It seems I’ve written a lot recently about EL-QLED progress, even though commercialization would appear to be still many years off. But it is just so interesting I can’t help myself! You may recall I lamented about the status of blue EL-QLED (electroluminescent QLED) earlier this year in Singing the EL-QLED Blues. A recent article in Nature by the team at SAIT has demonstrated some phenomenal progress in blue EL-QLED which has me a little less melancholy. Add to this Nanosys’ reported progress in green EL-QLED at SID Display Week 2020, and the outlook could be described as… promising.
First let me set the stage. Progress in EL-QLED has been consistently slow for Cd-free EL-QLED. Particularly in terms of stability under operating conditions. Samsung’s own Changhee Lee presented a brief historical summary last month at SPIE Optics and Photonics. What is missing from this graph however are two data points that were just recently released (if you are impatient you can scroll down to my revised graphic).
In the Nature paper, Samsung describes the multitude of chemical and processing changes they make in order to achieve these metrics. Highlights include:
• Synthesis of cubic ZnTeSe/ZnSe/ZnS QDs optimized Te content for 457 nm emission
• Reduced imperfections (stacking faults) in QD by treatment with HF and ZnCl2 during shell growth
• Elimination of trap states by treating QDs with ZnCl2 after synthesis (in solution and film form factors)
• Improved charge balance by tuning electronics of the QD bands via treatment with chloride salt
• Double emissive QD layer with different surface treatments