title: Biologically Inspired Organic Light-Emitting Diodes.
abstract: Many animal species employ highly conspicuous traits as courtship signals for successful mating. Fireflies utilize their bioluminescent light as visual courtship signals. In addition to efficient bioluminescent light emission, the structural components of the firefly lantern also contribute to the enhancement of conspicuous optical signaling. Recently, these firefly lantern ultrastructures have attracted much interest and inspired highly efficient light management approaches. Here we report on the unique optical function of the hierarchical ultrastructures found in a firefly (Pyrocoelia rufa) and their biological inspiration of highly efficient organic light-emitting diode (OLED) applications. The hierarchical structures are comprised of longitudinal nanostructures and asymmetric microstructures, which were successfully replicated using geometry-guided resist reflow, replica molding, and polydimethylsiloxane (PDMS) oxidation. The external quantum efficiency (EQE) of the bioinspired OLEDs was enhanced by up to 61%. The bioinspired OLEDs clearly showed side-enhanced super-Lambertian emission with a wide-viewing angle. The highly efficient light extraction and wide-angle illumination suggest how the hierarchical structures likely improve the recognition of firefly optical courtship signals over a wide-angle range. At the same time, the biologically inspired designs provide a new paradigm for designing functional optical surfaces for lighting or display applications.
authors.affiliation: Department of Bio and Brain Engineering and KAIST Institute for Optical Science and Technology, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Jae-Jun
authors.initials: JJ
authors.lastname: Kim
authors.affiliation: Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Jaeho
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Bio and Brain Engineering and KAIST Institute for Optical Science and Technology, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Sung-Pyo
authors.initials: SP
authors.lastname: Yang
authors.affiliation: Muju Agricultural Technology Center, 416 Hanpungnu-ro, Muju-gun, Jeonbuk 568-802, Republic of Korea.
authors.forename: Ha Gon
authors.initials: HG
authors.lastname: Kim
authors.affiliation: Division of Electron Microscopic Research, Korea Basic Science Institute , 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Hee-Seok
authors.initials: HS
authors.lastname: Kweon
authors.affiliation: Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Seunghyup
authors.initials: S
authors.lastname: Yoo
authors.affiliation: Department of Bio and Brain Engineering and KAIST Institute for Optical Science and Technology, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Ki-Hun
authors.initials: KH
authors.lastname: Jeong
keywords: Biomimetics; firefly light organs; hierarchical structures; organic light-emitting diodes; photonic structures