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  • Laser Plasma Process Could Advance Optoelectronic Materials

Photonics.com
Feb 2013
MONTREAL, Feb. 5, 2013 — A novel nanohybrid structure synthesized using a pulsed laser ablation technique could yield a new generation of optoelectronic switches, fast photodetectors and third-generation solar devices.

Research on the photoelectronic properties of semiconductor nanoparticles, such as lead sulfide (PbS), has grown significantly over recent years. Combining PbS with carbon nanotubes for generating photocurrent has proven effective, but the conventional synthesis methods have limitations.

Now scientists at the INRS Énergie Matériaux Télécommunications Research Centre are combining nanoparticles using a relatively simple process that offers considerable latitude for creating other nanohybrids for a variety of applications. The pulsed laser ablation (PLA) technique produces very pure nanostructures with greater control of nanohybrid characteristics.

“When chemically synthesizing nanohybrids, researchers used ligands, which prevented the charge transfer dynamics from nanoparticles to nanotubes,” said professor My Ali El Khakani. Ligands reduce photoresponse efficiency and increase the reaction time — two effects that were not observed in nanohybrids produced using the INRS PLA method, since PbS is in direct atomic contact with the nanotubes’ surface.

“At the beginning, we didn’t know if the nanohybrids would form in such a way as to enable their effective use for photodetection,” said INRS doctoral student Ibrahima Ka. “By optimizing our approach, we developed nanohybrids whose photoactivity can be almost tailored at will.”

Integrating the nanohybrid material into functional photoconductive devices resulted in a stronger photoresponse than was possible with other methods. The INRS researchers achieved photoresponse values as high as 670 percent at 633 nm and 1350 percent at 405 nm; in these conditions, other nanohybrids did not exceed 37 percent.

When illuminated by a laser, the material’s photocurrent response time is 1000 to 100,000 times faster than that of current nanohybrids.

The findings were reported in Advanced Materials (doi: 10.1002/adma.201290298)

For more information, visit: www.inrs.ca


GLOSSARY
photocurrent
The current that flows through a photosensitive device, such as a photodiode, as the result of exposure to radiant power.
quantum dots
Also known as QDs. Nanocrystals of semiconductor materials that fluoresce when excited by external light sources, primarily in narrow visible and near-infrared regions; they are commonly used as alternatives to organic dyes.  
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