Microcavity Near-Infrared OLED Electrodes With High Reflectance
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Solution Overview
Problem
In light-emitting devices with a microcavity structure, the use of high-reflectance electrode materials for visible light ranges leads to increased light absorption, reducing emission efficiency, as the thickness of semi-transmissive and semi-reflective electrodes needs to be minimized to prevent absorption losses.
Innovation Solution
Employing high-reflectance materials like gold (Au), silver (Ag), or copper (Cu) for electrodes in the near-infrared range, with specific thickness ranges to enhance reflectance while minimizing absorption, and incorporating an organic layer with a refractive index greater than 1.7 to improve light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-reflectance electrode materials are used for visible light ranges, then reflectance is improved, but light absorption increases and emission efficiency decreases
Solution Approach 1:
The patent changes the wavelength parameter from visible light to near-infrared light range, where high-reflectance materials exhibit lower absorption. It also optimizes the thickness parameter of the semi-transmissive and semi-reflective electrode to a specific range (5 nm to 20 nm) to achieve high reflectance while minimizing absorption losses in the near-infrared range
Solution Approach 2:
The patent applies different optical properties to different parts of the electrode structure. The first electrode is designed as a reflective electrode with high reflectance, while the second electrode is designed as a semi-transmissive and semi-reflective electrode with optimized thickness to balance transmission and reflection functions in the near-infrared range
2Loss of energy
If the thickness of semi-transmissive and semi-reflective electrode is reduced to prevent absorption losses, then emission efficiency is improved, but reflectance decreases
Solution Approach 1:
The patent changes the wavelength parameter to near-infrared range where high-reflectance materials have lower absorption coefficients, allowing the use of very thin electrode layers (5-20 nm) that provide high reflectance while minimizing absorption losses. This thickness optimization simultaneously achieves both high emission efficiency and high reflectance
Solution Approach 2:
The patent employs composite electrode structures combining different materials with complementary properties. High-reflectance materials such as gold, silver, or copper are used specifically for their optical properties in the near-infrared range, while optimizing the overall electrode composition to achieve both high reflectance and low absorption
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 solution results in a light-emitting device with improved emission efficiency and reduced driving voltage, maintaining high reflectance in the near-infrared range while optimizing light extraction and conductivity.
Implementation Method 1
incorporating an organic layer with a refractive index greater than 1.7 to improve light extraction efficiency
Implementation Method 2
Employing high-reflectance materials like gold (Au), silver (Ag), or copper (Cu) for electrodes in the near-infrared range, with specific thickness ranges to enhance reflectance
Implementation Method 3
voltage application between a pair of electrodes causes, in an EL layer, recombination of electrons and holes injected from the electrodes, which brings a light-emitting substance (organic compound) contained in the EL layer into an excited state, and the light-emitting substance emits light when returning to the ground state from the excited state
Data Source
AI summary
A novel light-emitting device with a microcavity structure which can improve the emission efficiency compared to the conventional one is provided. In a light-emitting device with a microcavity structure that emits light in a near-infrared range, reflectance of one or both of a first electrode (reflective electrode) and a second electrode (semi-transmissive and semi-reflective electrode) with respect to light in a near-infrared range (e.g., light with a wavelength of 850 nm) is higher than the reflectance thereof with respect to light in a visible light range (greater than or equal to 400 nm and less than 750 nm).