Organic Light-Emitting Device Emission Zone Stability
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Solution Overview
Problem
In organic light-emitting devices with a double-stack structure, the emission zones can change over time due to imbalanced hole and electron mobility, leading to reduced lifespan and efficiency.
Innovation Solution
The organic light-emitting device is configured with emission layers in each stack having different properties, such as varying hole and electron transport rates, to maintain charge balance and prevent emission zone shifts, using distinct hosts with different hole and electron mobilities and HOMO energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If emission layers with identical properties are used in both stacks, then the device structure is simple and manufacturing is easier, but the emission zones change over time due to imbalanced hole and electron mobility
Solution Approach 1:
The patent applies local quality by configuring the emission layers in the two stacks with different properties. Specifically, the first emission layer has different host materials, dopants, or thickness compared to the second emission layer, creating localized differences that compensate for the imbalanced hole and electron mobility in different regions of the device. This ensures stable emission zones throughout the device operation.
2Duration of action of stationary object
If emission layers with different properties are used in each stack, then the emission zone stability is improved and lifespan is extended, but the manufacturing precision and material selection complexity increase
Solution Approach 1:
The patent implements parameter changes by systematically varying key parameters of the emission layers including host materials (e.g., TPBi vs. TCTA), dopant concentrations, and layer thicknesses. These parameter adjustments are designed to balance the charge transport characteristics in each stack, thereby stabilizing the emission zones and extending device lifespan while maintaining controllable manufacturing processes.
3Reliability
If the hole and electron mobility are imbalanced in the emission layers, then the device structure is simpler, but electrons or excitons accumulate at the interface reducing efficiency
Solution Approach 1:
The patent applies asymmetry by deliberately designing the emission layers in the two stacks with non-identical properties. The first stack's emission layer and the second stack's emission layer have asymmetric configurations in terms of host materials, dopant types, or thickness, which creates complementary charge transport characteristics that balance hole and electron mobility across the entire device structure.
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 the lifespan and efficiency of the organic light-emitting device by maintaining the emission zone and balancing charge supply, resulting in improved light emission characteristics and extended device life.
Implementation Method 1
electrons and holes from the two electrodes are injected into the organic emission layer, and excitons are produced in the organic emission layer via combination of the electrons and holes. Then, when the produced excitons fall from the excited state to the ground state, light is generated from the organic light-emitting device.
Data Source
AI summary
An organic light-emitting device and an organic light-emitting display device using the same are discussed. In a structure in which emission layers that emit light having the same color are provided in a plurality of stacks, the emission layers have different properties such that the light emission efficiencies of the stacks are made uniform, whereby the lifespan of the organic light-emitting device is increased through charge balance.