A research team at the University of Minnesota has manufactured the first 3D-printed OLED display. This flexible display measures 3.8 cm by 3.8 cm and has 65 pixels. This could be the start of lightweight, cost-effective, foldable TV screens.

OLEDs rely on organic materials to emit light, unlike crystalline semiconductors for LCDs. What makes them more attractive is that they do not require backlighting and are more energy efficient. OLEDs also have a wider viewing angle and are more resistant to breakage. 3D printing these diodes presents its fair share of challenges; creating the organic layer that converts electricity to light is difficult because of the need for consistency. Also, polymer-metal bonding through 3D printing is generally unstable.

Multiple layers for one small OLED

The small, flexible OLED was created with six layers and two different 3D printers at the University of Minnesota. The first layer was a flexible PET film combined with silver nanoparticles and the fourth was silicone. The final layer was secured with a polymer cast.

“Overall, the lack of uniformity in the active layers caused large variations in light emission across the active regions within the same batch of devices, signifying the need for alternatives to extrusion printing for the fabrication of large-scale display devices. Therefore, we exploited a spray printing method to deposit MDMO-PPV to improve the uniformity of the active layers. The spray nozzle was integrated into our printing system, whereby the ink was atomized at the orifice when a high relative speed was created between the near-static ink and the pressurized sheath gas. The atomized droplets had diameters in the range of 30 to 50 μm and rapidly evaporated after impacting the substrate, resulting in suppressed mass transport in the lateral direction. In the spray-printed active region, microdroplets were uniformly distributed across the target area and a substantial reduction in the thickness variation was observed,” a research team member explained.

The machine used to create this 3D-printed OLED was custom created for the task. The full abstract can be viewed here.