Importance of Surface Functionalization and Purification for Narrow FWHM and Bright Green-Emitting InP Core-Multishell Quantum Dots via a Two-Step Growth Process

Indium phosphide (InP)-based quantum dots (QDs) are widely studied as environmentally friendly light emitters for display applications. However, the synthesis of InP QDs with optical properties that meet high color quality as comparable with cadmium (Cd)- and lead (Pb)-based QDs is challenging. In this article, we present the synthesis of surface-modified bright green luminescence InP core-shell quantum dots (CS-QDs) with the narrowest full width at half-maximum (fwhm) of 33 nm, absolute quantum yield (QY) of 71%, and an absorption spectra valley/depth (V/D) ratio of 0.61 after a size selection purification process. Our approach first emphasizes the heating temperatures for InP growth and second on the importance of surface stabilization of this system. We developed a two-step heating-up process to grow In(Zn)P core and coated inorganic shell with ZnSe/ZnSeS/ZnS composition. In situ surface treatment with zinc chloride (ZnCl2) and 1-octanol was carried out to enhance the PLQY and improve the surface passivation of the CS-QDs. Optical spectroscopy and surface characterization techniques including nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and infrared (IR) spectroscopy were used to analyze the properties of the CS-QDs. We suggest that this work motivates future development and optimization of surface chemistry of InP CS-QDs to enable the full access and realization of their luminescence efficiency in high-color-quality cadmium (Cd)-free displays.

Automated summary

This study presents a method for synthesizing highly efficient InP quantum dots, with a focus on controlling the heating temperature during synthesis and investigating surface stabilization. The surface-modified InP core-shell quantum dots showed narrow full width at half-maximum, high quantum yield, and a high absorption spectra valley/depth ratio after surface treatment and purification.