̽��ֱ�� of Cambridge - organic electronics

Spinning, twisted light could power next-generation electronics

sc604 — Thu, 13 Mar 2025 18:09:28 +0000

̽��ֱ��researchers, led by the ̽��ֱ�� of Cambridge and the Eindhoven ̽��ֱ�� of Technology, have created an organic semiconductor that forces electrons to move in a spiral pattern, which could improve the efficiency of OLED displays in television and smartphone screens, or power next-generation computing technologies such as spintronics and quantum computing.

̽��ֱ��semiconductor they developed emits circularly polarised light—meaning the light carries information about the ‘handedness’ of electrons. ̽��ֱ��internal structure of most inorganic semiconductors, like silicon, is symmetrical, meaning electrons move through them without any preferred direction.

However, 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.

But by using molecular design tricks inspired by nature, the researchers created a chiral semiconductor by nudging stacks of semiconducting molecules to form ordered right-handed or left-handed spiral columns. Their results are reported in the journal Science.

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. ̽��ֱ��chiral semiconductor developed by the researchers naturally emits light in a way that could reduce these losses, making screens brighter and more energy-efficient.

“When I started working with organic semiconductors, many people doubted their potential, but now they dominate display technology,” said Professor Sir Richard Friend from Cambridge’s Cavendish Laboratory, who co-led the research. “Unlike rigid inorganic semiconductors, molecular materials offer incredible flexibility—allowing us to design entirely new structures, like chiral LEDs. It’s like working with a Lego set with every kind of shape you can imagine, rather than just rectangular bricks.”

̽��ֱ��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,” said co-first author Marco Preuss, from the Eindhoven ̽��ֱ�� of Technology. “ ̽��ֱ��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 record-breaking efficiency, brightness, and polarisation levels, making them the best of their kind.

“We’ve essentially reworked the standard recipe for making OLEDs like we have in our smartphones, allowing us to trap a chiral structure within a stable, non-crystallising matrix,” said co-first author Rituparno Chowdhury, from Cambridge’s Cavendish Laboratory. “This provides a practical way to create circularly polarised LEDs, something that has long eluded the field.”

̽��ֱ��work is part of a decades-long collaboration between Friend’s research group and the group of Professor Bert Meijer from the Eindhoven ̽��ֱ�� of Technology. “This is a real breakthrough in making a chiral semiconductor,” said Meijer. “By carefully designing the molecular structure, we’ve coupled the chirality of the structure to the motion of the electrons and that’s never been done at this level before.”

̽��ֱ��chiral semiconductors represent a step forward in the world of organic semiconductors, which now support an industry worth over $60 billion (about £45 billion). 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.

̽��ֱ��research was supported in part 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. Rituparno Chowdhury is a member of Fitzwilliam College, Cambridge.

Reference

Rituparno Chowdhury, Marco D Preuss et al. ‘Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films.’ Science (2025). DOI:10.1126/science.adt3011

Researchers have advanced a decades-old challenge in the field of organic semiconductors, opening new possibilities for the future of electronics.

It’s like working with a Lego set with every kind of shape you can imagine, rather than just rectangular bricks

Richard Friend

Samarpita Sen, Rituparno Chowdhury

Confocal microscopy image of a chiral semiconductor

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Switching ‘spin’ on and off (and up and down) in quantum materials at room temperature

sc604 — Wed, 16 Aug 2023 15:00:00 +0000

Spin is the term for the intrinsic angular momentum of electrons, which is referred to as up or down. Using the up/down spin states of electrons instead of the 0 and 1 in conventional computer logic could transform the way in which computers process information. And sensors based on quantum principles could vastly improve our abilities to measure and study the world around us.

An international team of researchers, led by the ̽��ֱ�� of Cambridge, has found a way to use particles of light as a ‘switch’ that can connect and control the spin of electrons, making them behave like tiny magnets that could be used for quantum applications.

̽��ֱ��researchers designed modular molecular units connected by tiny ‘bridges’. Shining a light on these bridges allowed electrons on opposite ends of the structure to connect to each other by aligning their spin states. Even after the bridge was removed, the electrons stayed connected through their aligned spins.

