Improvement of Colour Gamut in Bottom-Emission Organic Light-Emitting Diodes Using Micro-Cavity Structure Embedded Cathodes

Abstract

We demonstrate an approach for improving the colour gamut of bottom-emission organic light-emitting diodes (OLEDs) through micro-cavity structure embedded cathodes. The devices with micro-cavity structure embedded cathodes showed an improved colour gamut of 91.5% (National Television System Committee (NTSC)), 95.8% (Adobe RGB), and 129.2% (sRGB), compared to those of the devices without micro-cavity structure embedded cathodes—59.2% (NTSC), 62.0% (Adobe RGB), 83.6% (sRGB). In addition, the performance of red, green, and blue devices are also investigated depending on the optical length of the micro-cavity structure.

Novel Zinc Complex with an Ethylenediamine Schiff Base for High-Luminance Blue Fluorescent OLED Applications

“…6−8 Moreover, wide EL spectra of such materials frequently do not meet the requirements of color purity. 9 Among the most promising organic emitters that demonstrate state-of-the-art lighting characteristics within deep-blue fluorescent OLEDs, one can mention Lee's naphthyl-linked phenanthroimidazole−carbazole hybrid species (external quantum efficiency, EQE max = 6.6%), 10 C6-and C9-substituted phenanthro [9,10-d]imidazoles (EQE max = 5.8%), 11 and 1,2-bis(4′-(1-phenyl-1-H-benzo[d]imidazole-2yl)-[1,1′-biphenyl]-4-yl)-1H-phenanthro [9,10-d] imidazole (EQE = 4.1%), 12 Jayabharathi's twisted dihydrobenzodioxin phenanthroimidazole derivatives (EQE max = 5.3%), 13 and Yang's metalinked donor−acceptor triphenylamine-phenanthroimidazole species (EQE max = 3.3%) 14 and 4-[2-(4′diphenylamino-biphenyl-4-yl)-phenanthro [9,10-d]imidazole-1yl]-benzonitrile (EQE max = 7.8%). 15 Very recently, Pal et al 16,17 have published very interesting utilization of roomtemperature columnar pure organic liquid crystals for the fabrication of blue OLEDs with the highest EQE of 4.0%.…”

“…It is well known that a general target for OLED investigations is to develop full-color displays and solid-state lighting (SSL) sources. Despite the significant progress achieved in this field in the last decade, the production of blue monochromatic materials that can be used as active emissive layers in OLEDs remains an important problem that, so far, has hampered the production of a complete white electroluminescence (EL) involving a balanced simultaneous emission of the three primary colors of light. − The implementation of such blue emitters in displays and SSL technologies are limited due to low lifetime and a high roll-off efficiency in the electroluminescent devices. − Moreover, wide EL spectra of such materials frequently do not meet the requirements of color purity . Among the most promising organic emitters that demonstrate state-of-the-art lighting characteristics within deep-blue fluorescent OLEDs, one can mention Lee’s naphthyl-linked phenanthroimidazole–carbazole hybrid species (external quantum efficiency, EQE max = 6.6%), C6- and C9-substituted phenanthro­[9,10- d ]­imidazoles (EQE max = 5.8%), and 1,2-bis­(4′-(1-phenyl-1- H -benzo­[ d ]­imidazole-2-yl)-[1,1′-biphenyl]-4-yl)-1 H -phenanthro­[9,10- d ] imidazole (EQE = 4.1%), Jayabharathi’s twisted dihydrobenzodioxin phenanthroimidazole derivatives (EQE max = 5.3%), and Yang’s metalinked donor–acceptor triphenylamine-phenanthroimidazole species (EQE max = 3.3%) and 4-[2-(4′-diphenylamino-biphenyl-4-yl)-phenanthro­[9,10- d ]­imidazole-1-yl]-benzonitrile (EQE max = 7.8%) .…”

Device Characteristics of Top-Emitting Organic Light-Emitting Diodes Depending on Anode Materials for CMOS-Based OLED Microdisplays

“…Each device exhibited slightly different EL emission peaks and full-width-at-half-maxima (FWHM), owing to their different micro-cavity effect. Micro-cavity effect typically consists of the Fabry-Perot factor and the two-beam interference factor [23], [24]. These two factors are determined by the micro-cavity length, the reflectance value at the electrode-organic interface, the refractive index of materials, phase changes at the electrode-organic interface, the transmittance of semi-transparent electrode, and the location of the emission zone from the organic/reflective metal electrode interface.…”

Non-toxic near-infrared light-emitting diodes

“…Microcavity structures are a viable strategy to improve the color gamut, tailor the emission, and enhance light extraction from visible OLEDs ( Lee et al., 2018 ; Thomschke et al., 2012 ; Chien et al., 2016 ; Grüner et al., 1996a ). In traditional Fabry-Pérot microcavity architectures, the EML is generally sandwiched between a reflective electrode and a semitransparent electrode ( Park et al., 2014 ).…”