Effect of contamination on the electronic structure and hole-injection properties of $MoO3/organic$ semiconductor interfaces

The electronic structure and hole-injection properties of ambient contaminated molybdenum trioxide $(MoO3)$ surfaces are studied by ultraviolet and inverse photoemission spectroscopy, and current-voltage measurements. Contamination reduces the work function (WF), electron affinity (EA) and ionization energy by about 1 eV with respect to the freshly evaporated film, to values of 5.7 eV, 5.5 eV, and 8.6 eV, respectively. However, the WF and EA remain sufficiently large that the hole-injection properties of $MoO3$ are not affected by contamination. The results are of particular importance in view of potential applications of transition metal oxides for low-cost manufacturing of devices in low-vacuum or nonvacuum environment.