Reflective Pixel Define Layer for OLED Light Extraction
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Solution Overview
Problem
Flexible display screens based on light-emitting diodes suffer from low light utilization, with only 20-40% of emitted light being used for display, and blue light emitting materials have limited brightness and short lifespan due to high driving voltage, leading to yellow tint as screens age.
Innovation Solution
The apparatus includes a pixel define layer with a hole containing a light emitting layer and reflective layers on the sidewall and bottom to enhance light reflection, with the reflective layers also providing electrical power, improving light utilization and extending lifespan without increasing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If driving voltage is increased to enhance blue light brightness, then brightness is improved, but lifespan is shortened and yellow tint occurs
Solution Approach 1:
The patent converts the harmful effect of high driving voltage (which shortens lifespan and causes yellowing) into a beneficial outcome by using reflective layers to improve light extraction efficiency. The reflective layers on the sidewall and bottom of the hole reflect light that would otherwise be lost, thereby enhancing blue light brightness without needing to increase driving voltage, thus preserving material lifespan and preventing yellow tint.
2Loss of energy
If light emitting layer is placed in a hole structure, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by making the reflective layers also serve as electrical power supply components. The reflective layers are configured to both reflect light from the light emitting layer and provide electrical power to it, thereby reducing the need for separate electrical connection structures and simplifying the overall device architecture while maintaining improved light extraction efficiency.
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 configuration increases light utilization for display and improves brightness while prolonging the lifespan of the display by reducing water vapor transmission and minimizing the impact of high driving voltage on blue light emitting materials.
Implementation Method 1
a first reflective layer on a sidewall of the hole and configured to reflect light emitted by the EML
Implementation Method 2
a second reflective layer on a bottom of the hole and configured to reflect the light emitted by the EML
Data Source
AI summary
Disclosed herein is an apparatus comprising: a pixel define layer (PDL) on a support and having a hole therein; a light emitting layer (EML) at least partially within the hole; and a first reflective layer on a sidewall of the hole and configured to reflect light emitted by the EML. Also disclosed herein is a display panel and a system comprising a plurality of the apparatus. Further disclosed herein is a method of making the apparatus.