Molecular Additive-Assisted Tellurium Homogenization in ZnSeTe Quantum Dots.

Abstract

The addition of aqueous hydrohalic acids (HX, X = F, Cl, Br) during the synthesis of colloidal quantum dots (QDs) is now widely employed to achieve high-quality QDs. However, this reliance on the use of aqueous solutions is incompatible with oxygen- and water-sensitive precursors such as those used in the synthesis of Te-alloyed ZnSe QDs. Herein, we show this incompatibility, leads to phase segregation into Te-rich and Te-poor regions, causing spectral broadening and luminescence peak shifting under high laser irradiation and applied electrical bias. Here we report a synthetic strategy to produce anhydrous-HF in-situ by using benzenecarbonyl fluoride (BF) as a chemical additive. Through in-situ 19 F nuclear magnetic resonance spectroscopy, we find that BF reacts with surfactants in tandem, ultimately producing intermediary F···H···trioctylamine adducts. These act as a pseudo-HF source that releases anhydrous HF. The controlled release of HF during the nucleation and growth steps homogenizes the Te distribution in the ZnSeTe lattice, leading to spectrally-stable blue-emitting QDs under increasing laser flux from ∼3 μW to ∼12mW and applied bias from 2.6 to 10V. Single-dot photoluminescence (PL) spectroscopy and analyses of the absorption, PL and transient absorption spectra together with density functional theory point to the role of anhydrous HF as a Te homogenizer. This article is protected by copyright. All rights reserved.