Phosphine-free synthesis of Ag–In–Se alloy nanocrystals with visible emissions

Abstract

As promising heavy metal-free emitting materials, Ag-In-Se nanocrystals (NCs) are conventionally synthesized using organic phosphine agents and exhibit near-infrared emissions. In this work, we demonstrate a rapid phosphine-free approach for synthesizing Ag-In-Se alloy NCs with the emissions tunable to the visible region on the basis of the phosphine-free dissolution of Se powder. At room temperature, Se powder is reduced by dodecanethiol and dissolved in oleylamine to produce a Se precursor. The resultant Se precursor is highly active, which permits rapid synthesis at a relatively low temperature, such as at 90 °C for 150 s. By optimizing the size, structure, and composition, the photoluminescence quantum yield of the as-synthesized Ag-In-Se NCs is enhanced to up to 10%. The growth of the Ag-In-Se NCs involves composition and phase transition, which strongly depend on the reaction temperature. The Ag2Se nuclei form first, and the Ag-In-Se NCs are produced by doping In(3+) into the preformed Ag2Se nuclei. Tetragonal phase Ag-In-Se is obtained below 170 °C, while the orthorhombic phase appears over 190 °C. The potential of Ag-In-Se NCs as red emitting phosphors for lighting-emitting diodes is further demonstrated.

Reaction Tailoring for Synthesis of Phase‐Pure Nanocrystals of AgInSe2, Cu3SbSe3 and CuSbSe2

“…It can also be considered that orthorhombic Ag 2 Se nucleus after insertion of In 3+ ions lead to formation of tetrahedral AISe NCs however, this phase transforms immediately in to orthorhombic at higher reaction temperature (typically above 200 ο C). In recent past, Yao et al have proposed similar reaction pathway as well as phase transformation above190 °C for AISe NCs when synthesized at variable temperature. Similar trend was obtained for samples prepared using oleyl amine instead of oleic acid (Figure (II, a, b, c).…”

“…The peaks obtained at 2θ 33.4, 34.7, 37.0, 40.0, 44.9 ο due to (112), (121), (013), (031) and (032) crystal planes confirming the presence of Ag 2 Se NCs in both of these samples. However, presence of orthorhombic AISe NCs cannot be ruled out since there is an intense peak at 2θ 25.6 ο along with low intensity peaks at 42 ο and 42.8 ο resulted from (202), (040) and (320) crystal planes of an orthorhombic crystal structure . It is thus concluded that the reactions carried out for 3 h and 4 h resulted in formation of Ag 2 Se along with AISe NCs.…”

“…However, phase purity of the sample was established by comparing XRD pattern of AgInSe 2 with the orthorhombic AgInS 2 (JCPDS 00–025‐1328) (Figure S2). The larger atomic radius of Se lead to approximately 2° shift towards smaller angle for AgInSe 2 ,. The comparative 2θ values of AgInSe 2 and AgInS 2 are given in the table S2.…”

Zinc-diffused silver indium selenide quantum dot sensitized solar cells with enhanced photoconversion efficiency

“…This broad emission band (full width at half maxima >100 nm) is an indication of the formation of alloyed QDs. 30 The peak maximum is gradually red shied due to the faster growth of QDs at higher temperatures. The reaction temperature dependent PL spectra of AZ4 and AZ6 QDs (Fig.…”

“…29 The intensity of the lower wavelength band gradually increases with an increase in the reaction temperature which indicates higher incorporation of Zn 2+ and In 3+ into the vacant sites of Ag 2 Se. 14,28,30 At elevated temperatures, these two bands merge into a broad intense emission band. This broad emission band (full width at half maxima >100 nm) is an indication of the formation of alloyed QDs.…”