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Bandgap Engineering of Indium Phosphide-Based Core/Shell Heterostructures Through Shell Composition and Thickness
Reyhaneh Toufanian1, Andrei Piryatinski2, Andrew H Mahler3
1Division of Materials Science and Engineering, Boston University, Boston, MA, United States.
Frontiers in Chemistry
|December 6, 2018
Summary
Indium phosphide (InP) core/shell nanocrystals offer tunable optical properties for visible to near-infrared emission. Shell composition and thickness precisely control bandgap, photoluminescence, and exciton lifetimes.
Area of Science:
- Materials Science
- Nanotechnology
- Quantum Dot Research
Background:
- Indium phosphide (InP) semiconductor nanocrystals possess a large bandgap and Bohr radius, enabling tunable optical properties.
- Quantum dots (QDs) are crucial for applications requiring precise color tuning, with InP QDs offering advantages over Cadmium Selenide (CdSe).
Purpose of the Study:
- Investigate the impact of core size, shell composition, and thickness on the optical properties of InP/shell quantum dot heterostructures.
- Compare experimental results with effective mass modeling predictions for bandgap energy.
- Demonstrate the tunability of photoluminescence emission across visible and near-infrared (NIR) spectra.
Main Methods:
- Synthesized colloidal InP core nanocrystals with varying diameters (1.5, 2.5, 3.7 nm).
- Fabricated core/shell heterostructures (InP/ZnS, InP/ZnSe, InP/CdS, InP/CdSe) using successive ion layer adsorption and reaction (SILAR) for shell deposition (1-10 iterations).
- Characterized optical properties including bandgap, photoluminescence emission, and exciton radiative lifetime using techniques like transmission electron microscopy (TEM).
Main Results:
- Successfully tuned photoluminescence emission from visible to NIR wavelengths by varying shell composition and thickness.
- Zn-based shells (InP/ZnS, InP/ZnSe) formed type-I heterostructures, with color tuning primarily dependent on core size.
- Cd-based shells (InP/CdS, InP/CdSe) formed type-II heterostructures, emitting in the NIR regardless of core size after multiple shell depositions.
- Observed significant variations (up to 20-fold) in radiative lifetimes at the same particle diameter due to different shell compositions.
- Thicker CdS(e) shells correlated with longer photoluminescence lifetimes, while Zn-based shells showed minimal dependence on shell thickness.
Conclusions:
- InP-based core/shell heterostructures allow precise tailoring of optical properties through controlled variations in core size, shell composition, and shell thickness.
- Type-I (Zn-based shells) and type-II (Cd-based shells) heterostructures exhibit distinct emission behaviors and lifetime dependencies.
- These findings highlight the potential of InP/shell QDs for advanced optoelectronic applications requiring specific spectral emission and lifetime characteristics.
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