Chemically Inert Atomic Passivation Shell for Stable Semiconductor Nanocrystals

Abstract

The 2023 Nobel Prize in Chemistry has recognized the important discovery and development of QDs. Colloidal semiconductor nanocrystals (NCs), known as quantum dots (QDs), have attracted increased attention for a wide range of potential applications, such as displays, lighting, photovoltaics, and biological imaging, because of their high quality and size-dependent optical properties. To obtain high-quality semiconductor NCs with reduced surface defects and boosted photoluminescence emission, semiconductor shell-based surface engineering is a commonly used strategy. However, the terminated semiconductor surface is likely not immune to photodegradation or chemical degradation behavior. Insulating matrix encapsulation was demonstrated to be an alternative way to resolve the stability issue, but the bulk and insulating feature of the matrix could restrain the electrical activity and solution processability for device applications of NCs. As a compromise, the chemically inert atomic passivation shell (CIAPS) could be the ideal approach to break the above-mentioned trade-off and promote practical optoelectronic applications. The CIAPS on semiconductor NCs can protect the NCs from the surrounding environment physically and isolate photogenerated excitons from the external photochemical reactions while maintaining access to charge injection or transport for device applications.

In this Account, we summarize our recent progress in the CIAPS strategy on semiconductor NCs. First, we highlight the general consideration of the shell material of CIAPS from the aspects of material stability, the significance of the atomic shell coating, and nondestructive synthesis. Based on these guidelines, chemically stable metal oxide and metallic salt with an atomic thin layer are selected as target CIAPS, and in situ doping (and chemical oxidation) and post-treatment are suitable methodologies. Specifically, we systematically discuss the stabilization effect of the CIAPS strategies on semiconductor NCs, including CdSe, InP, and CsPbX₃. Second, some advanced characterization methods are included in the discussion as well, such as high-resolution aberration-corrected scanning transmission electron microscopy, X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy, chemical etching, and related depth-dependent elemental analysis, facilitating the fundamental understanding of the CIAPS strategy and stabilization mechanism on semiconductor NCs. Third, the CIAPS strategy enables the stabilization of semiconductor NCs on a single-particle level and retains their electrical properties, showing great application potential. Therefore, the important role and potential application of CIAPS are discussed, including electroluminescent LEDs and radiation detection. Finally, the challenges and opportunities are prospected as well to guide the future development of the CIAPS strategy and derived semiconductor NCs. We anticipate this Account could yield more thorough insights for the nanomaterial research community and propel this field further.