(e) Lowest unoccupied molecular orbital
. (f) Highest occupied molecular orbital.
[[lambda].sub.abs,max] [epsilon] [[lambda].sub.em,max] (nm) ([M.sup.-1] (nm) [cm.sup.-1]) 468 30,000 618 [E.sub.ox] (V) (a) [E.sub.LUMO] (versus NHE) [E.sub.0-0] (V) (versus (eV) NHE) 1.28 2.29 -1.01 (a) The LUMO (lowest unoccupied molecular orbital
) level of the dye was calculated using equation [E.sub.ox]-[E.sub.0-0] [47, 48], where [E.sub.0-0] is the zeroth-zeroth transition energy of the dye estimated from the intersection between the absorption and emission spectra of the dye (Figure 2).
For example, Equation 1 for the descendent RLM indicated the negative correlation of the lowest unoccupied molecular orbital
energy ([E.sub.LUMO]) and the sum of negative charges on molecule (TNC), and the positive correlation of the energy Gap ([E.sub.gap]) and the activation energy (Ea).
A low density of defect states within the highest occupied molecular orbital to lowest unoccupied molecular orbital
(HOMO-LUMO) gap of poly(3-hexylthiophene) (P3HT) has been observed [2, 3].
The electronic properties such as highest occupied molecular orbital ([E.sub.HOMO]) energy, lowest unoccupied molecular orbital
([E.sub.LUMO]) energy, and the energy gap ([E.sub.g] = [E.sub.LUMO] - [E.sub.HOMO]), the dipole moment ([mu]) were calculated.
In this context, many groups [1-4] studied their photoluminescence (PL), but the PL was usually very weak because the HOMO-LUMO (highest occupied molecular orbital to lowest unoccupied molecular orbital
) optical transition is dipole forbidden owing to the high molecular symmetry.