As part of a joint project, Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP and Sefar AG, devised a roll-to-roll processed, large-area flexible OLED. Large area OLED lighting is attractive for numerous applications in residential, architectural and automotive lighting. However, questions about efficacy, lifetime, and the cost of fabricating have made such lighting too costly to mass produce.
Sefar previously created high conductive, transparent and flexible electrode substrates that reportedly enable large area homogenous lighting. Fraunhofer FEP demonstrated such large area OLED lighting fabricated using a roll-to-roll (R2R) process.
OLEDs allow new forms designs (large area, flexible, lightweight and thin). Fraunhofer FEP says that OLEDs are one of the closest light sources to natural light and have a low energy consumption.
“The new electrode substrate SEFAR TCS Planar is manufactured in a roll-to-roll process,” explained Roland Steim, project manager at Sefar, “It is a foil like substrate with a very high conductivity of up to 0.01 Ohm/Square and a transparency above 87%. This outstanding high conductivity originates from embedded metallic wires with a diameter of currently 40 µm.”
Sefar asserts that its these metal wires decrease resistive losses in the transparent electrode substrate. Sefar further says that this decrease in resistive losses supports the development of larger and more homogeneous lighting solutions compared to conventional substrates such as pure ITO. In addition, the embedded metallic wires are less brittle in bending than the thick ITO layers on films.
According to Sefar, it was able to overcome the challenge of making the surface as smooth as possible while particular parts of the metallic wires emerge on the surface as the electrical contact to the OLED.
Stefan Mogck, head of department roll-to-roll organic technology at Fraunhofer FEP summarized its use of roll-to-roll technology in the development. “We processed the OLED in vacuum in a roll-to-roll process on SEFAR TCS Planar substrates with a specifically developed drying process and barrier film lamination. Altogether we deposited the OLED 30 m in length and 30 cm in width and OLED size up to 250 cm².”