Boosting the Photoluminescence Efficiency of InAs Nanocrystals Synthesized with Aminoarsine via a ZnSe Thick‐Shell Overgrowth

Abstract

InAs‐based nanocrystals can enable restriction of hazardous substances (RoHS) compliant optoelectronic devices, but their photoluminescence efficiency needs improvement. We report an optimized synthesis of InAs@ZnSe core@shell nanocrystals allowing to tune the ZnSe shell thickness up to seven mono‐layers (ML) and to boost the emission, reaching a quantum yield of ≈70% at ≈900 nm. It is demonstrated that a high quantum yield can be attained when the shell thickness is at least ≈3ML. Notably, the photoluminescence lifetimeshows only a minor variation as a function of shell thickness, whereas the Auger recombination time (a limiting aspect in technological applications when fast) slows down from 11 to 38 ps when increasing the shell thickness from 1.5 to 7MLs. Chemical and structural analyses evidence that InAs@ZnSe nanocrystals do not exhibit any strain at the core‐shell interface, likely due to the formation of an InZnSe interlayer. This is supported by atomistic modeling, which indicates the interlayer as being composed of In, Zn, Se and cation vacancies, alike to the In2ZnSe4 crystal structure. The simulations reveal an electronic structure consistent with that of type‐I heterostructures, in which localized trap states can be passivated by a thick shell (>3ML) and excitons are confined in the core.

Guilty as Charged: The Role of Undercoordinated Indium in Electron-Charged Indium Phosphide Quantum Dots

“…A true type-I offset is not observed. This can be the result of the small size of the InP core but is likely also the result of electric fields arising at the core–shell interface . Therefore, it is difficult to draw conclusions about the energy offset between the core and the shell.…”

“…This can be the result of the small size of the InP core but is likely also the result of electric fields arising at the core–shell interface. 48 Therefore, it is difficult to draw conclusions about the energy offset between the core and the shell. The coordination number for all In atoms is determined for this model, and it is found that four In atoms are undercoordinated.…”

Synthesis and Single Crystal X-ray Diffraction Structure of an Indium Arsenide Nanocluster

“…The synthesis of highquality InAs QDs has been reported and improved upon for more than 20 years, with much attention paid to the final monodispersity and less to the formation mechanisms. 20,26,41,42,[46][47][48][49][50][51]53 Most reported syntheses use indium carboxylate, a tertiary alkylphosphine, and a reactive silylarsine to nucleate and grow InAs QDs. In studying this precursor system, magic-sized clusters were observed as an intermediate with a characteristic absorption doublet with maxima at 425 and 460 nm.…”

“…One of the QD material systems known to form clusters but lacks structural characterization is InAs. The synthesis of high-quality InAs QDs has been reported and improved upon for more than 20 years, with much attention paid to the final monodispersity and less to the formation mechanisms. ,,,,− , Most reported syntheses use indium carboxylate, a tertiary alkylphosphine, and a reactive silylarsine to nucleate and grow InAs QDs. In studying this precursor system, magic-sized clusters were observed as an intermediate with a characteristic absorption doublet with maxima at 425 and 460 nm. ,,, Even when investigating the usage of germylarsines to improve nanocrystal monodispersity, this characteristic cluster persists .…”

Interface defects repair of core/shell quantum dots through halide ion penetration

“…8–10 These QDs are usually prepared in a core–shell geometry, featuring excellent stability and efficient radiation. 11–15 One critical aspect that significantly affects their optoelectronic properties is the presence of trap states within the band gap, which lead to the localization of charge carriers. 16,17 These trap states are commonly associated with surface and interface defects.…”