Study of the Electronic Structure of the Interfaces Between 2-TNATA and MoO<SUB><I>x</I></SUB>

Abstract

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.

High-performance inverted organic light-emitting diodes with extremely low efficiency roll-off using solution-processed ZnS quantum dots as the electron injection layer

“…One approach is to build an interface dipole moment oriented away from the cathode contact, pulling up the vacuum level of the cathode and lowering the electron injection barrier. 25,26 Wei et al demonstrated the successful application of evaporated ZnS lm as electron injection materials in uorescent and phosphorescent OLEDs to enhance electron injection and mitigate the operation voltage in inverted OLEDs. 27 However, the high-temperature deposited process limited its practical large-scale and low-coat applications.…”