OLED Electron-Transport Layer with Graded Metal Concentration
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Solution Overview
Problem
Current display devices face challenges in achieving long lifetime, high reliability, large size, high productivity, and high display quality, particularly in light-emitting apparatuses like OLEDs and QLEDs, where maintaining low electron injection and achieving efficient light extraction are difficult.
Innovation Solution
A display device structure incorporating a microcavity structure with specific layer configurations, including a first and second light-emitting device with distinct organic compounds for blue and red/green colors, and an electron-transport layer with a varying concentration of a metal or organometallic substance, optimized for efficient hole injection and electron transport, and the use of shared layers to simplify the manufacturing process and enhance light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a conventional light-emitting device structure is used, then the device can be manufactured with standard processes, but the driving lifetime is limited and initial decay occurs
Solution Approach 1:
The electron-transport layer is designed with non-uniform composition: a first region containing both electron-transport material and metal/organometallic salt, and a second region containing only electron-transport material. This local variation in material composition optimizes electron injection at the interface while maintaining efficient transport in the bulk, thereby extending driving lifetime and reducing initial decay.
Solution Approach 2:
The invention changes the chemical composition parameters of the electron-transport layer by introducing metal or organometallic salts in the first region. This parameter modification enhances electron injection efficiency and stabilizes the operating voltage over time, directly addressing the lifetime and reliability issues.
2Reliability
If separate layers are used for different light-emitting devices, then each device can be optimized independently, but the manufacturing process becomes complex and productivity decreases
Solution Approach 1:
The invention merges the electron-transport layers of multiple light-emitting devices into a single shared layer. This common layer contains regions tailored for different devices (first region for blue device, second region for red/green device), enabling independent optimization of each device while simplifying the manufacturing process and improving productivity.
Solution Approach 2:
The shared electron-transport layer serves multiple functions: it acts as the electron-transport layer for both the blue light-emitting device and the red/green light-emitting device, while also providing structural support and electrical connection. This multi-functionality reduces the total number of layers and manufacturing steps.
3Illumination intensity
If high electron injection is achieved, then efficient light emission can be obtained, but the device lifetime is reduced due to excessive electron accumulation
Solution Approach 1:
The electron-transport layer is designed with non-uniform composition: a first region containing both electron-transport material and metal/organometallic salt, and a second region containing only electron-transport material. This local variation in material composition optimizes electron injection at the interface while maintaining efficient transport in the bulk, thereby extending driving lifetime and reducing initial decay.
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 proposed solution extends the driving lifetime of the display device, increases reliability, and enables high productivity while achieving high display quality by optimizing light emission efficiency and reducing initial decay, thus addressing the limitations of existing technologies.
Implementation Method 1
Light-emitting devices (also referred to as EL devices or EL elements) utilizing an electroluminescence (hereinafter referred to as EL) phenomenon
Implementation Method 2
The electron-transport layer contains a third organic compound and a first substance. The third organic compound is an electron-transport material.
Implementation Method 3
A display device structure incorporating a microcavity structure with specific layer configurations
Data Source
AI summary
A display device having a long lifetime is provided. The display device includes a first light-emitting device and a second light-emitting device. The first light-emitting device includes a first electrode and a common electrode. The second light-emitting device includes a second electrode and a common electrode. The first light-emitting device includes a first light-emitting layer and an electron-transport layer in this order from a side of one of the first electrode and the common electrode which functions as an anode. The second light-emitting device includes a second light-emitting layer between the second electrode and the common electrode. The first light-emitting layer contains a first organic compound emitting light of a first color. The second light-emitting layer contains a second organic compound emitting light of a second color. The electron-transport layer contains a third organic compound and a first substance. The third organic compound is an electron-transport material. The first substance is a metal, a metallic salt, a metal oxide, or an organometallic salt. The electron-transport layer includes a first region and a second region which differ in a concentration of the first substance.