This new OLED material could contain 10,000 pixels per inch in future displays

In the race to create ever brighter and more detailed displays, researchers have reached a new milestone. A new OLED architecture, based on a technology originally designed for ultra-thin solar panels, can now pack a hefty 10,000 pixels per inch (ppi), achieving a level of resolution that far exceeds that currently found in smartphones and state of the art televisions.

The result of collaboration between researchers at Stanford University and the Samsung Institute for Advanced Technology (SAIT), the technology takes advantage of a material called ‘metaphotonic’ that can control light in a new way.

Commercial OLED TVs currently have a pixel density of around 100-200ppi, while the resolution of newer smartphones is around 400-500ppi. But in addition to setting new pixel density records, new OLED displays built on the metaphotonic material could be brighter and show better color accuracy, while cost less to produce.

Organic Light Emitting Diode (OLED) displays are based on tiny organic compounds that emit light when stimulated by an electrical current. The pixels on the screen are made up of stacks of emitters, each of which produces red, green or blue light. By controlling the group of emitting diodes, therefore, it is possible to create visible colors for the human eye to see on the screen.

In OLED smartphone displays, each emitter on the screen typically produces one of the primary colors and is then applied against a sheet of metal that filters out the correct diodes to control the composition of each pixel. Television screens, on the other hand, use white OLEDs, which emit all three primary colors at once. Filters are then placed over the emitters to determine the final color of the diode, in order to produce the correct pixel.

Both methods have their shortcomings: thick metal foils applied to colored diodes limit the scale of the display, while colored filters applied to white emitters consume more power.

With these limitations in mind, SAIT scientist Won-Jae Joo found himself, a few years ago, attending a presentation by Stanford graduate student Majid Esfandyarpour on a seemingly unrelated topic: solar panel designs.

Esfandyarpour was exploring the possibility of creating new materials, called ‘metamaterials’, to manipulate light in the design of ultrathin solar cells. Joo immediately saw how the idea could be applied to OLED displays, and a partnership was soon established between Samsung and the Stanford research team.

At the heart of the new OLED architecture the researchers have unveiled is a base layer called an ‘optical metasurface’, which is made of reflective metal and dotted with microscopic pillars that together “crinkle” the layer’s surface.

These pillars, thanks to their different sizes and arrangements, can manipulate the different specific wavelengths of red, blue and green lights. When white light falls on the pillars, the pillars can, in turn, “assign” a specific primary color to the opposing diodes. In this way, different pillar patterns on the metasurface define different colors. The researchers compared the process to the sound that resonates in the cavities of a musical instrument.

Researchers have successfully produced miniature proof-of-concept pixels as part of laboratory tests using the new method, with promising results. Compared to OLEDs used in televisions, metaphotonic material allows for higher color purity and a two-fold increase in luminescence efficiency, which means the screen is brighter and uses less power.

VR and AR application

The displays could get a big quality boost, therefore, if OLED displays based on the new architecture proposed by the Stanford and Samsung researchers go into commercial production. But TV and smartphone makers won’t be the only players to benefit from the added pixel density.

“For near-eye micro-displays, for example, in virtual and augmented reality applications, the required pixel density extends to several thousand pixels per inch and cannot be achieved with current display technologies,” the researchers said. “An ultra-high density of 10,000 pixels per inch easily meets the requirements of next-generation micro-displays that can be made into glasses or contact lenses.”

For years, manufacturers of virtual reality headsets have tried to refine the quality of images to fulfill the promise of “immersive experiences.” However, with today’s displays, it cannot be said that users consistently get a compelling experience in virtual worlds.

Virtual reality headsets are placed inches from the user’s eyes, which means that high resolutions are key to creating realistic images. Therefore, the researchers are confident that the metasurfaces will provide unprecedented levels of detail that could change the industry game.

With no time to waste, Samsung is now drafting the next steps to integrate the meta-OLED proof-of-concept into a full-size display.