Narrow bridges

Building a Bandgap Fills a Performance Gap – News

A new 2D polycrystalline material incorporates fast electrical conductivity with a bandgap, promising new optoelectronic devices.

Chemical structure, graphical representation and photograph of the research team’s apparatus.
Hyuk-Jun No 2022

A flat extended lattice of molecular rings joined into larger, interconnected rings offers new electronic properties that can now be explored for useful applications.

The development comes from a research team in South Korea working with materials scientist Javeed Mahmood of King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

This innovation is part of the growing effort to develop and exploit 2D materials made up of atomic-thick layers, or a few such layers, spanning relatively wide in two dimensions.

“Devices using [our material] because the active layers exhibit remarkable performance, indicating vast potential for applications in thin-film optoelectronic devices,” says Mahmood. Optoelectronics interconverts optical and electrical signals in applications such as sensors, communication devices, and new forms of computing.

The stimulus for exploring new 2D materials stems from limitations in the electrical properties of graphene, the best-known structure of its kind, which is composed of many linked rings of six carbon atoms. Graphene suffers from limitations in electrical conduction and the ability to control conduction, which makes it unsuitable for most optoelectronics and semiconductor applications.

The new “fused aromatic network” (FAN) material incorporates nitrogen atoms into many of its six-atom rings, these rings being connected into larger rings, which are themselves all interconnected through a large molecular network dish. This structure allows rapid transport of electrons – the essential characteristic of an electric current – ​​but also incorporates an appropriate and vital aspect of semiconductor materials called the band gap. This means that a specific amount of energy is required to kick the electrons into their conducting state, allowing the precise control and turning on and off of current essential for microelectronics and optoelectronics applications.

Chemist Ali Coskun of the University of Friborg in Switzerland, who was not involved in the research, comments: “This work represents a significant advance towards understanding charge transport behavior in two-dimensional porous organic semiconductors and will certainly open up new applications. However, it is still a great challenge to synthesize large-area, defect-free films of these materials.”

Mahmood says the team plans to take on this challenge with the ultimate goal of making single crystals large enough for any working device.