Improved stability and luminescent efficiency of AgInSe₂ nanocrystals by shelling with ZnS

Abstract

In this paper, AgInSe2 (AISe) core and AgInSe2/ZnS (AISe/ZnS) core/shell nanocrystals (NCs) were synthesised by a one-pot method in an organic solvent. Firstly, the synthesis of AIS core NCs with different sizes was performed by hot-injection of Se precursor into the Ag and In complexes at different temperatures from 100 °C to 180 °C for a reaction time of 20 min Then, the ZnS was grown on the surface of AISe NCs at 150 °C for 60 min to produce the AISe/ZnS core/shell structures. The as-synthesised AISe core and AISe/ZnS core/shell NCs were characterised by using x-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and optical spectroscopies (UV–vis absorption and photoluminescence (PL)). After shelling ZnS layer, AISe/ZnS core/shell NCs become more stable (12 months) in ambient air and emit strong luminescence with a high quantum yield (QY) of 40% in the range from 610 nm to 762 nm by varying the reaction temperature of AISe core synthesis from 100 °C to 180 °C. The observed increase of QY and blue-shift in photoluminescence spectra after coating ZnS on surface AISe core NCs are rationalised by the formation of the alloyed structure and passivation of surface states. With their outstanding luminescent properties, AISe core and AISe/ZnS core/shell NCs are very promising in designing emitters for solid-state lighting sources in the greenhouse and in-door farming and bio-related devices.

Multishell Silver Indium Selenide-Based Quantum Dots and Their Poly(methyl methacrylate) Composites for Application in Red-Light-Emitting Diodes

“…The average particle size evidences the growth of the QDs from the original AISe core size of 2.4 ± 0.5–2.8 ± 0.5 nm for the AISe/ZnSe core–shell QDs and 3.4 ± 0.4 nm for the AISe/ZnSe/ZnS core/shell/shell QDs. The small variation in particle size suggests that the process gives to the deposition of a thin layer of ZnSe or ZnS approximately around the monolayer range (∼0.31 nm); similar observations were reported by other authors. , …”

“…The small variation in particle size suggests that the process gives to the deposition of a thin layer of ZnSe or ZnS approximately around the monolayer range (∼0.31 nm); similar observations were reported by other authors. 8,10 XRD and EDS analyses have been used to further clarify the modification of the QDs during the process. The XRD analysis (Figure 3) shows that all the systems present the typical diffraction pattern expected for the AgInSe 2 tetragonal chalcopyrite phase (space group I4̅ 2d), in particular the main diffractions observed in the AISe QD core are centered at 26.2, 43.5, and 51.1°2θ and can be related to the (112), (201, 220), and (312,116) planes, which is in good agreement with the reference pattern for the AgInSe 2 chalcopyrite phase.…”

“…Silver indium selenide is a direct band gap semiconductor with an optical band gap around 1.19 eV observed for the bulk material. − In respect to the more popular sulfide compounds, fewer synthetic approaches are available in the literature for the production of silver indium selenide QDs. This has been mainly related to the different chemical reactivity between the cationic and selenide precursors, which gives poor control over the particle morphology, structure, and chemical compositions, leading to a product characterized by very broad optical features . Some protocols on the aqueous synthesis of silver indium selenides have been recently reported; an example is the coprecipitation reaction of silver nitrate and indium chloride using a freshly prepared sodium selenosulfate (NaSeSO 3 ) solution as a selenium source in the presence of glutathione as a stabilizer .…”

“…For this purpose, ZnSe and ZnS are widely used to produce Core/Shell QDs via epitaxial deposition on a preformed QD. ZnSe and ZnS are of particular interest due to their wide band gap and similar crystallographic structure to the silver indium selenide core, fundamental criteria to confine the photogenerated excitons in the core material while minimizing interface defects. ,, Thick shells have been proven to successfully boost the QDs’ optical properties and stability; however, a large blue shift is typically observed in this condition due to the migration of zinc ions in the core layer producing yellow-green-emitting QDs. ,− For this reason, the preparation of high-quality red-emitting ternary QDs for photonics applications is particularly challenging.…”

“…This has been mainly related to the different chemical reactivity between the cationic and selenide precursors, which gives poor control over the particle morphology, structure, and chemical compositions, leading to a product characterized by very broad optical features. 8 Some protocols on the aqueous synthesis of silver indium selenides have been recently reported; an example is the coprecipitation reaction of silver nitrate and indium chloride using a freshly prepared sodium selenosulfate (NaSeSO 3 ) solution as a selenium source in the presence of glutathione as a stabilizer. 9 Under reflux conditions, sodium selenosulfate decomposes, releasing selenide anions in situ.…”