SmartKem claims to have created the world’s first monolithic micro-LED display using organic thin-film transistors (OTFTs). The company believes that its method of processing a thin-film transistor backplane on top of Gallium Nitride LEDs has the potential to accelerate the commercialization of microLED displays, which promise higher brightness, lower power consumption and longer lifetime. MicroLEDs are considered particularly important for portable powered displays such as smartwatches and AR/VR displays.
Existing efforts at establishing micro-LED manufacturing use physical transfer of LEDs from the wafer upon which they are manufactured to the TFT display backplane, where they must be laser welded to the contact pad of the transistor to make an electrical connection. Since, for high resolution displays, millions of tiny LEDs need to be transferred from one place to another, then the potential for placement error is large. If a 99.9% placement yield is achieved, then a full HD color display will have over 6,000 faulty sub-pixel LEDs that would need to be identified, removed, and re-attached. Once the 6,000 faulty LEDs have been replaced, a 99.9% yield will still mean six of these will be faulty. It is the process of seeking out the faults and then replacing them one by one which is slowing down commercialization.
SmartKem’s patented core chemistry allows its semiconductor inks to be processed at the low temperature of 80°C, allowing the company to process its transistors directly on top of the micro-LEDs. This eliminates the mass transfer and laser welding processes, and the fabrication of OTFTs can use existing low-cost manufacturing tools currently used for LCD backplane manufacturing. This approach cannot be carried out with other types of thin-film transistors as they are processed at the much higher temperature of 300°C, which damages the microLEDs, and is why you need to make them separately and then laboriously join them together one by one.
In 2022, had been doing tests and had demonstrated technology that can drive miniLEDs using active matrix (AM) manufacturing processes used by existing LCD panels. However, the company had also started to look at how its materials could be used to drive microLEDs. This seems to be the result of work that had got the company noticed then and should continue to see it evolve to do greater things.
