Enhanced light outcoupling from OLEDs by suppressing guided modes formation using an ultrathin flexible transparent conductor

摘要

All previous waveguide mode decoupling methods used to increase external quantum efficiency (EQE) and power efficiency of OLEDs are complex in structure and not scalable in fabrication. Here, we introduce a novel yet simple approach of using an ultrathin (~ 5 nm) copper-seeded silver (Cu-Ag) film to completely eliminate waveguide modes and enhance outcoupling efficiency of OLEDs. We experimentally verified waveguide mode elimination in the organic waveguides using index matching fluid and prism. In essence, the OLED structure can be designed to below the cutoff thickness of waveguide modes using the ultrathin Cu- Ag electrode, leading to a theoretical maximum EQE of 76.1% without compromising other characteristics of OLEDs. This EQE is higher than any other theoretically expected values reported previously without increasing fabrication steps/complexity.