2.10, the highest occupied electron level (HOMO) of reductants and the lowest unoccupied electron level (LUMO) of oxidants are formed by the Franck-Condon level sphtting of the same frontier oihital of the redox particles... 

Tables obtained from the Renewable Resource Data Center website at http //rredc.nrel.gov/solar/spectra/ ami.5/. (b) Energy levels and the harvesting of energy from a photon for an acceptor-donor interface within a photoactive layer of a PV cell. The electron affinity and ionization potential are shown as x and IP, respectively. LUMO and HOMO are the lowest unoccupied molecular orbital and highest occupied molecular orbital, respectively. CB and VB represent the conduction and valence bands, respectively. PC and PAn are photocathode and photoanode, respectively. A schematic of the PV cell design for which the above diagram applies is also shown. (Adapted from Saunders, B.R. et al., A[Pg.479]

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