Luminescent Quaternary Ag(In_xGa_1–x)S₂/GaS_y Core/Shell Quantum Dots Prepared Using Dithiocarbamate Compounds and Photoluminescence Recovery via Post Treatment

Abstract

Cadmium-free quantum dots (QDs) consisting of silver–indium–gallium–sulfide (AIGS) quaternary semiconductors were successfully synthesized using a metal–dithiocarbamate complex with sufficiently high reactivity to produce metal sulfides. The introduction of a gallium diethyldithiocarbamate precursor decreased the reaction temperature to produce active intermediates, which were subsequently converted into AIGS QDs at 150 °C with silver and indium acetates. Because of the low reaction temperature, AIGS QDs with a tetragonal crystal phase were produced selectively, which favorably generated band-edge emission whose full width at half-maximum is smaller than 40 nm after they were coated with gallium sulfide (GaS y ) shells. The compositional indium/gallium ratio was varied by changing the mixing ratio of the precursors used for the synthesis of the AIGS core, and the band-edge photoluminescence (PL) generated from the AIGS/GaS y core/shell QDs was blue-shifted with an increase in the gallium content in the core. Consequently, a pure green emission centered at 518 nm was obtained with a PL quantum yield as high as 68%.

Surface ligand chemistry on quaternary Ag(InxGa1−x)S2 semiconductor quantum dots for improving photoluminescence properties

“… 22 While uniformly incorporating less-reactive gallium was a substantial challenge, we found that gallium tris( N , N ′-diethyldithiocarbamate) (Ga[DDTC] 3 ) works well owing to its high reactivity in the production of metal sulfides, resulting in the successful synthesis of AIGS QDs at lower temperature; this process involved nearby ions (Ag + and In 3+ ) that were mixed in the reaction solution in the form of acetates. 23 AIGS QDs with different In/Ga ratios were obtained with a well-controlled composition and crystal structure by changing the amount of Ga(DDTC) 3 , which acts as the source of both gallium and sulfur. However, the PL QY of the AIGS QDs decreased significantly upon increasing the amount of Ga(DDTC) 3 , which is due to the electron-accepting nature of the decomposition products of the DDTC ligands that are presumably bound on the surface.…”

Ag2S Nanoparticles Evolved into Luminescent AgInS2@In2S3 Heteronanoparticles through Dual Formation Mechanism

“…[17] Additionally, it was reported that the metal-dithiocarbamate complex had sufficiently high reactivity to produce metal sulfides. [9,[22][23][24][25][26] Based on the above considerations, here, the luminescent AgInS 2 @In 2 S 3 core@shell nanoparticles were fabricated via the reaction of preformed Ag…”

“…[3] Among IB-IIIA-VIA 2 materials, the AgInS 2 nanostructures with direct band gap exhibited strong photoluminescence (PL) in the visible-light wavelength region and had attracted extensive attention in recent research. [5][6][7][8][9] Moreover, it was found that the PL properties of AgInS 2 nanostructures were strongly influenced by the defects, such as the non-irradiative recombination of excited carriers trapped by surface defects (e.g., the dangling bonds on the nanomaterial surface), or the donor-acceptor levels and/or surface traps resulted in the defect emission, [10,11] which was characterized by the large stokes shift and broad emission spectrum. For the application of AgInS 2 nanostructures, how to eliminate defect emission and enhance band edge emission was a very important topic.…”

“…Recently, it had been reported that coating the IIIA-VIA group semiconductor (e.g., InS x or GaS x ) on AgInS 2 core could remove the defect emissions and generate intense narrow band-edge emission of AgInS 2 . [7,9,12,13] Besides, using the organic ligands such as the trioctylphosphine to modify the surface of the AgInS 2 nanoparticles could also improve its band-edge emission, which could be attributed to the irradiative carrier trapping sites passivated by trioctylphosphine bonds. [14] Developing new strategy for synthesizing AgInS 2 nanostructures with the band-edge emission is challenging and significant for their wide application in optoelectronics.The AgInS 2 existed in two crystal forms, including the metastable orthorhombic phase usually formed above 620 °C and the stable tetragonal (chalcopyrite) phase formed below 620 °C, with the bulk bandgaps of 1.98 and 1.87 eV, respectively.…”

“…[14] Developing new strategy for synthesizing AgInS 2 nanostructures with the band-edge emission is challenging and significant for their wide application in optoelectronics.The AgInS 2 existed in two crystal forms, including the metastable orthorhombic phase usually formed above 620 °C and the stable tetragonal (chalcopyrite) phase formed below 620 °C, with the bulk bandgaps of 1.98 and 1.87 eV, respectively. [15] The AgInS 2 could be synthesized using various precursors via many methods, including hot injection and thermo-decomposition using the molecular organic metal precursors, [7,9,16] partial cation exchange using the binary Ag 2 S nanoparticles and molecular In 3+ -precursor, [17] reaction of the Ag 2 S nanoparticles as the source-host with In-S precursor, [18] and partial cation exchange using the binary In 2 S 3 nanocrystals and molecular Ag + -precursor. [19] Actually, in the hot injection A deep understanding of the growth kinetics and mechanism of metal sulfide nanostructure is helpful in preparing nanomaterials with controllable structures.…”