Researchers from the Hong Kong University of Science and Technology (HKUST) School of Engineering say they have invented the world’s brightest and most energy-efficient quantum rod LEDs (QRLEDs).
Designed to maximize energy efficiency while delivering highly bright, deep green emissions “at the top of the color triangle,” these potentially breakthrough QRLEDs could replace organic LEDs (OLEDs) and quantum dot LEDs (QLEDs), and even in-development phosphorescent light emitting diodes (PHOLEDS), as the state-of-the-art LED architecture for smartphones, Televisions, and AR/VR devices by offering unprecedented color purity and a maximized color gamut.
In a statement announcing the breakthrough design, team leader Professor Abhishek K. Srivastava said their QRLED “paves the way for high-resolution, energy-efficient displays with unprecedented brightness and longevity.”
Digital displays used in smartphones and other electronic devices generate images using Light Emitting Diodes (LEDs). As resolution and display capacity have evolved, engineers have countered with more advanced LED designs, including OLEDs and QLEDs. Along with increased energy efficiency, these new LED designs also offer improved color purity and narrower emission bandwidths compared to traditional designs.
More recently, scientists have explored further improving the performance of these designs with QRLEDs. According to the research team behind the newest version, QRLEDs, which use a narrower quantum rod design than quantum dot designs, offer higher light coupling efficiency than the best OLEDs and QLEDs. This increased efficiency makes them brighter and clearer than their predecessors.
However, the research team says most incarnations “face challenges.” For example, QRLEDs’ green emission underperforms compared to quantum dot LEDS “due to inefficient charge injection, electron leakage at interfaces, and structural barriers.” These include thick insulating shells and long organic ligands, which are molecules attached to the outer surface of a nanorod that “hinder charge transport and stability.”
Curious if current QRLED designs could be improved to reduce or eliminate these shortcomings without sacrificing the benefits, Prof. Srivastava’s team designed an all-new QRLED structure. According to the team’s statement, this entirely new class of green-emitting quantum rods features a “customized core-gradient alloy structure with minimized outer shell thickness.” The researchers say the design improvements help their QRLEDs achieve “highly bright deep green emission” between 515 and 525 nanometers, which is “at the peak” of the so-called color triangle. The result is a maximized display color gamut that outperforms all previous LED designs.
To enable dense, void-free film packing, the team engineered the quantum rods at the heart of the new LEDs to have a shorter, uniform, and smooth morphology. To boost efficiency and stability, the QRLEDs also feature shorter ligands and a bilayer hole transport layer, collectively enhancing charge balance and suppressing electron leakage.
After designing their new QRLEDs, the team tested their performance and efficiency. According to their study, the new designs turned electricity into light with 24% external quantum efficiency compared to 22% for older models.
When tested for brightness per energy, the team said their new model produced 89 candela per ampere. This level of brightness per unit of energy is higher than all existing QRLEDs. The new designs also shone three times brighter than older green LEDS. According to the study, the new model achieved a tested luminescence “exceeding 500,000 cd m².”
Finally, the research team stated that their new QRLED design demonstrated operational stability of 22,000 hours. They said this level of durability positions their design for commercial display applications.
“We have successfully developed remarkably efficient and bright green-emitting QRLEDs by precisely designing the quantum rod composition, morphology, shape, and ligand structure, alongside the rational engineering of the device’s hole transport layer,” Prof. Srivastava said.
“Our work demonstrates that meticulous control over nanorod composition and interface engineering can lead to disruptive advances in optoelectronic performance.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.