Ultrastable Glass Layers Improve OLED Performance

Researchers demonstrated that it is possible to use ultrastable film formation to improve the performance of OLEDs. Emission layers of OLEDs were grown as ultrastable glasses, a growth condition that allowed for the most thermodynamically stable molecular conformation that can be achieved in amorphous solids.

OLEDs with four different phosphorescent emitters showed a greater than 15 percent enhancement in efficiency and operational stability, said the research team from Technische Universität Dresden and Universitat Autònoma de Barcelona. According to the team, the increase in OLED performance (efficiency and device lifetime) correlated to the glass transition temperature.

Researchers noted that the concept of incorporating ultrastable glass layers was independent of the emitter technology used, so OLEDs based on any high-performance emitter types could equally benefit from the new approach, if the emitter orientation was not hampered at the respective substrate temperature.

Improving OLEDS on the nanoscale. Courtesy of Joan Rafols Ribé (UA Barcelona) and Paul Anton Will (TU Dresden).

Researchers also noted that these improvements were achieved not by refining materials, nor by changing the device architecture — the current paths to improvement in OLED technology. Thus, the new approach to improving OLED performance could have general applicability to any OLED stack, regardless of the materials used. The team noted that, in particular, its approach could be useful for improving the performance of thermally activated delayed fluorescence (TADF) OLEDs. Performance enhancements made using ultrastable glass layers would be made in addition to any advances in material development, the current driver for improvement.

The team believes that future research will need to investigate material and device properties that could potentiallly counteract the observed effects of the glass. Also, the influence of the material deposition conditions on the charge carrier transport of organic small molecules must be correlated to solely excitonic effects for a complete understanding of the approach to be achieved.

Beyond the OLED technology platform, the formation of organic ultrastable glasses has the potential to further increase the performance of various organic electronic devices and systems, said the team.

The research was published in Science Advances (doi:10.1126/sciadv.aar8332).