Near-Unity Photoluminescence Quantum Yield of Core-Only InP Quantum Dots via a Simple Postsynthetic InF3 Treatment
Quantum dots (QDs) are luminescent nanomaterials with size-dependent properties, high efficiency, and pure color. These properties make QDs suitable for a wide range of optoelectronic applications, such as displays, solar cells, and bioimaging. InP QDs are considered as the next generation of QDs because they comply with EU safety regulations. Until now, the efficiency of InP QDs without additional capping material has not been high enough to meet application requirements. With our developed treatment using InF3, we reach near unity efficiency for InP QDs. The treatment is applicable to InP from different sizes and made via different synthesis methods making it valuable for all kinds of applications.
Maarten Stam, Guilherme Almeida, Reinout F. Ubbink, Lara M. van der Poll, Yan B. Vogel, Hua Chen, Luca Giordano, Pieter Schiettecatte, Zeger Hens and Arjan J. Houtepen
Abstract
Indium phosphide (InP) quantum dots (QDs) are considered the most promising alternative for Cd and Pb-based QDs for lighting and display applications. However, while core-only QDs of CdSe and CdTe have been prepared with near-unity photoluminescence quantum yield (PLQY), this is not yet achieved for InP QDs. Treatments with HF have been used to boost the PLQY of InP core-only QDs up to 85%. However, HF etches the QDs, causing loss of material and broadening of the optical features. Here, we present a simple postsynthesis HF-free treatment that is based on passivating the surface of the InP QDs with InF3. For optimized conditions, this results in a PLQY as high as 93% and nearly monoexponential photoluminescence decay. Etching of the particle surface is entirely avoided if the treatment is performed under stringent acid-free conditions. We show that this treatment is applicable to InP QDs with various sizes and InP QDs obtained via different synthesis routes. The optical properties of the resulting core-only InP QDs are on par with InP/ZnSe/ZnS core–shell QDs, with significantly higher absorption coefficients in the blue, and with potential for faster charge transport. These are important advantages when considering InP QDs for use in micro-LEDs or photodetectors.
