OLED Light Scattering Layer for Trapped Light Extraction
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Solution Overview
Problem
Organic light-emitting diode (OLED) devices suffer from significant light loss due to internal reflection and absorption, resulting in inefficient light output and reduced sharpness in pixellated applications, as most of the generated light is trapped within the device rather than being emitted effectively.
Innovation Solution
Incorporating a light scattering layer between the substrate and encapsulating cover, along with a transparent low-index element, to redirect trapped light and reduce interlayer reflections, thereby enhancing light extraction and maintaining image sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a typical OLED device structure with glass substrate, transparent conducting anode, organic layers, and reflective cathode is used, then the device can generate light through electron-hole recombination, but nearly 60% of generated light is trapped by internal reflection in the ITO/organic EL element and 20% is trapped in the glass substrate, resulting in only about 20% light emission
Solution Approach 1:
The patent introduces a scattering layer as an intermediary component between the organic light-emitting layer and the encapsulating cover. This scattering layer mediates the interaction between trapped light and the device structure by redirecting light paths through scattering effects, enabling previously trapped light to escape and contribute to the light output, thereby resolving the contradiction between light generation and light extraction efficiency
Solution Approach 2:
The patent modifies the optical parameters of the device structure by introducing materials with different refractive indices and scattering properties. The scattering layer changes the light propagation parameters through scattering effects, altering the critical angle and light paths to reduce total internal reflection and improve light extraction efficiency, thus increasing light output while reducing energy loss
2Illumination intensity
If light scattering layer is introduced to extract trapped light, then light output is improved, but device structure complexity increases
Solution Approach 1:
The patent segments the optical path into distinct functional zones by introducing a scattering layer as a separate component. This segmentation allows independent optimization of light generation (organic layers) and light extraction (scattering layer) functions, improving light output while keeping the added structural complexity localized and manageable rather than throughout the entire device
3Manufacturing precision
If conventional OLED structure is used, then manufacturing is relatively simple, but sharpness in pixellated applications is reduced due to light trapping and lateral propagation
Solution Approach 1:
The scattering layer acts as an intermediary that redirects light paths to reduce lateral propagation of trapped light. By scattering light in controlled directions, it prevents light from traveling laterally across pixel boundaries, thereby improving image sharpness and manufacturing precision while maintaining relative manufacturing simplicity through the addition of a single functional layer
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 significantly increases light output and improves the sharpness of OLED devices by effectively redirecting trapped light and minimizing absorption losses, leading to more efficient light emission and maintaining image clarity.
Implementation Method 1
a light scattering layer located between the substrate and cover
Implementation Method 2
a transparent low-index element having a third refractive index lower than each of the first refractive index range and second refractive index
Data Source
AI summary
An organic light-emitting diode (OLED) device, comprising: a substrate; an OLED comprising first and second electrodes and one or more layers of organic light-emitting material formed between the electrodes, wherein at least one electrode comprises a transparent electrode, the transparent electrode and layer(s) of organic light-emitting material having a first refractive index range; and an encapsulating cover; wherein at least one of the substrate or cover comprises a transparent substrate or cover having a second refractive index and through which light from the OLED is emitted; and further comprising a light scattering layer located between the substrate and cover, and a transparent low-index element having a third refractive index lower than each of the first refractive index range and second refractive index and located between the scattering layer and the transparent substrate or cover.