Enhanced light extraction efficiency and viewing angle characteristics of microcavity OLEDs by using a diffusion layer

Abstract

The viewing angle characteristics and light extraction efficiency of organic light-emitting diodes (OLEDs) with a micro-cavity structure were enhanced. This was accomplished by inserting a diffusion layer composed of nano-sized structures of a transparent polymer poly(methyl methacrylate) (PMMA) combined with a zinc oxide (ZnO) semi-planarization layer with a high refractive index (n = 2.1) into the devices. The PMMA nanostructures were fabricated by employing a reactive ion etching (RIE) process. The height and density of the PMMA nanostructures were controlled by varying the speed at which the PMMA was spin-coated onto the substrate. The insertion of the diffusion layer into the micro-cavity OLEDs (MC-OLEDs) improved the external quantum efficiency (EQE) by as much as 17% when compared to that of a MC-OLED without a diffusion layer. Furthermore, adjustment of the viewing angle from 0° to 60° halved the peak shift distance of the electroluminescence (EL) spectra from 42 to 20 nm. Additionally, changing the viewing angle from 0° to 60° changed the color coordinate movement distance of the MC-OLED with the diffusion layer to 0.078, less than half of the distance of the MC-OLED without the diffusion layer (0.165).

Design of Monolithic Bi-Layer High-Z PAL-Si Hard X-ray CMOS Image Sensors for Quantum Efficiency Enhancement

“…To this end, experiments were conducted to assess the performances of five Si CIS configurations that varied according to whether the device included a high-Z PAL, 250 nm Bi 2 Te 3 , a lower-Z substitution material, 500 nm Sn, a conventional scintillator material, L 2 Y 2 SiO 5 (LYSO) [23,24], and incidentally, a PMMA window. While high-Z PAL-CIS has been experimentally verified as a powerful tool to enhance QE compared to Si direct detection, another necessary verification was to determine whether coupling high-Z PAL with conventional state-of-the-art scintillator materials such as LYSO or materials that have been proven to assist with a light extraction efficiency enhancement would help with further increase in QE [25][26][27]. The specifications for each of the five treatments in the follow-up study are tabulated in Table 6.…”

Selective Enhancement of Viewing Angle Characteristics and Light Extraction Efficiency of Blue Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes through an Easily Tailorable Si3N4 Nanofiber Structure

“…While the IQE of TADF OLEDs can theoretically reach 100%, the external quantum efficiency (EQE) struggles to exceed 20%. − This limitation is attributed to several modes, such as substrate mode and waveguide mode, resulting from refractive index differences between the interfaces within the OLED and surface plasmon polariton modes generated at the interface between the metal and organic layers. − Various structural solutions have been proposed to address these issues and analyze the improvement in OLED performance, such as tuning the thickness or material of the layers ,− and the incorporation of light extraction layers, such as nanostructured materials or microlens arrays (MLAs). ,− Given the stability and efficiency challenges associated with blue TADF organic materials, studies on light extraction structures applicable to blue TADF OLEDs hold significant value.…”

Pulsed Laser Deposition of Transparent Conductive Oxides on UV-NIL Patterned Substrates for Optoelectronic Applications

“…In this way, almost 30% of the emitted photons are trapped in the glass substrate (glass mode), while a 50% are trapped at the organic/anode interface (waveguide mode). Therefore, various methods were used to extract more efficiently the light from the OLEDs [9,13].…”