Aqueous Solution‐Processed Vanadium Oxide for Efficient Hole Injection Interfacial Layer in Organic Light‐Emitting Diode

Abstract

Solution‐processing techniques have effectively promoted low‐cost and large‐scale manufacturing of organic light‐emitting diodes (OLEDs). An ecofriendly process is demonstrated here to obtain aqueous solution‐processed vanadium oxide (s‐VOx) for effective hole injection interfacial layer (HIL) by using commercial V2O5 powders. Atomic force microscopy and X‐ray photoelectron spectroscopy measurements show that s‐VOx exhibits superior film morphology and non‐stoichiometry with slight oxygen deficiency which account for exceptional electronic properties in tailoring hole injection. With tris(8‐hydroxy‐quinolinato)aluminum as emitter, s‐VOx‐based OLED gives a maximum luminous efficiency of 6.4 cd A−1 and power efficiency of 4.1 lm W−1, which are comparable to those (6.1 cd A−1 and 3.6 lm W−1) of vacuum thermally deposited VOx‐based counterpart. The current versus voltage characteristics and impedance spectroscopy of hole‐only devices elucidate that s‐VOx possesses robust hole injection capacity and thereby promotes the OLED performance. Our results pave an alternative approach for broadening VOx application with solution process and accelerating OLED development.

Room-Temperature Photodeposited Amorphous VOx Hole-Transport Layers for Organic Devices

“…Solution-processed VO x HILs in OLEDs have also been reported to be advantageous. − In addition to OPV devices, OLED devices made with VO x as the HIL were fabricated and contrasted with devices made with PEDOT:PSS, using an architecture of ITO/HTL/super yellow /PFN/Ag; these were fabricated in a manner similar to OPV devices. Estimated layer thicknesses are PEDOT:PSS: 30 nm, VO x : 5 nm, super yellow: 80 nm, PFN: 10 nm, and Ag: 100 nm.…”

Highly Efficient All-Solution-Processed Quantum Dot Light-Emitting Diodes Using MoOx Nanoparticle Hole Injection Layer

“…In addition, due to the nature of organic materials, the PEDOT:PSS has a lower thermal stability than inorganic materials. Transition metal oxides such as molybdenum oxide (MoO 3 ) [ 26 , 27 , 28 ], nickel oxide (NiO) [ 29 , 30 , 31 ], tungsten oxide (WO 3 ) [ 32 , 33 , 34 ], and vanadium oxide (V 2 O 5 ) [ 35 , 36 , 37 ] have successfully been employed in QLEDs as promising alternatives to replace the organic PEDOT:PSS HIL due to their compatibility with a high work function, good stability, and good carrier mobility. Consequently, transition metal oxides have applications in various devices, including photovoltaics, batteries, and light-emitting diodes.…”