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Broadband and picosecond intraband absorption in lead-based colloidal quantum dots
Bram De Geyter1, Arjan J Houtepen, Sergio Carrillo
1Photonics Research Group, INTEC Department, Ghent University-IMEC, Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium.
ACS Nano
|June 13, 2012
Summary
Lead chalcogenide nanocrystals exhibit significant photoinduced absorption below the band gap. This broadband infrared response is crucial for developing ultra-high-speed all-optical signal processing technologies.
Area of Science:
- Materials Science
- Nanotechnology
- Optoelectronics
Background:
- Lead chalcogenide nanocrystals are promising materials for optoelectronic applications.
- Understanding their photoinduced optical properties is essential for device optimization.
Purpose of the Study:
- To investigate the photoinduced absorption (PA) in lead chalcogenide nanocrystals.
- To elucidate the origin of the PA signal and its relevance for optical applications.
Main Methods:
- Femtosecond transient absorption spectroscopy was employed to study the dynamics of photogenerated carriers.
- Tight-binding calculations were used to confirm experimental observations.
Main Results:
- Lead chalcogenide nanocrystals show broad photoinduced absorption just below the band gap.
- The PA signal decay correlates with band gap recovery, indicating involvement of photogenerated carriers.
- Intraband absorption was identified as the mechanism responsible for the PA signal.
Conclusions:
- The observed intraband absorption in lead chalcogenide nanocrystals provides a broadband response in the near- to mid-infrared range.
- This property is highly relevant for ultra-high-speed all-optical signal processing.
- Performance was benchmarked against bulk silicon and silicon nanocrystals.