This level of control over quantum properties can normally only be achieved at ultra-low temperatures. However, the Cambridge-led team has been able to control the quantum behaviour of these materials at room temperature, which opens up a new world of potential quantum applications by reliably coupling spins to photons. ̽��ֱ��results are reported in the journal Nature.

Almost all types of quantum technology – based on the strange behaviour of particles at the subatomic level – involve spin. As they move, electrons usually form stable pairs, with one electron spin up and one spin down. However, it is possible to make molecules with unpaired electrons, called radicals. Most radicals are very reactive, but with careful design of the molecule, they can be made chemically stable.

“These unpaired spins change the rules for what happens when a photon is absorbed and electrons are moved up to a higher energy level,” said first author Sebastian Gorgon, from Cambridge’s Cavendish Laboratory. “We’ve been working with systems where there is one net spin, which makes them good for light emission and making LEDs.”

Gorgon is a member of Professor Sir Richard Friend’s research group, where they have been studying radicals in organic semiconductors for light generation, and identified a stable and bright family of materials a few years ago. These materials can beat the best conventional OLEDs for red light generation.

“Using tricks developed by different fields was important,” said Dr Emrys Evans from Swansea ̽��ֱ��, who co-led the research. “ ̽��ֱ��team has significant expertise from a number of areas in physics and chemistry, such as the spin properties of electrons and how to make organic semiconductors work in LEDs. This was critical for knowing how to prepare and study these molecules in the solid state, enabling our demonstration of quantum effects at room temperature.”

Organic semiconductors are the current state-of-the-art for lighting and commercial displays, and they could be a more sustainable alternative to silicon for solar cells. However, they have not yet been widely studied for quantum applications, such as quantum computing or quantum sensing.

“We’ve now taken the next big step and linked the optical and magnetic properties of radicals in an organic semiconductor,” said Gorgon. “These new materials hold great promise for completely new applications, since we’ve been able to remove the need for ultra-cold temperatures.”

“Knowing what electron spins are doing, let alone controlling them, is not straightforward, especially at room temperature,” said Friend, who co-led the research. “But if we can control the spins, we can build some interesting and useful quantum objects.”

̽��ֱ��researchers designed a new family of materials by first determining how they wanted the electron spins to behave. Using this bottom-up approach, they were able to control the properties of the end material by using a building block method and changing the ‘bridges’ between different modules of the molecule. These bridges were made of anthracene, a type of hydrocarbon.

For their ‘mix-and-match’ molecules, the researchers attached a bright light-emitting radical to an anthracene molecule. After a photon of light is absorbed by the radical, the excitation spreads out onto the neighbouring anthracene, causing three electrons to start spinning in the same way. When a further radical group is attached to the other side of the anthracene molecules, its electron is also coupled, bringing four electrons to spin in the same direction.

“In this example, we can switch on the interaction between two electrons on opposite ends of the molecule by aligning electron spins on the bridge absorbing a photon of light,” said Gorgon. “After relaxing back, the distant electrons remember they were together even after the bridge is gone.

“In these materials we’ve designed, absorbing a photon is like turning a switch on. ̽��ֱ��fact that we can start to control these quantum objects by reliably coupling spins at room temperature could open up far more flexibility in the world of quantum technologies. There’s a huge potential here to go in lots of new directions.”

“People have spent years trying to get spins to reliably talk to each other, but by starting instead with what we want the spins to do and then the chemists can design a molecule around that, we’ve been able to get the spins to align,” said Friend. “It’s like we’ve hit the Goldilocks zone where we can tune the spin coupling between the building blocks of extended molecules.”

̽��ֱ��advance was made possible through a large international collaboration – the materials were made in China, experiments were done in Cambridge, Oxford and Germany, and theory work was done in Belgium and Spain.

̽��ֱ��research was supported in part by the European Research Council, the European Union, the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI), and the Royal Society. Richard Friend is a Fellow of St John’s College, Cambridge.

