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Single Trap States in Single CdSe Nanoplatelets
Stijn O M Hinterding1,2, Bastiaan B V Salzmann3, Sander J W Vonk1,2
1Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584CC Utrecht, The Netherlands.
ACS Nano
|March 24, 2021
Summary
Studying trap states in semiconductor nanocrystals reveals that reversible hole trapping causes delayed and near-infrared photoluminescence (PL). This research offers insights into trap state inhomogeneity at the single-particle level.
Area of Science:
- Materials Science
- Quantum Dots
- Nanotechnology
Background:
- Trap states significantly impact semiconductor nanocrystal photoluminescence (PL), causing quenching, delays, and spectral shifts.
- Studying trap states is challenging, especially at the single-trap level, hindering detailed analysis.
- Cadmium Selenide (CdSe) nanoplatelets (NPLs) display notable delayed and near-infrared emission, indicative of trap state activity.
Purpose of the Study:
- To investigate trap states in CdSe NPLs using delayed and trap emission as spectroscopic probes.
- To elucidate the role of reversible hole trapping in influencing photoluminescence properties.
- To characterize trap states at both ensemble and single-particle levels.
Main Methods:
- Utilizing photoluminescence (PL) spectroscopy to analyze delayed emission and near-infrared trap emission from CdSe NPLs.
- Employing single-particle spectroscopy to resolve individual trap state dynamics.
- Correlating delayed PL and trap PL to understand the underlying trapping mechanisms.
Main Results:
- Reversible hole trapping was identified as the source of both delayed and trap PL, originating from the same trap states.
- Single-particle studies revealed exponential decay kinetics for delayed and trap PL, with lifetimes spanning 40–1300 ns.
- Single-trap PL exhibited spectral diffusion and single-photon emission, contrasting with exciton PL.
Conclusions:
- The findings demonstrate that reversible hole trapping is a key mechanism governing delayed and trap emission in CdSe NPLs.
- Single-particle analysis highlights significant inhomogeneity of trap states, even within individual nanocrystals.
- This work provides a deeper understanding of trap state dynamics and their impact on the optical properties of semiconductor nanocrystals.
