Metal Nanowire Transparent Electrodes for OLED Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional OLEDs suffer from low light out-coupling efficiency due to total internal reflection at the interface between the organic stack and the substrate, leading to a significant portion of generated light being waveguided rather than externally emitted.
Innovation Solution
Incorporating a nanostructure layer with metal nanostructures and an anti-reflective layer between the substrate and the organic stack, which reduces waveguide modes and enhances light out-coupling by modifying the refractive index profile and introducing scattering centers to extract trapped light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional OLED structure with transparent electrodes is used, then the device can emit light, but a substantial portion of the generated light is waveguided due to total internal reflection at the interface between the organic stack and substrate, resulting in low light out-coupling efficiency
Solution Approach 1:
An anti-reflective layer with intermediate refractive index (1.7-1.9) is introduced between the substrate (refractive index ~1.5) and the organic stack (refractive index ~1.7-1.8). This intermediary layer reduces the refractive index mismatch at the interface, minimizing total internal reflection and waveguide modes while maximizing light out-coupling efficiency.
Solution Approach 2:
The refractive index profile of the optical stack is modified by introducing the anti-reflective layer with a specific refractive index range (1.7-1.9). This parameter change optimizes the optical impedance matching between layers, reducing reflection losses and improving light extraction efficiency without requiring complex multi-layer structures.
2Loss of energy
If the refractive index mismatch between the organic stack and substrate is reduced to minimize total internal reflection, then light out-coupling efficiency improves, but the device structure becomes more complex
Solution Approach 1:
A single anti-reflective layer serves as an intermediary between the substrate and organic stack, providing optimal refractive index matching. This simple single-layer approach achieves effective light out-coupling enhancement without the complexity of multiple alternating high-index and low-index layers.
Solution Approach 2:
By carefully selecting the refractive index of the anti-reflective layer (1.7-1.9) and optimizing its thickness, the patent achieves maximum light extraction efficiency with a minimal structural modification. The parameter optimization allows a single layer to perform the function that would otherwise require complex multi-layer interference structures.
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
Significantly improves light out-coupling efficiency by reducing waveguided light energy density and maximizing external light emission, thereby enhancing the performance of OLEDs and photovoltaic cells.
Implementation Method 1
modifying the refractive index profile
Implementation Method 2
total internal reflection at the interface between the organic stack and the substrate
Implementation Method 3
introducing scattering centers to extract trapped light
Data Source
AI summary
The present disclosure relates to OLED and PV devices including transparent electrodes that are formed of conductive nanostructures and methods of improving light out-coupling in OLED and input-coupling in PV devices.