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