Organic Electroluminescent Device Microcavity Light Out-Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic electroluminescent devices suffer from low light escape efficiency due to scattering, internal reflection, and absorption, leading to reduced image quality and color purity, and face challenges in achieving intense, narrow band-width emission.
Innovation Solution
The implementation of a microcavity structure between the substrate and the second electrode, with optimized layer thicknesses to enhance light out-coupling and maintain electrical properties, is proposed, where the distance between the substrate and the second electrode is set to [(¼ni)λ+(½nj)aλ]±40 nm, with ni and nj being average refractive indices, to maximize reflection and transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional layer structures are used in organic electroluminescent devices, then the device structure is simple, but light escape efficiency is low due to scattering, internal reflection, and absorption
Solution Approach 1:
The device is divided into multiple functional layers with specific thicknesses: the light-emissive layer is segmented into 50-100 nm thickness, the hole transport layer into 10-30 nm, and the electron transport layer into 10-30 nm. This segmentation allows optimization of light out-coupling at each interface while maintaining overall structural simplicity
Solution Approach 2:
The patent optimizes specific parameter ranges for each layer thickness to enhance light escape efficiency. By controlling the light-emissive layer thickness at 50-100 nm and transport layers at 10-30 nm, the device achieves improved opto-electrical efficiency without significantly complicating the structure
2Loss of energy
If layer thicknesses are optimized to enhance light out-coupling, then opto-electrical efficiency increases, but electrical properties may be adversely affected
Solution Approach 1:
The patent identifies optimal parameter ranges that simultaneously satisfy optical and electrical requirements. The light-emissive layer thickness of 50-100 nm optimizes light out-coupling while maintaining charge transport, and the transport layers at 10-30 nm ensure proper charge injection without compromising electrical performance
Solution Approach 2:
Different layers are assigned specific thickness optimizations tailored to their local functions: the light-emissive layer (50-100 nm) is optimized for light generation and out-coupling, while the transport layers (10-30 nm) are optimized for charge transport. This local quality approach ensures both optical efficiency and electrical reliability are maintained in their respective regions
3Illumination intensity
If conventional emission is used, then the device structure is simple, but color purity is poor and image quality is reduced
Solution Approach 1:
The patent optimizes layer thickness parameters to enhance emission intensity and narrow bandwidth. The light-emissive layer thickness of 50-100 nm and transport layers of 10-30 nm are specifically tuned to improve color purity and emission characteristics without adding complex structural elements
Solution Approach 2:
The patent converts the typically harmful effects of scattering and internal reflection into beneficial microcavity effects by optimizing layer thicknesses. The light-emissive layer and transport layers are designed to create constructive interference for desired wavelengths, enhancing color purity and emission intensity while eliminating the need for additional optical components
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
This configuration significantly increases the opto-electrical efficiency of the device, improves color purity, and extends the device's lifetime by optimizing light out-coupling without altering the emission color, allowing for a more efficient and longer-lasting organic electroluminescent device.
Implementation Method 1
a microcavity is formed between the substrate and the second electrode, the distance between the transparent substrate and the second electrode being [(1⁄4ni)λ+(1⁄2nj)aλ]±40 nm
Implementation Method 2
the second electrode is reflective... to maximize reflection and transmittance
Implementation Method 3
the first electrode is transparent or semi-transparent... to maximize reflection and transmittance
Implementation Method 4
an organic light-emissive layer disposed between the first and the second electrode for emitting light of a wavelength λ from a recombination zone within the light-emissive region
Data Source
AI summary
An organic electroluminescent device comprising: a transparent substrate; a first electrode; a second reflective electrode and an organic light-emitting region for emitting light of a wavelength 1 from a recombination zone within the light-emissive region, and a microcavity formed between the substrate and the second electrode, the distance between the transparent substrate and the second electrode being [(¼ni)l+(½nj)al]±40 nm, where a is zero or a positive integer, ni is an average refractive index of the material disposed between the recombination zone and the second electrode and nj is an average refractive index of the material disposed between the recombination zone and the substrate.