OLED Dual Emissive Layer Host Energy Level Engineering
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Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges in achieving low power consumption and improved luminous efficiency and lifespan, particularly due to the limitations of fluorescent materials using only singlet excitons and phosphorescent materials with short commercial lifespans.
Innovation Solution
The OLED design incorporates a dual red emitting material layer structure with different N-type hosts having varying energy levels and electron mobility, minimizing exciton loss and promoting exciplex formation within the emissive layer to reduce driving voltage and enhance luminous efficiency and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent material is used to improve luminous efficiency, then luminous efficiency is improved, but luminous lifespan becomes short
Solution Approach 1:
The emissive layer is segmented into multiple layers with different functions: the first red emitting material layer uses phosphorescent material for high luminous efficiency, while the second red emitting material layer uses fluorescent material with longer lifespan. This segmentation allows each layer to contribute different properties to the overall device performance, resolving the contradiction between luminous efficiency and lifespan.
Solution Approach 2:
The patent employs a composite structure combining phosphorescent and fluorescent emitting materials in separate layers within the same emissive layer. The phosphorescent material (e.g., Ir(III) complexes) provides high luminous efficiency by utilizing both singlet and triplet excitons, while the fluorescent material provides extended lifespan. This composite approach integrates the advantages of both material types to resolve the technical contradiction.
2Duration of action of stationary object
If fluorescent material is used to extend luminous lifespan, then luminous lifespan is improved, but luminous efficiency becomes low
Solution Approach 1:
The emissive layer is divided into two distinct layers: the first layer utilizes phosphorescent material optimized for high luminous efficiency, while the second layer uses fluorescent material optimized for longer operational lifespan. This functional segmentation ensures that neither material type compromises the other's advantages, allowing the device to achieve both high efficiency and extended lifespan simultaneously.
3Use of energy by moving object
If dual red emitting material layers with different N-type hosts are used, then luminous efficiency and lifespan are improved, but device complexity increases
Solution Approach 1:
The emissive layer is segmented into two sub-layers, each with specific N-type hosts optimized for their respective emitting materials. This segmentation enables precise control over exciton management and electron-hole recombination processes, improving luminous efficiency and lifespan while maintaining a relatively simple overall device architecture that can be manufactured using conventional OLED processes.
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 approach results in an OLED with lower driving voltage, reduced power consumption, and improved luminous efficiency and lifespan by optimizing the energy levels and electron mobility of the N-type hosts in the emissive layer.
Implementation Method 1
the second N-type host has a lowest unoccupied molecular orbital (LUMO) energy level lower than a LUMO energy level of the first N-type host... The second N-type host can have electron mobility larger than an electron mobility of the first N-type host
Implementation Method 2
an emissive layer disposed between the first and second electrode, and including an emitting material layer... a first red emitting material layer including a first N-type host... a second red emitting material layer disposed between the first red emitting material layer and the second electrode
Data Source
AI summary
The present disclosure relates to an organic light emitting diode (OLED) where adjacent emitting material layers includes hosts with different LUMO energy level and/or electron mobility. A first emitting material layer including a first host with relatively slow electron mobility and/or relatively high LUMO energy level is disposed adjacently to a hole transport layer and a second emitting material layer including a second host with relatively fast electron mobility and/or relatively low LUMO energy level is disposed adjacent to an electron transport layer. No exciplex between hole transporting material and the first host is not formed while exciplex between the hole transporting material and the second host is formed so that exciton loss can be minimized. An OLED and an organic light emitting device with low driving voltage and low power consumption and beneficial luminous property and luminous lifetime can be realized.