Investigation on carrier injection tailoring and electroluminescence of WSe2 quantum dots in light-emitting diodes

Abstract

WSe2 quantum dots (QDs) with exceptional properties are facilely synthesized with liquid phase exfoliation and hydrothermal reaction, and characterized with scanning electron microscope, atomic force microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The WSe2 QDs show good film morphology and effective carrier injection tailoring. Using 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as emitter, the near ultraviolet organic light-emitting diodes (NUV OLEDs) show maximum radiance of 1.25 mW/cm2 and external quantum efficiency (EQE) of 0.48% in inverted device with WSe2 QDs tailoring electron injection. The corresponding normal UV OLEDs show maximum radiance of 1.82 mW/cm2 and EQE of 1.39% with WSe2 QDs tailoring hole injection. Impedance spectroscopy analysis clarifies carrier injection tunability of WSe2 QDs. LEDs using WSe2 QDs as emitter are pioneeringly fabricated, showing maximum luminance of 426 cd/m2, EQE of 0.39%, luminous efficiency of 0.3 cd/A, power efficiency of 0.13 lm/W, and voltage dependent electroluminescent spectra. Ours results pave an alternative approach for interface modification, developing novel WSe2 QDs emitters, and boosting WSe2 QDs applications.