The Feasibility of Using Magnetron Sputtered MoO _x as Effective Hole Injection Layer in Organic Light-Emitting Diode

Abstract

Favorite transition metal oxide of MoOx is facilely deposited by using magnetron sputtering process and cast successful application to organic light‐emitting diodes (OLEDs). Magnetron sputtered MoOx is characterized in details with X‐ray diffraction, scanning electron microscopy, atomic force microscopy, X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Magnetron sputtered MoOx shows amorphous structure, superior film morphology, non‐stoichiometry with slight oxygen deficiency and enhanced surface work function, which favorably contributes to hole injection promotion and efficiency improvement. The OLED with magnetron sputtered MoOx as hole injection layer behaves comparable performance to the counterpart with conventional vacuum thermally‐evaporated MoOx. The results demonstrate that magnetron sputtering technique provides an alternative approach for fabricating MoOx interfacial layer in organic electronic devices.

Probing the Crystal and Electronic Structures of Molybdenum Oxide in Redox Process: Implications for Energy Applications

“…The Mo 3d core levels of sample 3 exhibit peaks at 233.2 eV (3d 5/2 ) and 236.3 eV (3d 3/2 ), which are also features of Mo 6+ doublets. All of the major Mo 3d binding energy peaks for samples 2 and 3 are consistent with the previous reports on Mo 6+ in A-MoO 3 , indicating that the oxide layers are amorphous. − In addition, the Mo 3d core levels of sample 4 exhibit peaks at 232.7 eV (3d 5/2 ) and 235.9 eV (3d 3/2 ), agreeing with Mo 6+ of α-MoO 3 . Obviously, the Mo 3d doublets of sample 4 shift to lower binding energies compared to samples 2 and 3, which may be due to the formation of a large amount of α-MoO 3 in sample 4.…”

Metal Oxide Films as Charge Transport Layers for Solution-Processed Polymer Light-Emitting Diodes

“…In the energy levels diagram illustrated in Figure 1d, it is possible to see that a higher work function of MoO x would lead to a lower barrier for charge injection into the PVK. This promotes a better energy level alignment, with bandbending and hole injection capacity, improving charge carrier balance, thus leading to enhanced performance, as has been observed in several reports of OLEDs (smallmolecule based devices) and QLEDs (quantum dotbased devices) assembled with MoO x films deposited by thermal evaporation, 17 sputtering, 38 spin-coating 14,29,39 or blade-coating. 40 It is important to point out that the value displayed for the work function of MoO x in the diagram of Figure 1d was extracted from a few reports on the literature dealing solution-processed MoO x , used as reference.…”