Scientists have been investigating ways to improve the field of organic semiconductors. This has led to the creation of an organic semiconductor that forces electrons to move in a spiral pattern.
The aim is to improve the efficiency of OLED displays in television and smartphone screens, or to power next-generation computing technologies such as spintronics and quantum computing.
The research comes from the University of Cambridge and the semiconductor they have developed emits circularly polarised light. This is where the light carries information about the electrons.
The internal structure of most inorganic semiconductors, such as silicon, is symmetrical, meaning electrons move through them without any preferred direction.
In nature molecules often have a chiral (left- or right-handed) structure: like human hands, chiral molecules are mirror images of one another. Chirality plays an important role in biological processes like DNA formation, but it is a difficult phenomenon to harness and control in electronics.
By deploying the molecular design tricks inspired by nature, the scientists were able to create a chiral semiconductor by nudging stacks of semiconducting molecules to form ordered right-handed or left-handed spiral columns.
One promising application for chiral semiconductors is in display technology. Current displays often waste a significant amount of energy due to the way screens filter light. The chiral semiconductor developed by the researchers naturally emits light in a way that could reduce these losses, making screens brighter and more energy-efficient.
The semiconductor is based on a material called triazatruxene (TAT) that self-assembles into a helical stack, allowing electrons to spiral along its structure, like the thread of a screw.
When excited by blue or ultraviolet light, self-assembled TAT emits bright green light with strong circular polarisation — an effect that has been difficult to achieve in semiconductors until now. The structure of TAT allows electrons to move efficiently while affecting how light is emitted.
By modifying OLED fabrication techniques, the researchers successfully incorporated TAT into working circularly polarised OLEDs (CP-OLEDs). These devices showed good efficiency, brightness, and polarisation levels, making them the best of their kind.
The chiral semiconductors represent a step forward in the world of organic semiconductors. Beyond displays, this development also has implications for quantum computing and spintronics — a field of research that uses the spin, or inherent angular momentum, of electrons to store and process information, potentially leading to faster and more secure computing systems.
The research has been published in the journal Science, titled “Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films.”
