With Semiconductor Quantum Dots, Metallic Magic is forging a dream material

With Semiconductor Quantum Dots, Metallic Magic is forging a dream material ...

The RIKEN Center for Emergent Matter Science and colleagues have successfully constructed a quantum dots superlattice that can behave similarly to a metal. The new material's conductivity was found to be one million times greater than existing quantum dot displays, although the quantum confinement of individual dots remained.

Scientists have developed a semiconductor quantum dots superlattice that acts like a metal, a significant step forward in harnessing quantum dots' full potential. This breakthrough might revolutionize quantum dot technology, such as in electroluminescence devices, thermoelectric devices, and sensors.

Researchers from the RIKEN Center for Emergent Matter Science and collaborators have successfully constructed a "superlattice" of semiconductor quantum dots that can act as a metal, potentially granting new capabilities to this popular class of materials.

Due to their distinctive optical properties, semiconducting colloidal quantum dots have received great interest in the field of medicine. They are used in solar cells, where they can increase the efficiency of energy conversion, biological imaging, and quantum computing, where they can capture and manipulate individual electrons.

The absence of orientational order in assemblies has hampered their full use. According to Satria Zulkarnaen Bisri, the lead researcher on the project, "making them metallic would enable, for example, quantum dot displays that are brighter yet less energy efficient than current devices."

The group has developed a superlattice of colloidal quantum dots with the aid of Bisri and Yoshihiro Iwasa of RIKEN CEMS, which displays the electrical conducting capabilities of a metal.

The main difficulty in achieving this was to get the individual quantum dots in the lattice to connect directly to one another, "epitaxially," without ligands, and to do this with their facets oriented in a precise manner.

As they increased the carrier density using an electric-double-layer transistor, the researchers discovered that at a certain point the individual quantum dots became one million times more conductive than what is currently available from quantum dot displays. Importantly, the quantum confinement of the individual quantum dots was still maintained, meaning that they did not lose their functionality.

"Semiconductor quantum dots have always shown promise for their optical properties, but their electronic mobility has been a challenge," says Iwasa. "Our research has demonstrated that precise orientation control of the quantum dots in the assembly can lead to high electronic mobility and metallic behavior."

According to Bisri, "We intend to conduct further studies with this class of materials, and believe it will lead to significant improvements in quantum dot superlattices' performance." This may include truly all-QD direct electroluminescence devices, electrically driven lasers, thermoelectric devices, and high-sensitivity detectors and sensors, which previously were beyond the scope of quantum dot materials."

Nature Communications, 26 May 2023, Reference: "Enabling Metallic Behaviour in Two-Dimensional Semiconductor Colloidal Quantum Dots"

Researchers from the Tokyo Institute of Technology, the University of Tokyo, SPRING-8, and the Tokyo University of Agriculture and Technology were part of the project.

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