  An electrode contact-related mechanism for the operational instability of
organic electronic devices is proposed and confirmed via observation of a
water-induced change in charge-injection barrier eights at the
electrode/organic-semiconductor interfaces. Water molecules in air penetrate
into the organic crystal via diffusion, and an external electric field orients
the electric dipole of the water molecules at the electrode surfaces, leading
to dipolar switching of the charge-injection barrier height. As a result of the
switching, current-voltage curves of two-terminal Au-rubrene-Au devices change
from symmetric to asymmetric, showing diode-like rectification and reversible
switching of the diode polarity. The device shows the highest current switching
ratio of 267 for the switching voltage of 3 V, corresponding to an electrode
work function change of >144 meV. The mechanism proposed herein will be
important especially for short-channel organic devices, which are indispensable
for applications such as organic integrated circuits.
