OLED Light Extraction Structure Using High-Index Nanoparticles
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Solution Overview
Problem
OLED devices suffer from inefficient light out-coupling due to trapped photons in the planar waveguide, leading to low light transmission efficiency and high internal quantum efficiency without effective extraction into useful directions.
Innovation Solution
Incorporation of a light diffracting substructure with high index nanoparticles and a planarization layer, arranged between a transparent substrate and an anode, to enhance light scattering and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar waveguide structure is used in OLED, then the device structure is simple and easy to manufacture, but light transmission efficiency is low due to trapped photons
Solution Approach 1:
The patent introduces a light diffracting substructure with specific refractive index parameters (ns≥1.9, np within 25% of na) to change the optical parameters of the OLED system. This enables efficient light extraction by creating refractive index contrast that facilitates photon escape from the waveguide, resolving the contradiction between simple structure and low light transmission efficiency
Solution Approach 2:
The patent employs a composite light diffracting substructure consisting of multiple layers with different refractive indices (substrate, nanoparticles with ns≥1.9, and planarization layer with np). This composite structure combines materials with specific optical properties to achieve both ease of manufacture and high light transmission efficiency through controlled light scattering and extraction
2Productivity
If high index nanoparticles are introduced to improve light extraction, then light extraction efficiency increases, but device complexity increases
Solution Approach 1:
The patent applies local quality by introducing light diffracting properties only in the substructure layer, rather than modifying the entire OLED. The nanoparticles and planarization layer are localized to the light extraction interface, providing the necessary optical complexity only where needed while keeping the rest of the device simple and manufacturable
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 achieves a 2.5× to 3× increase in out-coupling efficiency and maintains low signal loss, with a light extraction efficiency of at least 40%, utilizing simple manufacturing processes.
Implementation Method 1
a light diffracting substructure providing a scattering cross section of light from the diode superstructure
Implementation Method 2
a plurality of nanoparticles in contact with the substrate and having a refractive index of ns
Data Source
AI summary
An organic light emitting diode (OLED) assembly (100), comprising: a diode superstructure (110) comprising a cathode (140), an anode (120) having a refractive index of na, and an organic light emitting semiconductor material (160) interposed between the cathode (140) and the anode (120); and a light diffracting substructure (150) providing a scattering cross section of light from the diode superstructure (110). The light diffracting substructure (150) comprises: a transparent substrate (156), a plurality of nanoparticles (154) in contact with the substrate (156) and having a refractive index of ns, and a planarization layer (152) over the nanoparticles (154) and having a refractive index of np. Further, np is within 25% of na and ns>np In addition, ns> about 1.9.