September 8, 2015: Flexible organic LED (OLED) is the next-generation lighting technology because it has features like color tuning, low driving voltage, large-area light emission, etc.
However, OLEDs are still inflexible despite being based on organic materials. To achieve more efficiency, flexible substrates for OLEDs should be developed. As a result, good flexible substrates, electrode materials, and encapsulation techniques compatible with these flexible substrates should be developed.
Addressing the technical challenges associated with the development of high performing flexible substrates, electrode materials compatible with these substrates and good encapsulation techniques would lead to efficient and reliable flexible OLEDs and make flexible solid-state lighting commercially feasible.
A team of researchers at Pohang (Republic of Korea) University of Science and Technology explained the advances in three key areas?flexible electrodes, flexible encapsulation methods, and flexible substrates. These make commercial use of OLED more feasible and closer to implementation.
Min-Ho Park and other researchers at Pohang tested a variety of transparent electrodes as flexible alternatives to currently available devices based on indium tin oxide (ITO), which is brittle and increasingly expensive, and identified next steps toward making flexible solid-state lighting commercially feasible:
- development of a flexible electrode that has high electrical conductivity, high bending stability, few defects, smooth surface texture, and high work function
- reduction in the water-vapor transmission rate of materials used, to counter the vulnerability of OLEDs to moisture.
The Pohang team demonstrated good electrical, optical, and mechanical performance with flexible electrodes fabricated using graphene, conducting polymers, silver nanowires (AgNWs), and dielectric-metal-dielectric (DMD) multilayer structures.
However, various obstacles still remain with these devices’ durability, conductivity, surface roughness, and fabrication cost. Current flexible substrates and encapsulation methods are being explored, with the goal of reducing cost and processing time, and increasing durability.
Source: SPIE–International Society for Optics and Photonics