Patterned Light-Scattering Layer for OLED Light Extraction
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Solution Overview
Problem
Organic electroluminescent devices suffer from insufficient light emission due to total reflection at interfaces between high refractive index materials, which limits the transmission of light out of the device.
Innovation Solution
A light emitting device is designed with a patterned light-scattering layer on a substrate, featuring acute angles and a combination of low and high refractive index materials, where the electroluminescent device is disposed on the sidewalls of the patterned layer to scatter light and reduce reflection, increasing the amount of light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high refractive index materials are used for the organic electroluminescent layer and transparent conductive layer, then the light emission efficiency is improved, but total reflection occurs at the interfaces with substrate or air, reducing the light transmission
Solution Approach 1:
A light-scattering layer is introduced as an intermediary component between the high refractive index electroluminescent layer and the substrate/air interface. This layer has a lower refractive index than the electroluminescent layer, creating a gradual refractive index transition that reduces total internal reflection. The light-scattering layer contains scattering centers that redirect light at multiple angles, allowing more light to escape through the substrate interface rather than being totally reflected back into the device.
2Ease of manufacture
If the organic electroluminescent device uses conventional flat structure, then the manufacturing process is simple, but the light emission amount is insufficient due to total reflection
Solution Approach 1:
The light-scattering layer is designed with a porous or composite structure containing scattering centers distributed within the matrix material. This porous structure increases the path length of light through the layer and provides multiple scattering events, enhancing light extraction efficiency. The porous structure can be formed by incorporating particles, creating cavities, or using inherently porous materials that maintain ease of fabrication while significantly improving light emission.
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 patterned light-scattering layer effectively scatters light emitted from the electroluminescent device, allowing it to enter the substrate at different angles and increase the light emission amount, thereby enhancing the overall light output of the device.
Implementation Method 1
The patterned light-scattering layer effectively scatters light emitted from the electroluminescent device, allowing it to enter the substrate at different angles
Implementation Method 2
An organic electroluminescent device is a semiconductor device capable of efficiently converting electrical energy into optical energy
Implementation Method 3
The organic electroluminescent layer and a transparent conductive layer that acts as an electrode are both made of a material having a high refractive index. When the electrons and the holes are re-combined to produce light, parts of the light are refracted to generate incident light having a wide angle
Implementation Method 4
total reflection occurs at an interface between the transparent conductive layer and a substrate or at an interface between the substrate and the air
Data Source
AI summary
A light emitting device includes a substrate, a patterned light-scattering layer, and an electroluminescent device. The patterned light-scattering layer is disposed on a portion of the substrate. The patterned light-scattering layer has a bottom surface in contact with the substrate, a top surface opposite to the bottom surface, and a plurality of sidewalls connecting the bottom surface and the top surface. The electroluminescent device is at least disposed on the sidewalls.