Dr. Jeroen Vleggaar Builds Some Custom OLED Displays — Using a 3D Printer as a Lithography Tool

Turning a 3D printer into a photolithographic tool gives it a whole new flexibility — and allows for home-designed OLED panels.

Gareth Halfacree
3 years agoDisplays / 3D Printing

Optics specialist Dr. Jeroen Vleggaar has published a video showcasing precisely what goes into making organic light-emitting diode (OLED) display panels — by making some himself, using a 3D printer as a lithographic tool.

"In my first real job, I worked as a researcher at Philips Research on polymer LED technology," Vleggaar explains. "That was back in the 90s and back then, I made a lot devices in all kinds of shapes and sizes and colors. So, I guess this video is a bit of a walk down memory lane. But it is also a test to see if I still have what it takes to make a good OLED."

Some glass, some chemicals, a few tools, and a few decades of experience, and you too can build OLED panels. (📹: Huygens Optics)

Vleggaar's video begins with a history of organic LEDs, which spun out of research on organic solar cells carried out by Ching W. Tang in the 1980s. "By the way, the name 'organic' does not mean that the materials used occur in nature," he points out. "It just refers to the fact that they are hydrocarbon based."

With the theory down, Vleggaar turns to construction of two devices: A seven-segment display and one with a fixed text — or image — which glows. "To make these, I had to do some photolithography first and I decided to use a simple resin 3D printer as the exposure tool for this," he explains.

"With a pixel resolution of 35 microns, it allows for easy but fairly low-resolution patterning of resist layers. The 3D printer normally uses the LEDs of 405nm to cure the different resin layers in a 3d print. But of course, you can also use that light to expose a photoresist."

Using spin-coated glass substrates with ITO layers already applied, Vleggaar exposed the devices using custom STL files — but, obviously, no resin in the vat - and then baked them at before developing in a dilute sodium hydroxide solution and etching with 30 per cent hydrochloric acid.

The next steps involved physical vapor deposition, placing materials — including ytterbium and Alq3 — also known by its somewhat more length chemical name tris(8-hydroxyquinolinato)aluminium, and a key component of lightweight OLED devices.

While impressively functional, Vleggaar's OLEDs are unlikely to be long-lived. "Even after being in air for about 30 minutes, the devices still look pretty acceptable, at least with the naked eye. But if you look under a microscope, you can already see degradation setting in," he says during the video.

"It proceeds mainly by formation of black spots, which grow gradually in time. These black spots form because oxygen and water diffuse into the device though pinholes in the cathode layer. And these pinholes are actually very difficult to avoid, unless you work in a very high-class clean-room environment."

The full video is available on Vleggaar's YouTube channel, Huygens Optics.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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