OLED Electron Injection Layers for Color Lifespan Balance
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Solution Overview
Problem
Existing organic electroluminescence display devices face challenges in balancing electron injection and emission lifespan across different light emitters, leading to uneven color lifespan and efficiency.
Innovation Solution
The device incorporates a first electron injection enhancing layer and an electron injection suppressing layer with specific ratios of Liq and electron transport materials, along with a second electron injection enhancing layer, to balance electron injection and emission across light emitters, improving color lifespan and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform electron injection layers are used across all light emitters, then device structure is simple, but electron injection is unbalanced leading to uneven color lifespan
Solution Approach 1:
The patent applies local quality by differentiating the electron injection enhancing layer into two types: a first electron injection enhancing layer with higher electron mobility for the first light emitter, and a second electron injection enhancing layer with lower electron mobility for the second light emitter. This localized differentiation balances the electron injection across different light emitters, ensuring uniform color lifespan while maintaining reasonable structural complexity.
2Productivity
If electron injection is increased for all light emitters, then emission efficiency improves, but emission lifespan becomes unbalanced
Solution Approach 1:
The patent implements local quality by assigning different electron mobility characteristics to different electron injection enhancing layers. The first electron injection enhancing layer has higher electron mobility to provide sufficient electrons to the first light emitter, while the second electron injection enhancing layer has lower electron mobility to prevent excessive electron injection to the second light emitter. This localized optimization achieves both high emission efficiency and balanced emission lifespan across different light emitters.
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 enhances the emission lifespan and efficiency of the organic electroluminescence display device by balancing electron injection, resulting in improved color visibility and operational longevity.
Implementation Method 1
Each of the first electron injection enhancing layer and the electron injection suppressing layer may include Liq, LiF, Li2O, CsF, BaF, BaO, Al2O3, NaCl, RbCl, or RbI, and an electron transport material
Implementation Method 2
The OLED may realize colors by using a principle in which holes and electrons, which are respectively injected into first and second electrodes, are recombined with each other to emit light. That is, when excitons in which the injected holes and electrons are combined with each other return from an excited state to a ground state, light may be emitted
Data Source
AI summary
An organic electroluminescence display device includes a first electrode, a first light emitter on the first electrode, the first light emitter including a first light emitting layer, a first charge generation layer disposed on the first light emitter, a second light emitter on the first charge generation layer, the second light emitter including a second light emitting layer, and a second electrode on the second light emitter. The first light emitter includes a first electron injection enhancing layer on the first light emitting layer. The second light emitter includes an electron injection suppressing layer on the second light emitting layer, the electron injection suppressing layer having electron mobility less than that of the first electron injection enhancing layer.