Zinc Oxo Clusters Improve the Optoelectronic Properties on Indium Phosphide Quantum Dots

This study explored the effect of zinc precursors on the optical properties of InP quantum dots (QDs) by controlling the reactivity of zinc carboxylates via a simple thermal treatment. The formation of zinc oxo clusters, Zn4O(oleate)6 and Zn7O2(oleate)10, during the thermal decomposition of zinc oleate was confirmed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry. Using zinc oxo clusters as reaction precursors, high-quality InP QDs with a high photoluminescence quantum yield (PLQY) and a narrow full width at half-maximum (FWHM) were synthesized (green QDs: PLQY = 95%, FWHM = 37 nm; red QDs: PLQY = 84%, FWHM = 40 nm). The analysis results showed that improved optoelectronic properties were achieved by two important functions of the zinc oxo clusters: (1) suppressing the rapid depletion of the highly reactive phosphorus source and inducing size uniformity of the In(Zn)P core, and (2) facilitating the formation of an oxidized buffer layer, which effectively controls defects. Likewise, the use of reactivity-controlled species is an effective strategy for the synthesis of well-designed QDs.