In order to understand the characteristics of ohmic hole-contacts for the inverted/conventional organic light emitting devices, a hole-only device with all ohmic contacts, which is composed of glass/ITO/MoOx/4,4,4-tris[2-naphthyl-phenyl-amino]triphenylamine (2-TNATA)/MoOx/Al, the elements of the electronic structures of MoOx-on-2-TNATA interface and 2-TNATA-on-MoOx interface were investigated by photoemission spectroscopy, with regards to interface energetics, formative mechanism, and a potential charge carrier injection. The electronic structures revealed that the behavior of the interface between MoOx and 2-TNATA was different whether MoOx was deposited on (2-TNATA) or vice versa. The bottom interfaces of 2-TNATA-on-MoOx in this hole-only devices showed no hole-injecting barrier height (Phi(h)B) when the thickness of 2-TNATA was deposited in the range of 0.1 to 5.0 nm on the 10.0 nm-thick MoOx thin films. This has been explained to be attributed to both metal-induced gap states and a chemical reaction at the interfaces. The top interfaces of MoOx-on-2-TNATA in this hole-only device structure also showed no Phi(h)B when a hole was injected from the MoOx-on-2-TNATA interfaces to cathode. The hole-ohmic property in the top interfaces depends on interface dipole by the formation of charge transfer complexes as well as interdiffusion of MoOx into the 2-TNATA film in these interfaces.

The significant structure theory of liquids' assumes that some molecules possess solidlike, and some gaslike, degrees of freedom and that the relative contributions of each type are given by VS/V and (V-V8)/V, respectively. Here V5 is the molar volume of the solid at the melting point, and V is the molar volume of the liquid. This theory has been successfully applied to a number of liquids2 ranging from liquefied gases, hydrocarbons, molten metals, and fused salts to water and liquid mixtures. Recently, Jhon et al.3 applied the theory with success to simple rocket fuels which have found importance in space programs. In this paper, a further validation of the theory is tested for liquid pentaborane and nitromethane. A partition function is developed and the properties of these compounds are calculated successfully. The Partition Function.-According to the significant liquid structure theory, the partition function of a liquid is written as (Ifsolid fdeg) &NV/V (fgas) N((V-V.)/V) (N(V-V)) ! (1) Here fsolid, fdeg, and fgas are, respectively, the partition functions of the solid, of positional degeneracy, and of the gas; N is Avogadro's number; and the factorial term is due to the indistinguishability of the gaslike molecules. Liquid pentaborane and nitromethane have an abnormally high entropy of fusion (6.48 e.u. for pentaborane4 and 9.48 e.u. for nitromethane5). No solidstate transitions4' 5 have been observed and the increase in volume upon melting is not sufficient to permit the rotation of solidlike molecules in the liquid. Accordingly, the rotational term appears only in the gas partition function, and a six-degree Einstein oscillator term appears in the liquid. The internal rotation of the nitro group in the nitromethane molecule requires discussion. According to Pitzer,6 the potential barrier for rotation of the nitro group is very small (1.1 kcal/mole); consequently, a free rotation of the nitro group is assumed in both the solidlike and gaslike states in the liquid. The earlier models7 of pentaborane were assumed to have a hydrocarbon-like structure of low symmetry. However, several experiments8 with electron diffraction, X-ray diffraction, and Raman spectroscopy revealed an unusual pyramidal structure of C4, symmetry. Considering the above facts, and using standard expressions for f80lid, fgas, and Eyring's expression for fdeg, and applying Stirling's approximation for the factorial term in equation (1), the partition functions for pentaborane and nitromethane take the following forms.