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Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method
Published on: April 18, 2019
Apparent versus true carrier multiplication yields in semiconductor nanocrystals
John A McGuire1, Milan Sykora, Jin Joo
1Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Nano Letters
|May 13, 2010
Summary
Photocharging in semiconductor nanocrystals can inflate carrier multiplication (CM) efficiency measurements. Stirring solutions minimizes this effect, revealing true CM values and resolving discrepancies in solar cell research.
Area of Science:
- Materials Science
- Photovoltaics
- Nanotechnology
Background:
- Carrier multiplication (CM) enhances solar cell performance by generating multiple excitons per photon.
- Semiconductor nanocrystals exhibit CM, typically identified by multiexciton dynamics and Auger recombination.
- Previous studies on CM in nanocrystals have faced discrepancies attributed to experimental conditions.
Purpose of the Study:
- To investigate the impact of uncontrolled photocharging on apparent CM efficiencies in semiconductor nanocrystals.
- To clarify the controversy surrounding CM measurements in nanocrystal systems.
- To establish accurate methodologies for evaluating CM in photovoltaic materials.
Main Methods:
- Comparative measurements of CM efficiencies in static versus stirred nanocrystal solutions.
- Spectroscopic analysis to detect multiexciton dynamics and Auger recombination.
- Quantification of nanocrystal photocharging under varying experimental conditions.
Main Results:
- Apparent CM efficiencies varied by up to 3x between static and stirred solutions due to photocharging.
- Photoinduced charging in static solutions artificially amplified the Auger decay component.
- Accounting for photocharging effects reconciled CM measurements from static and stirred conditions.
Conclusions:
- Uncontrolled photocharging significantly skews CM efficiency measurements in semiconductor nanocrystals.
- Stirring solutions mitigates photocharging, enabling more accurate CM assessment.
- This work provides crucial insights for reliable spectroscopic studies of carrier multiplication in nanomaterials for improved solar energy conversion.
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