Increase solar efficiency with nano matchsticks
(Nanowerk News) Researchers in Australia have demonstrated a highly efficient mechanism for extracting energy from metal nanocrystals, with potential benefits in photovoltaics, photocatalysis and optoelectronics.
Based at RMIT University and CISRO, a team led by Exciton Science created nanometer-sized ‘matchsticks’ – tiny structures made of gold nanorods and a cadmium selenide tip.
The metal tip of the matchstick structure operates like an antenna to catch light, and its interaction with the tip results in the accumulation of an electric charge.
By creating an optimal structure, the researchers demonstrated the potential to achieve charge extraction efficiencies of up to 45%.
This study is an indication of the promise this approach holds for important energy harvesting and industrial applications, including solar-powered hydrogen production.
The results have been published in a journal ACS nano (“Optimal Geometry for Extraction of Plasmonic Heat Carriers in Metal-Semiconductor Nanocrystals”).
Led by PhD candidate Lesly Melendez and Associate Professor Daniel Gomez from RMIT, the work focuses on the extraction of charges via plasmons, a term for the collective oscillations of electrons in metals.
When a photon of light with a certain energy level is absorbed by a material, it drives the movement of electrons from the metal to the semiconductor, which is called ‘hot electron transfer’.
However, efficiently collecting charge from plasmons (and understanding their behavior) is difficult, because plasmons ‘relax’ and release their energy very quickly.
The team used a research technique called single particle electron energy loss spectroscopy (EELS) to better understand the relationship between the structure and function of metal-semiconductor systems.
EELS is a high-resolution electron microscopy-based technique useful for studying nanocrystals as it provides a direct correlation between function and detailed information about particle size, geometry and composition.
Several previous studies have demonstrated the potential of EELS to evaluate electron and energy transfers between metal nanoparticles and semiconductor materials.
By applying it to the structure of the gold nanorods, the researchers were able to discover some of the highest levels of plasmonic heat carrier generation reported to date.
EELS allowed them to identify which parameters control charge separation efficiency, including the quality of the interface between the gold and cadmium selenide and the size of the metal ingot.
The findings should support the best future design approaches for these structures, which can feature state-of-the-art synthesis mechanisms that can create efficient nanostructures at large scales.