부산대학교 도서관

Since the first demonstration of 1000cd/m2 at 1V driving voltage multilayer device by C.W. Tang in 1987, the Organic light-emitting diodes (OLEDs) have attracted attention owing to their superior properties such as flexibility or stretchability, thin thickness, self-luminous characteristic, wide color gamut, infinite contrast ratio, and fast response time. Due to these characteristics, as the attention to OLEDs increases in the display and lighting markets, the efforts on the increase of OLEDs efficiency has been performed. Nowdays, the internal quantum efficiency(IQE) of OLEDs theoretically reached almost 100% by developing phosphorescent materials and thermally activated delayed fluorescent materials. However, the external quantum efficiency of OLEDs is about 20% and the remaining about 80% light is confined inside and lost. because surface plasmon polariton(SPP) modes at between metal and organic interface, and the light is trapped in the organic/ITO layer and substrate waveguide mode in glass cause of light loss. Therefore, recently many light extraction techniques have been investigated to improve out-coupling efficiency. The light extraction technology can be classified as external light extraction and internal light extraction technology. Among the external light extraction technologies, Microlens array(MLA) is effective in substrate mode light extraction, but it has the cons of the narrow viewing angle characteristics and complex and high-cost process. Thus, in this study, we focus on decreasing the substrate waveguide mode with a simple process. This thesis suggests a simple method for fabricated the SnOx random nanoislands scattering layer to improve the light extraction of OLEDs. Sn metal is spontaneously dewetted on the glass substrate during deposition. SnOx nanoislands which induce light scattering can be easily fabricated by thermal annealing oxidation process after Sn deposition. Specifically, we focused on varying the diameter of the SnOx nanostructure to control optical characteristics. The diameter size of SnOx nanostructure enables controlled by Sn deposition thickness and located on the outside OLEDs glass substrate. The optimal diameter of SnOx nanoislands scattering layer is observed by diffuse transmittance. As a result, we demonstrated that enhancement in the EQE of OLEDs was improved by 27 % using of the optimal diameter SnOx random nanoislands scattering layer and the viewing angle shows comparable to Lambertian distribution compared with the reference one.