JJ Kim, J Lee, SP Yang, HG Kim, HS Kweon, SH Yoo… – Nano Letters, 2016
Courtship signals of many animal species have highly conspicuous traits for successful mating. Fireflies utilize their bioluminescent light as visual courtship signals. In addition to bioluminescent light emission, firefly’s structural role to extract the light from its lantern also drives conspicuous optical signaling. Recently, ultrastructures of firefly lanterns have become of much interest and inspired highly efficient light management. Here we report the unique optical function of hierarchical ultrastructures found in a firefly (Pyrocoelia rufa) and further the biological inspiration for highly efficient organic light-emitting diode applications. The hierarchical structures comprise longitudinal nanostructures and asymmetric microstructures, which were successfully mimicked by using geometry-guided resist reflow, replica molding, and PDMS oxidation. The external quantum efficiency (EQE) of bio-inspired OLEDs is enhanced up to 61 %. The bio-inspired OLEDs clearly show side-enhanced super-Lambertian emission with a wide-viewing angle. Highly efficient light extraction and wide-angle illumination exhibit the hierarchical structures improve the recognition of optical courtship signals in a wide-angle range. Furthermore, this biological inspiration provides a new paradigm for designing functional optical surfaces in lighting or display applications.
… calibrated spectral response Si photodiode (FDS-100-CAL, Thorlabs) and a fiber-optic spectrometer (BLUE-Wave, StellarNet, Inc.), both of which were held on a motorized goniometric arm for full angle-resolved characterizations. …
