Enhanced Photoluminescence Quantum Yield of Colloidal MoS₂ Quantum Dots by Optimization of Oleic Acid and Oleylamine for Light-Emitting Diode Applications

Abstract

In this study, we investigate the impact of oleic acid and oleylamine on the photoluminescence quantum yield (PLQY) and size distribution of MoS 2 quantum dots (QDs) synthesized by using the colloidal heating method. The optical characteristics of MoS 2 QDs are found to be dependent on OAc/OAm (mL/mL) concentrations, which are (0 mL/0 mL), (0 mL/3 mL), (3 mL/0 mL), (3 mL/3 mL), (3 mL/6 mL), and (6 mL/3 mL). The optimal amount of OAc is obtained to be 3 mL with a high PLQY and narrow size distribution of QDs with an average diameter of ≈3 nm. A maximum PLQY of 12.32% is measured for (3 mL/0 mL) QDs with blue emission showing PL maxima at ≈440 nm, while for (3 mL/3 mL) and (3 mL/6 mL), the measured PLQY values are 9.12 and 7.00%, respectively. For the remaining OAc/ OAm combinations, the measured PLQY value is ≈3% with wide-size distributions. Morphological analysis using a transmission electron microscope reveals the spherical QD formation for all the different OAc/OAm combinations. FTIR results show the presence of C−H, C�O, C�C, and C−N, confirming OAc and OAm coverage on the MoS 2 QD surface. We report the highest achieved PLQY of 12.32% for colloidally synthesized blue-emitting MoS 2 QDs. With high PLQY, these QDs can find applications in light-emitting diode fabrication, sensing, and bioimaging.