Enhanced Light Extraction from Organic Light Emitting Diodes by Micrometer-Sized Buckles

Abstract

The simple ways for creating buckled structures to enhance the light extraction from OLED devices have been investigated. The buckling instability was observed when the ITO was deposited on the polymer-coated glass by sputtering. The textured surface of the ITO layer after buckling was characterized by an atomic force microscopy. The wavelength of the resulting buckled structure was a few microns in a size. The buckling was easily modified by adjusting the pressure of the argon gas during the sputter deposition of ITO layer. The buckled ITO layer was used for fabricating OLED devices. The reduction in the operating voltage for the OLED with the buckled ITO anode was observed. The current and power efficiencies for the OLED with the buckeld structure were 5% and 44% higher than those for the conventional OLED. The broader light distribution was observed in the OLED with buckling when the angular dependence of the light intensity was measured.

Hole Transport Layer Microroughening for Waveguide Mode Extraction in Organic Light‐Emitting Diodes

“…On the other hand, random scattering methods typically have much less pronounced dependence on a wavelength and directionality and generally considered to be cheaper in realization for large-scale substrates. Several methods of forming random scattering media inside OLED structure have been reported, including insertion of a thin layer dielectric nanoparticles, [11,12] spontaneously formed buckled layers, [13][14][15][16][17] embossing of random nanostructures, [18] bottom-emitting process by sublimated visible parylene dimers film, [19] and microroughening of the substrate on which the OLED stack is deposited. [20] Rough layers and substrate surface in such structures may negatively affect the lifetime of the fabricated OLEDs due to potential electrical short formed at the edge/tip of high aspect ratio random features.…”