MoO3 Films for Efficient Hole-Injection in Organic Electronics

Transition-metal
oxides
(TMO), such as molybdenum tri-oxide (MoO₃), are promising
hole-injection electrode materials for organic electronics because of their
large work function and high conductivity. They are superior to the widely used
organic polymer PEDOT:PSS which causes device degradation. However, deposition
of MoO₃ layers
from high-temperature sources is problematical for flexible organic-based
electronics.

Fig. 1 
AFM image of a film of MoO3 nanoparticles

Kahn et al. have developed a low-temperature method to deposit TMO
films using solution-based processing of nanoparticles of MoO₃ [1]. The nanoparticles, in
suspension in a solvent, are spin-coated onto the target substrate. The
surfactant is then easily removed by a short plasma treatment
(Fig. 1). The current-voltage characteristics of the
deposited MoO₃ layers compare
well with thermally evaporated films, and are
better than PEDOT:PSS (Fig. 2). With the rapid growth
in the commercial applications of nanoparticles, this approach is
promising for large-area manufacturing.

Fig. 2 
How hole-injection from ITO electrodes varies with different
charge-transport layers