Manufacturable Corrugated Substrates for High Efficiency OLEDs

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Lead Performer: North Carolina State University – Raleigh, NC
Partners: None
DOE Total Funding: $1,137,342
Project Term: May 1, 2019 – April 30, 2021
Funding Type: SSL R&D Funding Opportunity Announcement (FOA) (DE-FOA-0001823)

Project Objective

Almost 40% of the light is trapped in an OLED as the waveguided (WG) modes as well as the surface plasmon polariton (SPP) modes, and corrugated substrates are effective to extract this light. Specifically, random corrugated structures are especially ideal for this purpose, because the extracted light profile will be independent of wavelength and angle. Previous DOE-funded research conducted by the team shows that an ideal corrugated structure for light extraction should have an optimized corrugated depth at the metal electrode interface to extract the SPP modes, and a large refractive contrast at the transparent electrode interface to extract the WG modes. To realize OLEDs for general lighting, the researchers will fabricate white OLEDs on random corrugated substrates having an optimized nanostructure and a large index contrast at the ITO interface. The objective is threefold: to develop a continuous roll-to-roll process to produce corrugated substrates that are compatible with large-volume manufacturing; to fabricate OLEDs on random corrugated substrates with a large index contrast at the ITO/substrate interface (Δn ≥ 0.7) to extract the light lost to the SPP modes, and with an optimized corrugated depth to extract the WG modes; and to collaborate with an OLED manufacturer to validate the resulting devices. Previous results show that the team can achieve an external quantum efficiency of 72% in its corrugated green OLEDs. By incorporating a low-index buffer layer on top of a random corrugated glass substrate to enhance the refractive index contrast, preliminary results show that an extraction efficiency of 75% is an achievable target for a fully optimized white OLED.

Project Impact

Manufacturable substrates for high-efficiency light extraction are one of the major roadblocks for OLED lighting, and the success of this program will definitely accelerate its commercialization process, because the process developed will be ready to be transferred to an OLED lighting manufacturer.  

Contacts

DOE Technology Manager: Brian Walker, brian.walker@ee.doe.gov  
Lead Performer: Franky So, North Carolina State University