The research team successfully engineered an organic semiconductor that directs electrons in a helical trajectory, a development with the potential to significantly improve the energy efficiency of television and smartphone screens. This semiconductor generates circularly polarised light, enabling it to convey information regarding electron spin-a feature that could revolutionize electronic devices.
Conventional inorganic semiconductors, including silicon, have symmetrical internal structures, allowing electrons to travel without any preferred direction. However, many natural molecules exhibit chirality, meaning they have distinct left- or right-handed configurations, much like human hands. Although chirality is fundamental to biological functions such as DNA formation, leveraging it in electronics has been a formidable challenge.
Inspired by nature's molecular structures, the researchers devised a technique to prompt stacks of semiconducting molecules to self-organize into either left- or right-handed spiral columns. Their findings, published in *Science*, demonstrate the successful fabrication of a chiral semiconductor.
One promising application of this discovery lies in display technology. Current screens suffer significant energy losses due to inefficient light filtration. The newly developed chiral semiconductor naturally emits circularly polarised light, potentially minimizing these inefficiencies and yielding brighter, more energy-efficient screens.
"When I started working with organic semiconductors, skepticism was widespread, but today they dominate the display industry," said Professor Sir Richard Friend from Cambridge's Cavendish Laboratory, a co-leader of the study. "Unlike rigid inorganic semiconductors, molecular materials offer extraordinary adaptability, enabling us to construct novel architectures such as chiral LEDs. It's akin to building with an unlimited variety of Lego pieces rather than just rectangular bricks."
The innovative semiconductor is derived from triazatruxene (TAT), a material that spontaneously assembles into a helical formation. This structure allows electrons to spiral along the material, similar to a screw's thread.
"When exposed to blue or ultraviolet light, self-assembled TAT emits intensely bright green light with strong circular polarisation-an effect that has been elusive in semiconductors until now," explained Marco Preuss, co-first author from Eindhoven University of Technology. "The molecular arrangement of TAT facilitates efficient electron motion while simultaneously influencing light emission."
The research team adapted OLED fabrication techniques to integrate TAT into functional circularly polarised OLEDs (CP-OLEDs), achieving record-breaking efficiency, brightness, and polarisation levels-establishing these devices as the most advanced of their kind to date.
"We fundamentally altered the standard OLED production process, enabling us to embed a chiral structure within a stable, non-crystallising matrix," said co-first author Rituparno Chowdhury from Cambridge's Cavendish Laboratory. "This breakthrough offers a viable path to manufacturing circularly polarised LEDs, a long-standing challenge in the field."
This advancement is the product of decades of collaboration between Friend's research team and the research group of Professor Bert Meijer at Eindhoven University of Technology. "This achievement represents a major leap forward in chiral semiconductor development," noted Meijer. "By meticulously designing the molecular architecture, we have successfully linked the chirality of the structure with electron movement-something never before accomplished at this scale."
Beyond display technology, the impact of this research extends to quantum computing and spintronics, a field focused on exploiting the spin properties of electrons to enhance information storage and processing. These innovations could lead to faster, more secure computing systems.
This study was partially funded by the European Union's Marie Curie Training Network and the European Research Council. Richard Friend is a Fellow of St John's College, Cambridge, and Rituparno Chowdhury is affiliated with Fitzwilliam College, Cambridge.
Research Report:Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films
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