Tuning the interfacial stoichiometry of InP core and InP/ZnSe core/shell quantum dots

Abstract

We demonstrate fine-tuning of the atomic composition of InP/ZnSe QDs at the core/shell interface. Specifically, we control the stoichiometry of both anions (P, As, S, and Se) and cations (In, Zn) at the InP/ZnSe core/shell interface and correlate these changes with the resultant steadystate and time-resolved optical properties of the nanocrystals. The use of reactive trimethylsilyl reagents results in surface-limited reactions that shift the nanocrystal stoichiometry to anion-rich and improve epitaxial growth of the shell layer. In general, anion deposition on the InP QD surface results in a redshift in the absorption, quenching of the excitonic photoluminescence, and a relative increase in the intensity of the broad trap-based photoluminescence, consistent with delocalization of the exciton wavefunction and relaxation of exciton confinement. Time-resolved photoluminescence data for the resulting InP/ZnSe QDs show an overall small change in the decay dynamics on the ns timescale, suggesting the relatively low photoluminescence quantum yields may be attributed to the creation of new thermally activated charge trap states and likely a dark population that is inseparable from the emissive QDs. Cluster-model density functional theory calculations show that the presence of core/shell interface anions give rise to electronic defects contributing to the redshift in the absorption. These results highlight a general strategy to

Engineering the Surface Chemistry of Colloidal InP Quantum Dots for Charge Transport

“…Therefore, we include the NOBF 4 treatment following the standard synthesis of tetrahedral InP QDs for the rest of the study. It is also worth noting that the close-to-stoichiometric composition makes these QDs potentially interesting for growing core/shell structures to further enhance PL properties. − …”

Synergistic Effect of Halogen Ions and Shelling Temperature on Anion Exchange Induced Interfacial Restructuring for Highly Efficient Blue Emissive InP/ZnS Quantum Dots

“…[15][16][17][18] To date, considerable research has focused on growth kinetics and synthetic strategies of InP QDs. [19][20][21][22][23][24][25] Apart from the common method where indium acetate and tris(trimethylsilyl)phosphine ((TMS) 3 P) are utilized, indium halide is widely employed in the preparation of InP/ ZnS QDs combining with zinc halide and amino phosphine recently owing to its low cost and safety. As has been reported, halide plays a critical role in its nucleation and surface chemistry.…”

Full-Spectrum InP-Based Quantum Dots with Near-Unity Photoluminescence Quantum Efficiency

“…In the first instance, we used this approach to synthesize InP/ ZnSe QDs emitting at 610 nm after ZnSe shell growth and evaluate the impact of different interfacial treatments in between the InP core formation and the ZnSe shell growth. In view of recent studies reporting a dependence between the InP core composition and the InP/ZnSe band-alignment or emission efficiency, 20,21 and between phosphate (PO 4…”

“…In the first instance, we used this approach to synthesize InP/ZnSe QDs emitting at 610 nm after ZnSe shell growth and evaluate the impact of different interfacial treatments in between the InP core formation and the ZnSe shell growth. In view of recent studies reporting a dependence between the InP core composition and the InP/ZnSe band-alignment or emission efficiency, , and between phosphate (PO 4 3– ) at the core/shell interface and an enhanced PLQY, , we either injected (1) tetrabutylammonium hexafluorophosphate (TBA HFP), (2) water, or (3) a mixture of both in order to achieve better control over the composition of the core/shell interface. As outlined in Supporting Information section S3, these different treatments give rise to a considerable increase of oxidized phosphorus, ranging from 19% to 50 and 75%, as compared to the 6% of oxidized phosphorus found in a reference synthesis without interfacial treatment, while the addition of TBA HFP gives rise to some fluorination of the InP QD surface as well, mostly as partially fluorinated phosphorus.…”