Top Emission OLED Charge Balance and Lifetime
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Solution Overview
Problem
Top emission organic light emitting devices face increased power consumption and reduced lifetime due to progressive driving voltage issues, particularly in blue devices, where oxygen plasma treatment can lead to metal oxide formation in the metal reflective layer, compromising performance.
Innovation Solution
A top emission organic light emitting device is enhanced by incorporating a metal reflective layer, a first intermediate layer with a charge-transfer complex, and a second intermediate layer comprising a fullerene-based material or fluorine-containing compound, which improves charge balance and prevents electron-induced deterioration of the hole transport layer, thereby enhancing driving voltage and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen plasma treatment is applied to the anode surface, then surface energy is improved for better buffer layer formation, but oxygen penetrates into the metal reflective layer causing metal oxide formation that reduces lifetime and increases progressive driving voltage
Solution Approach 1:
A buffer layer comprising a hole transport layer and an electron blocking layer is introduced as an intermediary between the anode and the emission layer. This buffer layer prevents oxygen from penetrating into the metal reflective layer while maintaining good interface properties, thus resolving the contradiction between improving buffer layer formation quality and preventing metal oxide formation that reduces device lifetime
Solution Approach 2:
The patent uses a sacrificial buffer layer structure that can be formed through conventional plasma treatment processes. The buffer layer acts as a protective barrier that absorbs the harmful effect of oxygen diffusion, sacrificing itself to protect the metal reflective layer from oxidation, thereby extending device lifetime without compromising manufacturing simplicity
2Reliability
If oxygen plasma treatment is applied to the anode surface, then surface energy is improved for better buffer layer formation, but metal oxide formation increases progressive driving voltage
Solution Approach 1:
The buffer layer comprising hole transport and electron blocking layers serves as a mediator that prevents direct contact between oxygen and the metal reflective layer. By blocking oxygen diffusion paths, the buffer layer prevents metal oxide formation that would increase progressive driving voltage, while still allowing effective buffer layer formation through plasma treatment
Solution Approach 2:
The buffer layer creates an inert environment between the oxygen-containing plasma-treated anode surface and the metal reflective layer. This protective barrier effectively isolates the metal reflective layer from oxygen, preventing oxidation reactions that would lead to increased progressive driving voltage
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 structure improves driving voltage and lifetime characteristics by maintaining interfacial stability and preventing electron diffusion, resulting in more reliable top emission organic light emitting devices.
Implementation Method 1
a first intermediate layer including a charge-transfer complex on the first electrode
Implementation Method 2
a second intermediate layer including a fullerene-based material or a fluorine-containing compound on the first intermediate layer
Data Source
AI summary
A top emission organic light emitting device including a metal reflective layer, a first electrode, a first intermediate layer including a charge-transfer complex, a second intermediate layer including a fullerene-based material or a fluorine-containing compound, an emission layer, and a second electrode.