Independent Composition and Size Control for Highly Luminescent Indium-Rich Silver Indium Selenide Nanocrystals

Abstract

Ternary I-III-VI nanocrystals, such as silver indium selenide (AISe), are candidates to replace cadmium- and lead-based chalcogenide nanocrystals as efficient emitters in the visible and near IR, but, due to challenges in controlling the reactivities of the group I and III cations during synthesis, full compositional and size-dependent behavior of I-III-VI nanocrystals is not yet explored. We report an amide-promoted synthesis of AISe nanocrystals that enables independent control over nanocrystal size and composition. By systematically varying reaction time, amide concentration, and Ag- and In-precursor concentrations, we develop a predictive model for the synthesis and show that AISe sizes can be tuned from 2.4 to 6.8 nm across a broad range of indium-rich compositions from AgIn11Se17 to AgInSe2. We perform structural and optical characterization for representative AISe compositions (Ag0.85In1.05Se2, Ag3In5Se9, AgIn3Se5, and AgIn11Se17) and relate the peaks in quantum yield to stoichiometries exhibiting defect ordering in the bulk. We optimize luminescence properties to achieve a record quantum yield of 73%. Finally, time-resolved photoluminescence measurements enable us to better understand the physics of donor-acceptor emission and the role of structure and composition in luminescence.

Heavy Metal Free Nanocrystals with Near Infrared Emission Applying in Luminescent Solar Concentrator

“…The QY was calculated by the formula QY = N emit / N abs as described in the experimental section, where N emit stands for the emitted photons from the NCs and N abs for the absorbed photons by the NCs. The obtained QY value was higher than that of I‐III‐VI NCs in the literature at longer emission wavelength range …”

“…The obtained QY value was higher than that of I-III-VI NCs in the literature at longer emission wavelength range. [2,20,[30][31][32][33][34][35][36][37][38][39][40] The LSCs were fabricated by in situ polymerization of polymethylmethacrylate (PMMA) with a specific amount AIS/ ZnS NCs embedding, and details could be also found in the experimental section. The LSC bulks were illustrated in Figure 5 (a) with the high transparency and standard dimensions of 5 Ã 5 Ã 0.5 cm 3 with a geometric gain ¼ 2.5.…”

Mapping the Atomistic Structure of Graded Core/Shell Colloidal Nanocrystals

“…Analysis of transmission electron microscopy (TEM) images provides independent information on NC size and shape. Here, we first make the approximation that the graded Ag-In-Se/ZnSe core/shell NCs are spherical 16 , and in the section below, show how the results change if the NCs are assumed to be ellipsoidal. From TEM, we define size distribution functions as Gaussians with expectations of 3.9 nm and 4.1 nm and standard deviations of 0.43 nm and 0.49 nm for thin-shell and thick-shell Ag-In-Se/ZnSe NCs, respectively (Fig.…”

“…As a model system, we choose the case of Ag-In-Se/ZnSe core/shell NCs. Upon growth of a ZnSe shell, the luminescence efficiency increases, with current reports of up to 70% quantum yield (QY) for this system 16 . Owing to high miscibility between I-III-VI and II-VI semiconductors and to a large number of cationic defects, which facilitate diffusion 17 , 18 , this system yields graded core/shell structures.…”

Ligand-Mediated Phase Control in Colloidal AgInSe2 Nanocrystals

“…24 Herein, we explore a related ternary chalcogenide, AgInSe2, that is of interest for applications in near-infrared luminescence and as a solar absorber for thin film photovoltaics. [28][29][30][31][32][33] Like CuInSe2, AgInSe2 belongs to the family of I-III-VI2 semiconductors that adopt a thermodynamically preferred chalcopyrite structure in bulk. Possessing an A + B 3+ E 2-2 composition, the diamondoid structure of chalcopyrite can be thought of as a supercell of zinc blende, where the A + and B 3+ cations are ordered in the cation sub-lattice and the Se 2sub-lattice adopts a cubic close packed structure.…”