According to the British Science News website, high-energy "hot" electrons are expected to help solar panels collect light energy more efficiently. But scientists have been unable to measure the energy of those electrons, which limits their use. Researchers at Purdue University and the University of Michigan have invented a method to analyze these energies.
Vladimir Sharayev, a distinguished professor at the School of Electronics and Computer Engineering at Purdue University, said: "There are many theoretical models of thermal electrons, but there has never been a direct experiment or measurement about what they look like." Responsible for the Purdue University team in collaborative research.
In a paper published in the US weekly "Science" published on June 4, the researchers demonstrated a method that uses scanning tunneling microscope combined with laser and other optical components to reveal the thermal electron energy distribution.
Hasha Reddy, PhD student and principal author of the paper at the School of Electronics and Computer Engineering at Purdue University, said: "Measuring energy distribution means quantifying the number of electrons under a certain energy.
The way to generate hot electrons is usually to illuminate the nano-structured gold or silver metal with a specific frequency to stimulate the so-called "surface plasma". It is believed that these plasmas will eventually lose some of their energy to the electrons, making them hot.
The temperature of hot electrons can be as high as about 1100 degrees Celsius, but what makes them useful for energy technology is their high energy, not the material temperature. In solar panels, the energy of hot electrons can be converted to electrical energy more efficiently than traditional methods.
Thermal electrons can also accelerate chemical reactions, thereby increasing the efficiency of energy technologies such as hydrogen fuel cells in automobiles.
Reddy said: "In a typical chemical reaction, the reactants need to have enough energy to cross a threshold to complete the reaction. If there are these high-energy electrons, some electrons will lose energy to the reactants, pushing them across the threshold, so that The chemical reaction speeds up."
Working with Reddy is Wang Kun, a postdoctoral fellow in the research group of Professor Edgar Mayhofer and Professor Pramod Reddy at the University of Michigan. They spent more than 18 months together developing the experimental device, and another year to measure the energy of the hot electrons.
It is reported that the researchers established a system to study the difference between the charge current and the excited and unexcited plasma conditions. Based on the key information contained in this difference in current, the energy distribution of the hot electrons in the metal nanostructure can be determined.
By irradiating the laser on a thin gold film with small bumps, a plasma is excited in this system, thereby generating hot electrons. The researchers introduced hot electrons into the gold electrode on the top of the scanning tunneling microscope and measured its energy.
This method can be used to promote various applications related to energy.
Chakrapani Varanasi, project manager of the US Army Research Service, supported the study. He said: "This multidisciplinary basic study reveals a unique way to measure the energy of charge carriers. It is estimated that these research results will play an important role in the development of future applications, such as energy conversion, photocatalysis and photodetectors, etc. Interested in these."
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