Reference:
Sebastian Gorgon et al. ‘Reversible spin-optical interface in luminescent organic radicals.’ Nature (2023). DOI: 10.1038/s41586-023-06222-1

Researchers have found a way to control the interaction of light and quantum ‘spin’ in organic semiconductors, that works even at room temperature.

These new materials hold great promise for completely new applications, since we’ve been able to remove the need for ultra-cold temperatures

Sebastian Gorgon

Artist's impression of aligned spins in an organic semiconductor

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

‘Fruitcake’ structure observed in organic polymers

sc604 — Thu, 02 Jun 2022 08:35:03 +0000

̽��ֱ��field of organic electronics has benefited from the discovery of new semiconducting polymers with molecular backbones that are resilient to twists and bends, meaning they can transport charge even if they are flexed into different shapes.

It had been assumed that these materials resemble a plate of spaghetti at the molecular scale, without any long-range order. However, an international team of researchers found that for at least one such material, there are tiny pockets of order within. These ordered pockets, just a few ten-billionths of a metre across, are stiffer than the rest of the material, giving it a ‘fruitcake’ structure with harder and softer regions.

̽��ֱ��work was led by the ̽��ֱ�� of Cambridge and Park Systems UK Limited, with KTH Stockholm in Sweden, the Universities of Namur and Mons in Belgium, and Wake Forest ̽��ֱ�� in the USA. Their results, reported in the journal Nature Communications, could be used in the development of next-generation microelectronic and bioelectronic devices.

Studying and understanding the mechanical properties of these materials at the nanoscale – a field known as nanomechanics – could help scientists fine-tune those properties and make the materials suitable for a wider range of applications.

“We know that the fabric of nature on the nanoscale isn’t uniform, but finding uniformity and order where we didn’t expect to see it was a surprise,” said Dr Deepak Venkateshvaran from Cambridge’s Cavendish Laboratory, who led the research.

̽��ֱ��researchers used an imaging technique called higher eigen mode imaging to take nanoscale pictures of the regions of order within a semiconducting polymer called indacenodithiophene-co-benzothiadiazole (C16-IDTBT). These pictures showed clearly how individual polymer chains line up next to each other in some regions of the polymer film. These regions of order are between 10 and 20 nanometres across.

“ ̽��ֱ��sensitivity of these detection methods allowed us to map out the self-organisation of polymers down to the individual molecular strands,” said co-author Dr Leszek Spalek, also from the Cavendish Laboratory. “Higher eigen mode imaging is a valuable method for characterising nanomechanical properties of materials, given the relatively easy sample preparation that is required.”

Further measurements of the stiffness of the material on the nanoscale showed that the areas where the polymers self-organised into ordered regions were harder, while the disordered regions of the material were softer. ̽��ֱ��experiments were performed in ambient conditions as opposed to an ultra-high vacuum, which had been a requirement in earlier studies.

“Organic polymers are normally studied for their applications in large area, centimetre scale, flexible electronics,” said Venkateshvaran. “Nanomechanics can augment these studies by developing an understanding of their mechanical properties at ultra-small scales with unprecedented resolutions.

“Together, the fundamental knowledge gained from both types of studies could inspire a new generation of soft microelectronic and bioelectronic devices. These futuristic devices will combine the benefits of centimetre scale flexibility, micrometre scale homogeneity, and nanometre scale electrically controlled mechanical motion of polymer chains with superior biocompatibility.”

̽��ֱ��research was funded in part by the Royal Society.

Reference:
Illia Dobryden et al. ‘Dynamic self-stabilization in the electronic and nanomechanical properties of an organic polymer semiconductor.’ Nature Communications (2022). DOI: 10.1038/s41467-022-30801-x

Researchers have analysed the properties of an organic polymer with potential applications in flexible electronics and uncovered variations in hardness at the nanoscale, the first time such a fine structure has been observed in this type of material.

