Cd-free Quantum Dot Color Converters for MicroLED Applications

MicroLED technology is poised to disrupt the display market by bringing a whole new value proposition to consumers products. Flexible, high brightness and excellent lifetime are but a few keywords to describe a new generation of displays spanning virtual reality to wearable applications. To date, challenges in scaling pick-and-place processes and in producing highly efficient red and green native microLEDs hamper microLED mass production. A quantum dot (QD) color conversion strategy to produce an RGB display from an array of blue microLEDs is an elegant way to simplify the manufacturing process and to overcome several technological challenges in the mass-transfer process, the display brightness and the driving electronics.
Quantum dots have earned their place as down-convertors for displays since the commercialization of Cd-based QDs in LCDs in the early 2010’s and the commercialization of QD-OLED almost a decade later. The benefits in terms of color quality and conversion efficiency are widely recognized as key selling points. A shift towards greener, Cd-free materials has been initiated by European RoHS directives that restrict the use of Cd in consumer appliances. This stimulated the development of InP- based QDs, which can nowadays be produced through economical synthesis routes and with excellent optical properties.
The successful application of RoHS-compliant QDs for microLED combines challenging requirements in terms of absorption, solid loading, conversion efficiency and photostability. Over the years, we have developed on-chip grade and RoHS-compliant QDs that can showcase the viability of InP-based QDs for microLED applications. We will discuss our progress on red and green QDs towards relevant film thicknesses and light intensities.