According to the latest news from the University of Würzburg in Germany, a team of physicists from the school has successfully developed the world's smallest light-emitting pixel, bringing a breakthrough to ultra-miniature displays for wearable devices such as smart glasses. As one of the key future technologies that can project digital information directly into the user's field of vision, smart glasses' development is restricted by the volume limitations of display components and optical performance bottlenecks. Previously, when the pixel size was reduced to only one wavelength, the effective emission efficiency of light has been difficult to break through.
A research team from the University of Würzburg has created the smallest light-emitting pixels ever created by using optical antenna technology. The research was led by Professors Jens Pflaum and Bert Hecht and has been published in the journal Science Advances. The researchers said that by combining metal electrodes with organic light-emitting diodes, they successfully lit an orange light pixel in an area of only 300 nanometers × 300 nanometers, and its brightness was comparable to that of conventional-sized (5 micron × 5 micron) OLED pixels. For example, a 1920×1080 resolution display screen material can be fully integrated into an area of 1 square millimeter and can be used in eyeglass frames to project light onto the lenses for display.
The core of OLED display is composed of multiple layers of ultra-thin organic materials sandwiched between two electrodes. After electricity is applied, electrons and holes recombine in the active layer, exciting organic molecules to release energy to form photons. Each pixel can emit light independently without the need for a backlight, helping to deliver deeper blacks, vivid colors, and improved energy-efficiency management of portable devices in the field of virtual reality and augmented reality devices.
The researchers pointed out that simply shrinking traditional OLED pixels cannot solve the technical bottleneck of miniaturization. Due to the uneven distribution of current at extremely small sizes, such as the lightning rod effect, the current is mainly concentrated in the corners of the antenna, thereby forming metal "filaments" in the optically active material, which can easily lead to short-circuit failure over time.
The new structure developed by the team adds a special insulating layer to the top of the optical antenna, leaving only an opening with a diameter of 200 nanometers in the center. In this way, the current from the corners is effectively shielded, ensuring the reliable and stable operation of the nanophotodiode and preventing the generation of filaments. Experiments show that the first batch of nanopixels can work stably for two weeks under normal conditions.
In the next step, the team plans to improve the pixel luminous efficiency (currently 1%), expand the color gamut to cover the full spectrum of RGB, and strive to achieve large-scale application of micro-displays. This new technology is expected to make displays and projection equipment extremely small and invisible and integrated into various wearable devices - including glasses and even contact lenses.
Compiled from /ScitechDaily