Island-like random scattering layer for light extraction in organic light-emitting diodes with enhanced luminous efficiencies and angular spectral stability

Optical outcoupling efficiency of organic light-emitting diode (OLED) can be improved using nanoscale or sub-micrometer quasi-periodic structures. An embossed nano/micro-structure inserted between the substrate and anode is known to be effective in extracting the waveguide mode. However, the techniques to fabricate these nanoscale or sub-micrometer structures are usually complicated, and the light extraction is wavelength-oriented. Herein, we develop a simple process to enhance the performance of OLED. We texture the glass surface with shrinking Ag droplets in the form of island structures and then deposit SiNx planarization film to form an island-like random scattering layer (IRSL), which changes the light path of emitting light in a way to reduce light attenuation and extract emission outward. Furthermore, IRSL has a low haze and a high optical transparency, both of which are beneficial to light output. The OLEDs constructed with IRSL as an internal light extraction structure exhibit a significant improvement of current and power efficiencies by 52% and 62%, respectively, compared to the planar OLED device. In addition, compared to the conventional pillar-structured RSL, the IRSL not only facilitates the extraction of light for a broad range of visible light region, but also favors better angular spectral stability and Lambertian emission.