A new theory offers the first explanation for how electrical currents move throughout nanocrystals. The nanocrystal model developed by ETH researchers. (Image credit: ETH)


Researchers at ETH Zurich recently made a groundbreaking discovery about semiconductors made of nanocrystals. Theoretical understanding of how electrical current moves through nanocrystals eluded researchers up until now. The team has hit upon the first theoretical explanation for how electrical current is conducted in semiconductors made of nanocrystals.


The method for how electric currents travel through semiconductors is well known. The electronic properties of semiconductors can be controlled by adding impurity atoms, which changes the number of electrons. However, semiconductors made of small nanocrystal quantum dots can’t change with these methods. Whereas currents move smoothly through typical semiconductors, currents sink and deform in nanocrystal material. Due to this, the team had to change how they looked at the atoms in the crystal lattice of the nanocrystal semiconductor


Researchers ran a complex code using the Swiss Supercomputing Center CSCS in Lugano to get a better understanding of how these charges move between nanocrystals and what prevents them from moving further. The results showed how material made of many nanocrystals conducts electrical current are small deformations of crystals that cause a huge change in electrostatic energy. The current flows through polarons – when a charge deforms the material around it – causing it to hop from one nanocrystal to the next.


The team then tested the theory using thin films of nanocrystal produced in the laboratory and measured the electric response for different applied voltages and temperatures. They created free electrons at one end of the material using a short laser pulse and noted when they arrived at the other end. The computer simulation accurately predicted the electrical properties during each test.


These results could be used to develop semiconductors from nanocrystals materials for various applications in sensors, lasers, or LEDs. These materials could lead to a much broader variety of electrical properties than normal semiconductors.


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