Abstract
Highly luminescent silver indium sulfide (AgInS2) nanoparticles were synthesized by dropwise injection of a sulfur precursor solution into a cationic metal precursor solution. The two-step reaction including the formation of silver sulfide (Ag2S) nanoparticles as an intermediate and their conversion to AgInS2 nanoparticles, occurred during the dropwise injection. The crystal structure of the AgInS2 nanoparticles differed according to the temperature of the metal precursor solution. Specifically, the tetragonal crystal phase was obtained at 140 °C, and the orthorhombic crystal phase was obtained at 180 °C. Furthermore, when the AgInS2 nanoparticles were coated with a gallium sulfide (GaSx) shell, the nanoparticles with both crystal phases emitted a spectrally narrow luminescence, which originated from the band-edge transition of AgInS2. Tetragonal AgInS2 exhibited narrower band-edge emission (full width at half maximum, FWHM = 32.2 nm) and higher photoluminescence (PL) quantum yield (QY) (49.2%) than those of the orthorhombic AgInS2 nanoparticles (FWHM = 37.8 nm, QY = 33.3%). Additional surface passivation by alkylphosphine resulted in higher PL QY (72.3%) with a narrow spectral shape.
Highlights
Luminescent semiconductor nanoparticles, or quantum dots (QDs), have attracted attention over the past two decades due to their unique optical and electronic properties owing to the quantum size effect [1,2]
The AgInS2 core QDs were synthesized by introducing the oleylamine solution of DMTU into preheated metal precursor solutions
As a result of the studies on reaction mechanism, we have demonstrated that the AgInS2 NPs were produced through the Ag2S intermediate NPs, and the morphology of the AgInS2 NPs strongly depended on the generation speed of the Ag2S NPs and their conversion to AgInS2
Summary
Luminescent semiconductor nanoparticles, or quantum dots (QDs), have attracted attention over the past two decades due to their unique optical and electronic properties owing to the quantum size effect [1,2]. These cadmium-free QDs possess band gap energies in the visible region as well as large optical absorption coefficients, which are characteristic for direct semiconductors [9,10,11,12,13] Among these QDs, silver indium sulfide (AgInS2) nanoparticles (NPs) with a band gap energy of 1.87 eV have attracted increasing attention [14,15]. The thermal decomposition of a single molecular precursor was used to avoid the reactivity problem, which resulted in a high (~50%) PL QY for AgInS2-ZnS NPs [17,18,19] The limitations of this method are the necessity of designing a molecular precursor for each composition and the difficulty of controlling the particle size and shape due to the complexity of the decomposition process [20]. The control over particle size and composition was achieved, none of these attempts generated a narrow band-edge emission corresponding to common II–VI semiconductor QDs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
