First, there were light-emitting diodes, or LEDs. Then, organic LEDs, or OLEDs. Now, researchers in the lab of Chuan Wang, assistant professor in the Preston M. Green Department of Electrical & Systems Engineering, have
developed a new material that has the best of both technologies and a novel way to fabricate it -- using an inkjet printer.
Organic LEDs, made with organic small molecules or polymer materials, are cheap and flexible. You can bend or stretch them -- but they have relatively low performance and short lifetime. Inorganic LEDs such as microLEDs are high performing, super bright and very reliable, but not flexible and very expensive.
The researchers made an organic-inorganic compound, which has the best of both worlds.
They used a particular type of crystalline material called an organometal halide perovskite, though with a novel twist. The traditional way to create a thin layer of perovskite, which is in liquid form, is to drip it onto a flat, spinning substrate, like a spin art toy, in a process known as spin coating. As the substrate spins, the liquid spreads out, eventually covering it in a thin layer.
From there, it can be recovered and made into perovskite LEDs, or PeLEDs.
Because it comes in a liquid form, the researchers imagined they could use an inkjet printer for production.
Inkjet fabrication saves materials, as the perovskite can be deposited only where it's needed, in a similar way to the precision with which letters and numbers are printed on a piece of paper; no splatter, less waste. The process is much faster as well, cutting fabrication time from more than five hours to less than 25 minutes.
The university's Office of Technology Management has a pending patent on the technology and fabrication method.
These PeLEDs may be just the first step in an electronics revolution: Walls could provide lighting or even display the day's newspaper. They can be used to make wearable devices, even smart wearables, like a pulse oximeter to measure blood oxygen.
