Flexible distributed Bragg reflectors as optical outcouplers for OLEDs based on a polymeric anode

摘要

Top-emitting OLEDs (TOLEDs) represent a promising technology for the development of next- generation flexible and rollable displays, thanks to their improved light outcoupling and their compatibility with opaque substrates. Metal thin films are the most used electrodes for the manu- facturingofTOLEDs,buttheyshowpoorresistancetomechanicaldeformation,whichcompromises the long-term durability of flexible devices. This paper reports the exploitation of a dielectric mirror (DBR) based on seven pairs of TiO 2 and SiO 2 combined with a polymeric electrode as an alternative to the bottom metal electrode in flexible TOLEDs. The DBR showed a maximum reflectivity of 99.9% at about 550nm, and a stop-band width of about 200nm. The reflectivity remained unchanged after bending and treatment with water and solvents. Green TOLED devices were fabricated on top of DBRs, and demonstrated good stability in terms of electro-optical and colorimetric charac- teristics, according to varying viewing angles. These results demonstrate that the combination of the flexible DBR with the polymeric anode is an interesting strategy for improving the durability of flexible TOLEDs for display applications, implemented on different kinds of free-standing ultra-thin substrates.