Aqueous Solution‐Processed Vanadium Oxide for Efficient Hole Injection Interfacial Layer in Organic Light‐Emitting Diode. Issue 11 (17th April 2018) - Zhang, Yan
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 V2 O5 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. Abstract : The ecofriendly process of obtaining aqueous solution‐processed vanadium oxide (VOx ) is explored for hole injection interfacial layers in organic light‐emitting diodes (OLEDs). The device with solution‐processed VOx gives comparable performance to the counterpart with vacuum thermally deposited VOx . Mechanism of VOx promoting hole injection and boosting device performance is clarified in detail.