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Colloidal n-Doped CdSe and CdSe/ZnS Nanoplatelets
Lifeng Wang1,2, Dongmei Xiang1, Kaimin Gao1,2
1State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China.
The Journal of Physical Chemistry Letters
|November 12, 2021
Summary
Chemically doping colloidal semiconductor nanoplatelets (NPLs) with electrons using a photochemical method enables new optical properties. High surface ligand coverage is crucial for stabilizing these n-doped NPLs.
Area of Science:
- Materials Science
- Nanotechnology
- Quantum Optics
Background:
- Colloidal semiconductor nanoplatelets (NPLs) are analogous to quantum wells (QWs).
- Gating and carrier doping are established methods for manipulating QW properties.
- Chemical doping of colloidal NPLs is highly desirable for property control.
Purpose of the Study:
- To achieve n-type doping in colloidal CdSe and CdSe/ZnS NPLs using a photochemical method.
- To investigate the optical properties and stability of doped NPLs.
- To understand the role of surface ligands in the doping process.
Main Methods:
- Photochemical doping of CdSe and CdSe/ZnS NPLs.
- Optical spectroscopy to observe exciton absorption bleaches and intersub-band transitions.
- Analysis of trion binding energies and lifetimes.
Main Results:
- Successfully achieved n-doped CdSe and CdSe/ZnS NPLs via a photochemical route.
- Observed evidence of doped electrons through exciton bleach recovery and near-infrared intersub-band transitions.
- Identified high surface ligand coverage as critical for doping stability.
- Measured large trion binding energies in CdSe NPLs, reduced in CdSe/ZnS NPLs due to dielectric screening.
- Detected a long-lived negative trion (1.5-1.6 ns) in doped NPLs.
Conclusions:
- Photochemical doping offers a chemical route to introduce charge carriers into colloidal NPLs.
- Surface passivation is essential for maintaining doped states in NPLs.
- Dielectric screening in core/shell NPLs significantly affects trion properties.
- Long-lived negative trions exhibit radiative recombination, opening possibilities for optoelectronic applications.
