Efficient light-emitting diodes from emitters of TaSe2 quantum dots and pure carbon dots and carrier injection tailoring of TaSe2

Abstract

Solution-processed symbiotic TaSe2 quantum dots and carbon dots (TaSe2-QDs/CDs) and pure CDs have been facilely synthesized via liquid-phase ultrasonic exfoliation and hydrothermal reaction. Symbiotic TaSe2-QDs/CDs and CDs show good film morphology and excitation wavelength-dependent photoluminescence. With CDs (TaSe2-QDs/CDs) as emitter, efficient light-emitting diodes (LEDs) are assembled, showing maximum luminance of 217 (640) cd/m2, external quantum efficiency (EQE) of 0.11 % (0.21 %), luminous efficiency of 0.135 (0.262) cd/A, and power efficiency of 0.045 (0.095) lm/W. Resonance energy transfer from CDs to TaSe2-QDs contributes to the enhanced performance in TaSe2-QDs/CDs based LED. With 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as emitters, normal and inverted UV organic LEDs (OLEDs) are realized using TaSe2-QDs/CDs tailoring hole and electron injection, respectively. The normal (inverted) UV OLEDs show maximum radiance of 1.14 (1.3) mW/cm2, EQE of 0.89 % (0.37 %), and electroluminescence peak of 397 (395) nm. Impedance spectroscopy and current versus voltage characteristics are performed to clarify some mechanisms.