DOE OSTI2011
Progress over Phase II of DE-FG02-07ER86293 'Materials Degradation Analysis and Development to Enable Ultra Low Cost, Web-Processed White P-OLED for SSL' was initially rapid in terms of device performance improvements. We exceeded our device luminance lifetime goals for printed flexible white OLEDs as laid out in our project proposal. Our Phase II performance target was to demonstrate >1500 hours luminance lifetime at 100 Cd/m2 from a printed flexible device. We now have R&D devices well in excess of 8000 hrs lifetime at 100 Cd/m2, tested in air. We also were able to produce devices which met the voltage target of >1500 hours below 15V operation. After completing the initial performance milestones, we went on to focus on color-related degradation issues which were cited as important to commercialization of the technology by our manufacturing partners. We also put additional focus on cathode work as the active material development that occurred over the STTR time period required an adaptation of the cathode from the original cathode formulations which were developed based on previous generation active layer materials. We were able to improve compatibility of the cathode with some of the newer generation active layer materials and improve device yield and voltage behavior. An additional objective of the initial Phase II was to further develop the underlying manufacturing technology and real-life product specifications. This is a key requirement that must be met to ensure eventual commercialization of this DOE-funded technology. The link between commercial investment for full commercialization and R&D efforts in OLED solid State Lighting is often a large one. Add-Vision's lower cost, printed OLED manufacturing approach is an attraction, but close engagement with manufacturing partners and addressing customer specifications is a very important link. Manufacturing technology encompasses development of moisture reduction encapsulation technology, improved cost performance, and reductions in operating voltage through thinner and higher uniformity active device layers. We have now installed a pilot encapsulation system at AVI for controlled, high throughput lamination encapsulation of flexible OLEDs in a novel process. Along with this, we have developed, with our materials supply partners, adhesives, barrier films and other encapsulation materials and we are showing total air product lifetimes in the 2-4 years range from a process consistent with our throughput goals of {approx}1M device per month ({approx}30,000 sq. ft. of processed OLEDs). Within the last year of the project, we have been working to introduce the manufacturing improvements made in our LEP deposition and annealing process to our commercial partners. Based on the success of this, a pilot scale-up program was begun. During this process, Add-Vision was acquired by a strategic partner, in no small part, because of the promise of future success of the technology as evidenced by our commercial partners pilot scale-up plans. Overall, the performance, manufacturing and product work in this project has been successful. Additional analysis and device work at LBL has also shown a unique adhesion change with device bias stressing which may result from active layer polymer cross-linking during bias stressing of device. It was shown that even small bias stresses, as a fraction of a full device lifetime stress period, result in measurable chemical change in the device. Further work needs to be conducted to fully understand the chemical nature of this interaction. Elucidation of this effect would enable doped OLED formulation to be engineered to suppress this effect and further extend lifetimes and reduce voltage climb.