Light Extraction Substrate with Nanoparticles and Roughness
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) and photovoltaic cells suffer from low light extraction efficiency due to the optical waveguide effect, where a significant portion of emitted light is trapped within the device, and solar cells have low conversion efficiency due to limited light absorption near the semiconductor junction.
Innovation Solution
A light extraction substrate with a glass substrate incorporating oxide nanoparticles up to 50 µm depth from one surface and a textured or coated surface with a roughness of at least 10 nm on the other, reducing the waveguide effect and enhancing light scattering for increased light emission and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLED devices are used with smooth substrates, then the device structure is simple and manufacturing is easier, but light extraction efficiency is low due to the optical waveguide effect trapping 80% of emitted light
Solution Approach 1:
The patent incorporates oxide nanoparticles (such as silica, alumina, titania, zirconia, or zinc oxide) into the substrate to create a porous or particulate structure. This porous material approach scatters light effectively while maintaining manufacturing feasibility through established nanoparticle incorporation techniques during substrate fabrication
Solution Approach 2:
The patent creates light extraction regions at different depths within the substrate - a first light extraction region at a first depth and a second light extraction region at a second depth greater than the first depth. This multi-depth approach extracts light from multiple dimensional layers, significantly improving light extraction efficiency while maintaining manufacturing practicality
2Volume of moving object
If thin film PV cells are used, then the device is thinner and more compact, but light absorption efficiency is low with only 6-7% conversion efficiency due to limited absorption near the junction
Solution Approach 1:
The patent applies the same porous substrate structure with oxide nanoparticles to photovoltaic devices, creating light scattering regions that trap and extend the path of incident light near the semiconductor junction, thereby increasing absorption probability without increasing device thickness
Solution Approach 2:
The multi-depth light extraction/absorption regions are applied to PV cells, with regions at different depths within the substrate to maximize light absorption at various penetration depths, enhancing energy conversion efficiency while maintaining the thin-film compact structure
3Device complexity
If only a single light extraction region is used, then the device structure is simpler, but light extraction efficiency is insufficient to overcome the waveguide effect
Solution Approach 1:
The patent implements light extraction regions at multiple depth levels within the substrate - a first light extraction region at a first depth and a second light extraction region at a second depth greater than the first depth. This vertical dimensional stratification allows light to be extracted at multiple stages as it propagates through the substrate, significantly enhancing overall extraction efficiency
Solution Approach 2:
The substrate is segmented into multiple functional regions with different light extraction properties at different depths. The first light extraction region and second light extraction region are distinct segments that work together to progressively extract light, dividing the light extraction function across multiple structural segments
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 substrate design increases light extraction in OLEDs and absorption in solar cells, leading to improved efficiency and energy conversion rates by reducing light trapping and enhancing light scattering, thereby overcoming the limitations of conventional technologies.
Implementation Method 1
enhancing light scattering for increased light emission and absorption
Implementation Method 2
The second light extraction region has a surface roughness of at least 10 nm
Implementation Method 3
the optical waveguide effect in which the light emitted from the organic emitting layer is reflected back from the interface
Data Source
Figure 1
AI summary
A light extraction substrate includes a glass substrate having a first surface and a second surface. A first light extraction region can be defined on and/or adjacent the first surface. The first light extraction region includes nanoparticles. A second light extraction region can be defined on at least a part of the second surface. The second light extraction region has a surface roughness of at least 10 nm.