Role of Electron Transport Materials in Diodes

In the conventional sense, a diode is an electronic component comprising two terminals which asymmetrically conduct a current. This means that the electricity flowing through the element moves primarily in one direction. Since the onset of semiconductor electronics, most diodes have been fabricated using a junction of both positive-type and negative-type silicon, although additional materials are increasingly used. The working principle of this so-called p-n junction is determined by solid-state physics; most notably carrier mobility. In the realm of advanced diodes (OLEDs, etc.), this property can be manipulated and optimized using electron and electron-hole transport materials.

In this blog post, Avantama will explore the concept of carrier mobility with respect to the role of electron transport materials in new diode technologies.

Electron Transport Materials: Understanding P-N Recombination

Understanding electron transport materials requires a base understanding of charge carrier transport and semiconductor doping. A p-type semiconductor has a large concentration of holes and a deficit of electrons, while n-types are the inverse. When these materials are used in tandem with an applied external voltage, they will carry a unidirectional charge.

At the interface between the p-type and n-type semiconductors in a p-n junction exists a depletion region, which is an insulating area depleted of mobile charge carriers. This is generated by electronic recombination when the p-n junction is first created. As electrons diffuse from the n-type to the p-type semiconductor, they recombine to form electron-hole pairs. In their wake, these recombined units cause a charge differential between the two distinct regions of the p-n junction and an insulating region between the two. This can be overcome by ensuring that external voltages oppose the built-in potential of this insulating region.

Balancing Current with Electron Transport Materials

Electron transport materials have emerged as an ideal solution to the challenges of interface engineering and current optimization in modern diodes. They selectively allow electrons to move through an interface while blocking holes and can assist in the elimination of leak currents to increase diode performance. Ideal electron transport materials have extremely high electron densities and exceptional conductivity under operating temperatures.

In a previous blog post outlining electron transport materials, we introduced zinc oxide (ZnO) as an outstanding electron transport material due to its conductivity. Hall effect tests have shown that zinc oxide has a free electron density of approximately 10¹⁵ cm^-3 at room temperature, which goes some way to explaining the material’s success in facilitating charge mobility. This is critical in optimizing current diode technologies and enabling new technologies like innovative OLEDs and quantum dot (QD) lighting systems.

Electron Transport Materials from Avantama

Avantama is one of the world’s leading manufacturers and distributors of electronic materials for advanced applications. We provide a suite of electron transport materials for various end-product architectures and deposition techniques.

If you would like to learn more about our full product range, simply contact a member of the Avantama team today.