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Multiple exciton generation in films of electronically coupled PbSe quantum dots
Joseph M Luther1, Matthew C Beard, Qing Song
1Chemical and Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA. joseph_luther@nrel.gov
Nano Letters
|May 29, 2007
Summary
Multiple exciton generation (MEG) efficiency in lead selenide (PbSe) quantum dot films remains high even with enhanced carrier transport. This finding is crucial for advancing solar cell technologies.
Area of Science:
- Materials Science
- Nanotechnology
- Physical Chemistry
Background:
- Multiple exciton generation (MEG) is a process where one high-energy photon creates more than one electron-hole pair.
- Lead selenide (PbSe) quantum dots (QDs) are promising materials for optoelectronic applications due to their efficient MEG.
- Hydrazine treatment is known to improve carrier transport in PbSe QD films by reducing interdot distances.
Purpose of the Study:
- To investigate the impact of hydrazine treatment on MEG efficiency in electronically coupled PbSe QD films.
- To quantify the MEG quantum yield and absorption cross-section in these films.
- To compare the properties of QDs in films versus isolated QDs in solution.
Main Methods:
- Ultrafast time-resolved transient absorption spectroscopy was employed to study MEG.
- MEG quantum yield was measured and compared to literature values for isolated QDs.
- A modified analysis was used to extract MEG efficiency and absorption cross-section.
Main Results:
- MEG efficiency in PbSe QD films does not decrease after hydrazine treatment, despite enhanced carrier transport.
- The quantum yield was measured to be approximately 4 and 4.5 times the effective band gap.
- Both biexciton lifetime and absorption cross-section were found to increase in films compared to isolated QDs.
Conclusions:
- Enhanced carrier transport via hydrazine treatment does not impede MEG efficiency in PbSe QD films.
- PbSe QD films exhibit favorable properties, including increased absorption cross-section and biexciton lifetime, compared to isolated QDs.
- These findings support the potential of PbSe QD films for efficient photovoltaic applications.
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