Nonperiodic Nanostructure for OLED Light Extraction
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Solution Overview
Problem
Conventional organic light emitting devices suffer from low light extraction efficiency due to the high refractive index of organic materials and electrodes, leading to significant light wastage through total reflection and optical waveguide modes, with subwavelength photonic crystals only improving efficiency within specific wavelength ranges and causing color changes with viewing angle.
Innovation Solution
The implementation of an organic light emitting device with a nanostructure featuring nonperiodic uneven fine patterns between a substrate and electrodes, which enhances light extraction by scattering light outward and maintaining its color homogeneity, preventing diffraction patterns and color changes with viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If subwavelength photonic crystal structures are used to increase light extraction efficiency, then light extraction efficiency is improved, but color change occurs with viewing angle
Solution Approach 1:
The patent applies asymmetry by transitioning from periodic photonic crystal structures to nonperiodic uneven fine patterns. The nonperiodic arrangement of protrusions or recesses with varying sizes and spacing breaks the symmetry that causes diffraction and color separation, while still providing effective light scattering to improve extraction efficiency across all viewing angles
Solution Approach 2:
The patent implements local quality by creating regions with different refractive indices through the nonperiodic uneven fine patterns. The protrusions or recesses are distributed with varying local densities and sizes, providing position-dependent light scattering properties that collectively improve extraction efficiency without causing global color separation
2Loss of energy
If periodic photonic crystal structures are used, then light extraction efficiency is improved in specific wavelength range, but diffraction patterns and color separation occur
Solution Approach 1:
The patent eliminates diffraction patterns by replacing periodic structures with nonperiodic arrangements. The irregular spacing and varying sizes of protrusions or recesses prevent the formation of constructive interference patterns that cause diffraction, while maintaining effective light scattering for improved extraction efficiency
Solution Approach 2:
The patent uses a simpler nonperiodic pattern structure that can be manufactured more easily than complex periodic photonic crystals. The nonperiodic patterns can be formed using straightforward lithography and etching processes, reducing manufacturing complexity while achieving the desired optical performance
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 approach significantly improves the external quantum efficiency of organic light emitting devices by effectively extracting light wasted through total reflection and waveguide modes, maintaining color homogeneity and preventing color separation, thus enhancing the overall light extraction efficiency and emission pattern homogeneity.
Implementation Method 1
nanostructures, each having a nonperiodic uneven fine pattern, are formed between a substrate and a first electrode, so that the light wasted by total reflection and optical waveguide mode is extracted outwards
Implementation Method 2
it has an optical waveguide structure therein. Thus, owing to the high refractive index of an organic material and an electrode, large portion of the light emitted from an organic material layer is wasted
Data Source
AI summary
An organic light emitting device enables improvement on the loss of optical extraction efficiency due to total reflection and optical waveguide effects. The organic light emitting device has a structure wherein a first electrode, an organic substance layer, and a second electrode are sequentially laminated on a substrate, a random nano structure having a fine pattern of a peaks-and-valleys shape is formed between a substrate and a first electrode to extract any light that is wasted due to total reflection and an optical waveguide mode to the outside of the substrate so that an organic light emitting device with improved external quantum efficiency can be realized, and optical extraction patterns and color changes due to visual field angles can also be improved.