Length-dependent inversion of rectification in diblock co-oligomer diodes.

The rectifying direction of diblock co-oligomer molecular diodes is investigated theoretically by analyzing the asymmetric bias effects on the molecular orbitals. The results reveal two competitive mechanisms in determining the rectifying direction, asymmetric energy shift of eigenstates and asymmetric spatial localization of wave functions upon the reversal of bias voltage. It is demonstrated that the dominated mechanism may be converted between the two mechanisms by changing the molecular length, which induces an inversion of the rectification. This work indicates the relative orientation of the two moieties is not sufficient to decide the rectifying direction of co-oligomer diodes. [ABSTRACT FROM AUTHOR]