CuInS₂-Doped ZnS Quantum Dots Obtained via Non-Injection Cation Exchange Show Reduced but Heterogeneous Blinking and Provide Insights into Their Structure–Optical Property Relationships

Abstract

Cadmium-free CuInS2-doped ZnS quantum dots (QDs) are synthesized through a two-step non-injection synthetic method. The resulting QDs are small (∼8 nm or less) and relatively isotropic with photoluminescence quantum yields (PL QY) up to almost 70% and emission peaks in the 560–600 nm window, depending on the amount of the Zn precursor added. The results indicate that small CuInS2 clusters within a zinc blende ZnS lattice are the radiative recombination centers in the nanoparticle. Interestingly, higher ensemble photoluminescence quantum yields (PL QY) result when cation exchange is less extensive (∼80% ZnS composition), while a reduction in blinking is observed when ZnS composition exceeds 99%. A wide heterogeneity in blinking behavior from QD to QD is evident, and a subpopulation statistical analysis shows that the on state dwell times change from multiexponential (or inverse power law) behavior toward monoexponential behavior for particles that spend more of their time in the on state. These results indicate that as the number of CuInS2 emitting centers is reduced, the number of pathways leading to the off state decreases, and a model is proposed to relate this behavior to the QD structure. These results provide a novel route toward CuInS2-doped visible-light-emitting ZnS QDs with high quantum yield and reduced blinking and provide insights into how the composition of the dopant and host matrix affects the radiative recombination mechanisms in single particles.

Unusual Spectral Diffusion of Single CuInS2 Quantum Dots Sheds Light on the Mechanism of Radiative Decay

“…Single-particle spectroscopy has been proven essential to understand various aspects of the photophysics of QDs, as it yields data that are not obscured by ensemble-averaging. − Unfortunately, CIS QDs are notoriously unstable under the harsh excitation conditions used in single-QD experiments. , Consequently, single-particle studies on CIS-based QDs are scarce ,,, and achieve limited data quality compared to studies on other types of QDs. Most strikingly, Whitham et al reported broad single-QD PL line widths (minimum fwhm, 190 meV) from individual core/shell CIS/CdS QDs, whereas Zang et al found narrow PL line widths (minimum fwhm, 60 meV) from individual core/shell CIS/ZnS QDs .…”

Copper sulfide as the cation exchange template for synthesis of bimetallic catalysts for CO2electroreduction

“…The cation exchange method can be further applied to other bimetallic or trimetallic chalcogenides like phase segregated Cu–Au sulfides, 40 Cu–Ni selenides, 56 Cu–Co sulfides nanoboxes, 57 and CuInS 2 -doped ZnS, 58 and could potentially be used for multifunctional photo/electrocatalysis. With modifications of ligands or additives during the cation exchange method, may realize the control of even vs. uneven distribution of two elements with the same overall concentration that can be employed as a great test field for mechanism investigation.…”

Copper Sulfide as the Cation Exchange Template for Synthesis of Bimetallic Catalysts for CO2 Electroreduction

“…The cation exchange method can be further applied to other bimetallic or trimetallic chalcogenides like phase segregated Cu-Au sulfides, 39 Cu-Ni selenides, 53 Cu-Co sulfides nanoboxes, 54 and CuInS 2 -doped ZnS, 55 and could potentially be used for multifunctional photo/electrocatalysis. With modifications of ligands or additives during the cation exchange method, may realize the control of even vs. uneven distribution of two elements with the same overall concentration that can be employed as a great test field for mechanism investigation.…”