Until now, objects on the nanoscale have only been viewable in black and white, but a newly created microscopy tool is now going to change that. With the new tool, it becomes possible to learn much more about the chemistry that occurs on the nanoscale and how different materials interact with light.
The new tool was created by researchers at the Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab). With it, it becomes possible to see the most minute chemical details, many of which have remained undetected until now. The researchers designed the tool specifically to help them learn more about solar-to-electric energy conversion at the nanoscale, but the technology has great promise for use in every area of nanoscience research.
“We’ve found a way to combine the advantages of scan/probe microscopy with the advantages of optical spectroscopy,” says Alex Weber-Bargioni, a scientist at the Molecular Foundry, a DOE nanoscience center at Berkeley Lab. “Now we have a means to actually look at chemical and optical processes on the nanoscale where they are happening.”
The researchers used their new tool to investigate indium-phosphide nanowires. Because they have a nearly ideal band gap of 1.4 electron-volts, these nanowires are ‘perfect’ for converting the Sun’s light to electricity. What the researchers found was something of a surprise. The nanowires have varied optoelectronic properties along their length, not what had been previously thought. This difference could have a substantial effect on how sunlight gets converted to electricity. The researchers also discovered that the relationship between light and electricity, called photoluminescence, “was seven-times stronger in some parts of a nanowire than others. This is the first time anyone has measured these events on such a small scale.”
Weber-Bargioni says: “Details like this about indium-phosphide nanowires are important because if you want to use these suckers for photocatalysis or a photovoltaic material then the length scale at which we’re measuring is where everything happens. This information is really important to understand how, for example, the fabrication and surface treatment of nanowires influences these charge recombination velocities. These determine how efficiently a solar device can convert photons into usable electrons.”
Co-author James Schuck, a nano-optics researcher at the Molecular Foundry, adds: “We realized that this is really the optimal way to do any kind of optical experiment one might want to do at the nano scale. So we use it for imaging and spectroscopy but we anticipate many other uses also.”
The paper, “Mapping local charge recombination heterogeneity by multidimensional nanospectroscopic imaging,” was just published in the journal Science.
Source: DOE/Lawrence Berkeley National Laboratory
Image Credits: DOE/Lawrence Berkeley National Laboratory