Scientists have developed a surprising new way to power normally non-conducting materials, opening the door to a new generation of ultra-pure near-infrared LEDs for medical imaging, communications technology and advanced sensors.
This breakthrough relies on tiny “molecular antennas” that focus electrical energy onto insulating nanoparticles. Researchers at the Cavendish Laboratory at the University of Cambridge used this method to create the first-ever LED from a previously “unpowerable” material.
Their discovery is nature.
Molecular antenna Power insulating nanoparticles
This research focuses on lanthanide-doped nanoparticles (LnNPs), a material known for producing highly stable and highly purified light. These are particularly valuable because they emit light in the second near-infrared region, which can penetrate deep into living tissue. This makes them attractive for medical imaging and sensing technologies.
Despite their optical advantages, these nanoparticles have one major drawback. They are electrical insulators and cannot easily conduct current through them. This limitation has prevented scientists from using them in electronic devices such as LEDs.
Researchers at the University of Cambridge have discovered a way around this obstacle, which was previously thought to be impossible under normal conditions. By attaching specially selected organic molecules to nanoparticles, the researchers created a system that can transfer electrical energy to insulating materials.
Professor Akshay Rao, who led the research at the Cavendish Laboratory, said: “These nanoparticles are amazing light emitters, but they cannot be powered by electricity, which has been a major barrier to their use in everyday technology.” “We’ve basically discovered a backdoor to power them. Organic molecules act like antennas, capturing charge carriers and ‘whispering’ them to the nanoparticles through a special triplet energy transfer process, which is surprisingly efficient.” ”
Organic hybrid LED achieves more than 98% energy transfer
To make this technology work, scientists constructed a hybrid material that combines organic molecules and inorganic nanoparticles. They attached an organic dye called 9-anthracenecarboxylic acid (9-ACA) to the surface of the LnNPs.
Inside the newly designed LED, the charge is directed to the 9-ACA molecules rather than the nanoparticles themselves. These molecules act as molecular antennas, absorbing incoming energy and entering an excited “triplet state.”
In many optical systems, triplet states are considered “dark” because they often lose energy. However, with this new design, triplet energy is transferred to the lanthanide ions within the nanoparticles with more than 98% efficiency. This process causes the insulating nanoparticles to emit bright, pure light.
Ultra-high purity near-infrared LED with low power consumption
The resulting device is called an “LnLED” and operates at a relatively low voltage of about 5 volts. They also produce electroluminescence with a very narrow spectral width, providing a much purer light output than competing technologies such as quantum dots (QDs).
“The purity of the light in the second near-infrared window emitted by our LnLEDs is a major advantage,” said the study’s lead author, Dr. Zhongzheng Yu, a postdoctoral fellow at the Cavendish Institute. “Applications such as biomedical sensing and optical communications require very sharp and specific wavelengths. Our device easily achieves this, which is very difficult to do with other materials.”
Possibilities of medical image processing and optical communication
This technology could lead to a wide range of future applications. Because LEDs emit extremely pure near-infrared light, they could enable new medical devices that can see deep inside the body.
Small, injectable or wearable LnLEDs could help doctors detect cancer, monitor organs in real time, and activate light-sensitive drugs with great precision.
Narrow, stable light emission could also improve optical communication systems by reducing interference and allowing large amounts of data to be transmitted more clearly and efficiently. Additionally, this technology has the potential to support highly sensitive detectors that can identify specific chemicals or biological markers.
First generation devices are already showing excellent results
The research team has already achieved peak external quantum efficiencies of more than 0.6% in NIR-II LEDs, an impressive result for an early-generation device. Scientists also say there is a clear path to further improving performance.
“This is just the beginning. We have unlocked a whole new class of materials for optoelectronics,” added Dr. Yunzhou Deng, a postdoctoral fellow at the Cavendish Laboratory. “The basic principle is so versatile that we can now explore countless combinations of organic molecules and insulating nanomaterials. This allows us to create devices with tailored properties for applications never before thought of.”
This research was supported in part by a UK Research and Innovation (UKRI) Frontiers Research Grant (EP/Y015584/1) and a Postdoctoral Individual Fellowship (Marie Skłodowska-Curie Fellowship Grant Scheme).
