The optical excitation of the molecule is associated with the electron jump from the HOMO to the LUMO, so that each frontier MO becomes occupied by a single electron. As a result, even at an unbiased regime of electron transmission, owing to the molecule-electrode couplings (the respective electron hopping matrix elements are βλ, r k , (r = 1, 2, λ = L, H, cf. Eq. (4) ), the molecular charge can vary due to electron exception at the HOMO or electron release from the LUMO.
The depicted kinetic processes are valid in the framework of HOMO-LUMO model for the molecular device.
Transmission gaps in the 1M2 device.
The transient sequential and the direct components of the photocurrent (solid and dashed curves, respectively) (a), and the temporary behavior of the molecular populations (b). The insert in panel (a) shows the time evolution during the fast phase.
The transient sequential (a) and direct (b) components of the photocurrent and the temporary behavior of the molecular populations (c). The inserts in panels (a) and (b) demonstrate the time evolution during the fast phase. The parameters are the same as in Fig. 4 except J HL (cf. Table I ). A strong decrease of the steady state photocurrent is observed in comparison with those from Fig. 4 .
The transient sequential and direct components of the photocurrent (panel (a) and the insert in the panel, respectively) and the temporary behavior of the molecular populations (b). The parameters are the same as in Fig. 5 except and (see Table I ). A strong increase of the maximal value of the sequential current component and a noticeable decrease of the steady state photocurrent are observed in comparison with those from Fig. 5 .
A decrease of the steady state photocurrent with the rise of energy splitting E S − E T = J HL between the excited singlet and triplet molecular states. At the chosen transmission gap ΔE −S = −0.2 eV, the change of transmission regime occurs in the region around J HL = 0.2 eV (shaded).
Set of parameters used in the computations (for explanation see text).
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