German University Develops World's Smallest OLED Pixel

Physicists at Julius-Maximilians-Universitt Würzburg (JMU) in Germany have successfully developed the world's smallest OLED light-emitting pixel, which can be used in micro-display applications. The relevant research results have been published in the academic journal Science Advances.

Wearable display technologies, such as smart glasses and invisible display devices, are considered important future developments. However, due to optical limitations and luminous efficiency, the manufacturing of micro-display technology has always been a challenge in the industry. Traditional optical principles dictate that when pixel size is reduced to an order of magnitude comparable to the wavelength of light, luminous efficiency will drop significantly, making it difficult to maintain display brightness.

To address this, the research team at the University of Würzburg innovatively introduced an "optical antenna" structure and utilized a special metal contact layer to achieve the dual functions of current injection and light amplification. This allowed them to create pixels emitting orange light in an area of just 300 x 300 nanometers, with a brightness comparable to that of conventional OLED pixels measuring 5 x 5 micrometers. This means that a display with a 1920 x 1080 resolution could theoretically be compressed into an area of just one square millimeter.

The research team noted that the key to this achievement lies in a breakthrough in structural design. OLEDs consist of multiple layers of organic thin films sandwiched between two electrodes. When current flows through them, electrons and holes recombine, stimulating the organic molecules to emit light. Because each pixel is self-luminous, eliminating the need for a backlight, they achieve high contrast, vibrant colors, and high energy efficiency, making them ideal for AR and VR devices.

However, traditional OLEDs suffer from uneven current distribution during the miniaturization process. If the structure is directly reduced, the current will be concentrated in the corners of the pixel, which not only leads to uneven light emission, but may also cause the migration of gold atoms due to the strong electric field, forming a filament structure and causing a short circuit, ultimately destroying the pixel.

To address this issue, the research team added a special insulating layer on top of the optical antenna, leaving only a circular hole with a diameter of approximately 200 nanometers in the center, effectively preventing current from being injected from the edges. This design significantly improved the stability of the pixel, allowing it to operate stably for more than two weeks in natural environments.

The research team stated that the current luminous efficiency of this nano-OLED pixel is approximately 1%. The team will next focus on further improving this efficiency and expanding the luminous range to include the full red, green, and blue color range. If the research proceeds successfully, it is expected that a micro-display system with a complete full-color display will be realized in the future.