Fabrication of Light Scattering Structure by Self-organization of a Polymer: Application to Light Out-coupling Enhancement in OLEDs

抄録

Light scattering structures for light out-coupling enhancement in organic light emitting devices (OLEDs) were fabricated by self-organization of poly[(9,9-di-n-octylfluorenyl-2,7diyl)-alt-(benzo[2,1,3]-thiadiazol-4,8-diyl)] (F8BT). The F8BT film spin-coated from chloroform or THF solution showed smooth surface, while the film spin-coated from the mixture of chloroform/1,4-dioxane or THF/1,4-dioxane solution showed rough wavy surface. Fourier transformation of the waves in the rough F8BT films exhibited large components having the wavelength corresponding to near-infrared region. Orange-emitting OLEDs were fabricated on the rough F8BT films. Indium zinc oxide (IZO) and organic layers were deposited by either evaporation or spin-coating. The surface roughnesses of the evaporated organic layers were same as the surface roughness of the F8BT. On the other hand, the spin-coated organic layer reduced the roughness of the F8BT. Both in the evaporated and the spin-coated OLEDs, the external quantum efficiencies of OLEDs were increased by 1.2 times compared with those of the OLEDs without the F8BT, indicating that the F8BT served as light scattering structure to enhance light out coupling.