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Ultrafast Charge Dynamics in Trap-Free and Surface-Trapping Colloidal Quantum Dots
Charles T Smith1, Marina A Leontiadou1, Robert Page2
1School of Physics and Astronomy and Photon Science Institute University of Manchester Manchester M13 9PL UK.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|December 17, 2016
Summary
Surface traps in colloidal quantum dots significantly impact charge dynamics and recombination. Removing these traps with chloride ions provides new insights into ultrafast charge behavior and data interpretation.
Area of Science:
- Materials Science
- Physical Chemistry
- Nanotechnology
Background:
- Colloidal quantum dots (CQDs) are crucial in optoelectronics.
- Surface traps on CQDs can lead to nonradiative recombination, hindering performance.
- Understanding charge dynamics in CQDs is essential for device optimization.
Purpose of the Study:
- To investigate the effect of surface traps on ultrafast charge dynamics in CdTe CQDs.
- To compare charge dynamics in CQDs before and after surface trap passivation.
- To elucidate the role of surface traps in recombination and exciton behavior.
Main Methods:
- Ultrafast transient absorption spectroscopy (TA) was employed.
- CdTe CQDs were studied before and after treatment with chloride ions.
- Measurements were conducted under static and flowing conditions.
Main Results:
- Surface traps increase electron cooling rates by 70%.
- Traps introduce a subnanosecond recombination pathway for single excitons.
- Surface trapping significantly reduces the peak bleach intensity in TA spectra.
Conclusions:
- Surface traps critically influence ultrafast charge dynamics and recombination pathways in CdTe CQDs.
- Passivation of surface traps with chloride ions alters charge carrier behavior.
- Findings impact the interpretation of TA data, including exciton generation yield estimations.
