External electric field and UV-ozone treated Ti₃C₂T _x -MXene nanosheets and their hole injection tailoring in UV organic light-emitting diodes

Solution-processed 2D nanosheets of Ti3C2T (x) -MXene have been facilely synthesized with ultrasonic-assisted liquid phase exfoliation. X-ray diffraction, scanning electron microscope, transmission electron microscope, atomic force microscopy and x-ray photoelectron spectroscopy measurements confirm that the Ti3C2T (x) -MXene nanosheets have been successfully synthesized, showing good film morphology and exceptional electronic properties. The comprehensive properties of Ti3C2T (x) -MXene nanosheets are systematically optimized by combination with appropriate sizes of Ti3C2T (x) -MXene nanosheets, external electric field and ultraviolet (UV)-ozone treatment. With Ti3C2T (x) -MXene nanosheets as hole injection layer and PBD as emissive molecule, UV organic light-emitting diodes (OLEDs) have been configurated and shown superior performance with maximum radiance of 1.47 mW cm(-2), maximum external quantum efficiency of 1.084% and electroluminescent peak around 400 nm. The effects of external electric field and UV-ozone treatment on hole injection ability of Ti3C2T (x) -MXene nanosheets are investigated in details and further analyzed with impedance spectroscopy. Our experiments pave an alternative approach for advancing Ti3C2T (x) -MXene nanosheets and UV OLEDs.