A team of physicists in Germany has fabricated the smallest light-emitting pixel ever created, a breakthrough that could dramatically accelerate the development of next-generation wearable displays. The new pixel is a square measuring just 300 by 300 nanometers, yet it shines with the same brightness as conventional components many times its size. This vast reduction in scale could enable ultra-high-resolution projectors and displays small enough to be integrated seamlessly into the frames of smart glasses.
The research, conducted at Julius-Maximilians-Universität Würzburg (JMU), overcomes a fundamental barrier in optics that has long hindered the miniaturization of display technology. As pixels shrink to the size of the wavelength of light they emit, they become inefficient. The JMU team, led by Professors Jens Pflaum and Bert Hecht, circumvented this problem by designing a novel structure that functions as both a metallic contact and an optical antenna. Published in the journal Science Advances, their work paves the way for displays so dense that a full high-definition screen could fit onto an area of just one square millimeter.
Overcoming Miniaturization Barriers
For years, the goal of creating compact, high-resolution displays for augmented reality and other wearable technologies has been hampered by the physical limitations of light emission at the nanoscale. Standard organic light-emitting diodes (OLEDs), the technology common in smartphones and televisions, lose their efficiency when shrunk to sub-wavelength dimensions. The Würzburg physicists identified a key challenge related to the electrical contacts used to power these tiny pixels. In traditional designs, shrinking the pixel would cause electrical currents to concentrate at the sharp corners of the metallic contacts, similar to how a lightning rod attracts electrical charges.
This concentration of current would generate powerful electric fields, ultimately destroying the pixel. According to Professor Pflaum, the forces would be so strong that gold atoms from the contact would migrate into the light-emitting organic material, forming tiny filaments that cause a short circuit. To solve this, the researchers engineered a more robust and stable structure. Their design incorporates a specially crafted insulation layer that prevents the degradation and migration of the gold atoms, ensuring the pixel can operate without destroying itself. This innovation was critical to achieving a stable and functional pixel at such an unprecedentedly small scale.
The Optical Antenna Innovation
The core of the team’s success lies in a dual-purpose component that acts as both an electrical contact and an optical antenna. This structure, made of gold, is shaped into a cuboid with dimensions of 300 by 300 by 50 nanometers. It is designed to efficiently inject electrical current into the stack of ultra-thin organic layers that make up the OLED. When electricity passes through these layers, it excites the molecules, causing them to generate light.
Simultaneously, the metallic structure serves as an antenna that captures this generated light and radiates it outward with high efficiency. This antenna effect is what allows the nano-pixel to achieve a brightness comparable to that of a conventional OLED pixel measuring 5 by 5 micrometers—an area hundreds of times larger. This clever combination of electrical injection and light amplification within a single nano-component is what sidesteps the optical constraints that previously made such small pixels impractical.
Implications for Future Displays
The creation of such a small and bright pixel opens a new frontier for display technology, particularly for wearable devices. The researchers calculate that a full 1920 by 1080 pixel high-definition display could be constructed on a surface just one millimeter square. A display this small could be easily embedded into the arm of a pair of eyeglasses, projecting a crisp, bright image directly onto the lens without the need for bulky or cumbersome hardware that has limited the adoption of smart glasses.
Beyond smart glasses, this technology could revolutionize other fields requiring microscopic light sources or ultra-high-resolution imaging. Virtual reality goggles could offer vastly more immersive and detailed experiences, eliminating the “screen door” effect where the gaps between pixels are visible. In scientific and medical imaging, arrays of these nano-pixels could be used for advanced microscopy or as precise light sources for activating light-sensitive materials in biological research. The ability to control light at this scale provides a powerful new tool for engineers and scientists across multiple disciplines.
Current Limitations and Next Steps
While this achievement represents a major leap forward, the technology is still in its early stages. The current prototype pixel is only capable of producing orange light. For the technology to be viable for full-color displays, the researchers must develop pixels that can emit red, green, and blue light, the three primary colors that form the basis of the RGB spectrum. The team is actively working on expanding the color gamut to cover this range.
Another significant hurdle is the pixel’s efficiency. At present, the device converts only about one percent of the electrical energy it consumes into light. Improving this energy efficiency will be crucial for practical applications, especially in battery-powered mobile devices where power consumption is a primary concern. However, because the technology is based on OLEDs, it does not require a backlight, which offers an inherent efficiency advantage over LCDs. The scientists are confident that further refinements to the antenna design and the organic materials will lead to substantial improvements in efficiency. There is no firm timeline for commercialization, but the fundamental breakthrough has cleared a path for continued development.
