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Electronic doping and redox-potential tuning in colloidal semiconductor nanocrystals
Alina M Schimpf1, Kathryn E Knowles1, Gerard M Carroll1
1Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
Accounts of Chemical Research
|June 30, 2015
Summary
Researchers are developing methods to electronically dope semiconductor nanocrystals, making them conductive for advanced electronic devices. This review covers techniques like photodoping and defect doping, crucial for future nanomaterials.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Electronic doping is fundamental to semiconductor technology, enabling conductivity in insulating materials and forming p-n junctions.
- Colloidal semiconductor nanocrystals offer unique properties for new device technologies, driving the need for controlled electronic doping.
- Achieving controlled electronic doping in nanocrystals comparable to bulk materials remains a significant challenge.
Purpose of the Study:
- To review recent advancements in the development and characterization of electronically doped colloidal semiconductor nanocrystals.
- To discuss various successful methods for introducing excess charge carriers into nanocrystals.
- To differentiate between electronic doping and redox-potential shifting and their implications for device performance.
Main Methods:
- Photodoping: Using light to generate charge carriers.
- Outer-sphere electron transfer: Employing external redox agents.
- Defect doping: Introducing specific defects within the nanocrystal structure.
- Electrochemical oxidation or reduction: Applying external electrical potentials.
Main Results:
- Several methods successfully introduce excess band-like charge carriers, including photodoping, outer-sphere electron transfer, defect doping, and electrochemical methods.
- A distinction is made between equilibrium electronic doping and non-equilibrium carrier injection.
- Spectroscopic signatures for excess carriers are reviewed, aiding in distinguishing doping from redox-potential shifting.
- Redox-potential shifting influences charge injection potentials without necessarily creating equilibrium carriers.
Conclusions:
- Electronic doping and redox-potential shifting are valuable for tuning nanocrystal performance in electronic devices.
- Key challenges include sourcing suitable redox-active materials and controlling surface traps, which dictate the Fermi level.
- Controlling nanocrystal surface chemistry is essential for reliable electronic doping strategies.
- Advances in controlling nanocrystal properties promise new electronic nanomaterials for future semiconductor technologies.