Deepak Venkateshvaran

Polymer film with a region of parallel alignment of individual polymer chains

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

A new spin on organic semiconductors

sc604 — Tue, 26 Mar 2019 00:00:59 +0000

̽��ֱ��international team from the UK, Germany and the Czech Republic has found that these materials could be used for ‘spintronic’ applications, which could make cheap organic semiconductors competitive with silicon for future computing applications. ̽��ֱ��results are reported in the journal Nature Electronics.

‘Spin’ is the term for the intrinsic angular momentum of electrons, which is referred to as up or down. Using the up/down states of electrons instead of the 0 and 1 in conventional computer logic could transform the way in which computers process information.

Instead of moving packets of charge around, a device built on spintronics would transmit information using the relative spin of a series of electrons, known as a pure spin current. By eliminating the movement of charge, any such device would need less power and be less prone to overheating – removing some of the most significant obstacles to further improving computer efficiency. Spintronics could therefore give us faster, energy-efficient computers, capable of performing more complex operations than at present.

Since organic semiconductors, widely used in applications such as OLEDs, are cheaper and easier to produce than silicon, it had been thought that spintronic devices based on organic semiconductors could power a future computer revolution. But so far, it hasn’t worked out that way.

“To actually transfer information through spin, the electron’s spin needs to travel reasonable distances and live for a long enough time before the information encoded on it is randomised,” said Dr Shu-Jen Wang, a recent PhD graduate of the ̽��ֱ�� of Cambridge’s Cavendish Laboratory, and the paper’s co-first author.

“Organic semiconductors have not been realistic candidates for spintronics so far because it was impossible to move spins around a polymer circuit far enough without losing the original information,” said co-first author Dr Deepak Venkateshvaran, also from the Cavendish Laboratory. “As a result, the field of organic spintronics has been pretty quiet for the past decade.”

̽��ֱ��internal structure of organic semiconductors tends to be highly disordered, like a plate of spaghetti. As such, packets of charge don’t move nearly as fast as they do in semiconductors like silicon or gallium arsenide, both of which have a highly ordered crystalline structure. Most experiments on studying spin in organic semiconductors have found that electron spins and their charges move together, and since the charges move more slowly, the spin information doesn’t go far: typically only a few tens of nanometres.

Now, the Cambridge-led team say they have found the conditions that could enable electron spins to travel far enough for a working organic spintronic device.

̽��ֱ��researchers artificially increased the number of electrons in the materials and were able to inject a pure spin current into them using a technique called spin pumping. Highly conductive organic semiconductors, the researchers found, are governed by a new mechanism for spin transport that transforms them into excellent conductors of spin.

This mechanism essentially decouples the spin information from the charge, so that the spins are transported quickly over distances of up to a micrometre: far enough for a lab-based spintronic device.

“Organic semiconductors that have both long spin transport lengths and long spin lifetimes are promising candidates for applications in future spin-based, low energy computing, control and communications devices, a field that has been largely dominated by inorganic semiconductors to date,” said Venkateshvaran, who is also a Fellow of Selwyn College.

As a next step, the researchers intend to investigate the role that chemical composition plays in an organic semiconductor’s ability to efficiently transport spin information within prototype devices.

̽��ֱ��research was coordinated by Professor Henning Sirringhaus at the Cavendish Laboratory and funded through a European Research Council (ERC) Synergy Grant jointly held by the ̽��ֱ�� of Cambridge, Imperial College London, ̽��ֱ�� of Mainz, Czech Academy of Sciences and Hitachi Cambridge Laboratory.

Reference:
Shu-Jen Wang, Deepak Venkateshvaran et al. ‘Long spin diffusion lengths in doped conjugated polymers due to enhanced exchange coupling.’ Nature Electronics (2019). DOI: 10.1038/s41928-019-0222-5

Researchers have found that certain organic semiconducting materials can transport spin faster than they conduct charge, a phenomenon which could eventually power faster, more energy-efficient computers.

Organic semiconductors have not been realistic candidates for spintronics so far because it was impossible to move spins far enough without losing the original information

Deepak Venkateshvaran

Deepak Venkateshvaran and Nanda Venugopal

Hand sketch of an organic lateral spin pumping device

Yes