Organic EL Device with Multi-Interface Interference Filter
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Solution Overview
Problem
Existing organic electroluminescence (EL) devices face limitations in increasing color gamut and reducing viewing-angle dependency of luminance and chromaticity, as described in Japanese Unexamined Patent Application Publication No. 2011-159432, which focuses on flattening interference filter characteristics but lacks measures to further enhance color gamut.
Innovation Solution
A light-emitting device with a configuration that includes a first, second, and third reflective interface, and a fourth reflective interface, where the optical distances and phase shifts between these interfaces are optimized to form an interference filter with increased light transmittance in specific wavelength regions, allowing for enhanced color gamut and reduced viewing-angle dependency by satisfying specific expressions related to optical distances and phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stacked structure with multiple light-emitting layers is used, then luminous efficiency and emission lifetime are improved, but viewing-angle dependency of luminance and chromaticity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the optical distances L11, L21, L12, L22, L13, and L23 between reflective interfaces and luminescent centers, along with selecting specific central wavelengths λ1 and λ2 for different light-emitting layers. These parameter optimizations enable the interference filter to achieve flattened characteristics across wide wavelength regions, reducing viewing-angle dependency while maintaining the stacked structure's reliability benefits
Solution Approach 2:
The patent introduces another dimension by adding multiple reflective interfaces (first, second, and third reflective interfaces) at different positions within the device structure. This creates a multi-dimensional interference filter system that controls light extraction in various wavelength regions simultaneously, addressing viewing-angle dependency across the entire visible spectrum rather than at single wavelengths
2Loss of energy
If reflective interfaces are added to improve light extraction, then luminous efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing reflective interfaces that serve multiple functions simultaneously: the first reflective interface extracts blue light while the second and third interfaces extract green and red light. This multi-functional approach improves luminous efficiency across the entire visible spectrum without proportionally increasing device complexity, as each interface handles multiple wavelength regions
Solution Approach 2:
The patent merges the functions of multiple light-emitting layers (blue, green, and red emitting layers) into a single stacked structure with integrated reflective interfaces. This combining approach allows simultaneous light extraction from all layers through a coordinated interference filter system, improving overall luminous efficiency while maintaining structural compactness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optimized configuration results in a more flat light transmittance curve across a wide wavelength region, increasing color gamut and significantly reducing the viewing-angle dependency of luminance and chromaticity for light of single or combined colors in the visible wavelength region, leading to improved display performance with superior hue and low power consumption.
Implementation Method 1
a first reflective interface which is provided on the side of the first electrode so as to reflect light emitted from the first light-emitting layer and the second light-emitting layer to be emitted from the side of the second electrode
Implementation Method 2
an attempt to improve the luminous efficiency of the organic EL device using light interference in a device structure has been made
Data Source
AI summary
A light-emitting device includes: a first electrode; a second electrode; and an organic layer that is provided between the first electrode and the second electrode and is formed by stacking a first light-emitting layer and a second light-emitting layer in order from the first electrode side, in which light emitted from the organic layer is reflected by an interface between the first light-emitting layer and the first electrode, passes through the second electrode, and is emitted to the outside of the light-emitting device, a first light-transmitting layer, a second light-transmitting layer, and a third light-transmitting layer are provided on a side of the second light-emitting layer opposite to the first light-emitting layer in order from the second light-emitting layer side, and predetermined conditions are satisfied.