Transparent OLED Top Electrode Composition for Efficient Electron Injection
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Solution Overview
Problem
Existing OLED displays with transparent top electrodes, such as those made from thin-film magnesium-silver alloys, suffer from poor luminous efficiency and increased power consumption due to the low transmittance and mismatched work function of silver, which limits their performance.
Innovation Solution
A top electrode comprising a composite material of silver, magnesium, and lithium fluoride, co-deposited via evaporation, is used to form a film with a thickness of approximately 5 nm to 25 nm, optimizing the ratios of precious metals, alkaline earth metals, and alkali metal compounds to enhance luminous efficiency while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Ag-rich Mg-Ag alloy films are used to increase light extraction, then luminous efficiency is improved, but power consumption increases due to mismatched work function
Solution Approach 1:
The patent uses a composite material consisting of Mg-Ag alloy combined with LiF layer. The Mg-Ag alloy provides high light extraction efficiency, while the LiF layer with its low work function (2.9 eV) improves electron injection, thereby reducing power consumption. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent optimizes the thickness parameters of each layer: Mg-Ag alloy layer thickness of 3-7 nm and LiF layer thickness of 0.5-2 nm. By precisely controlling these parameter ranges, the electrode achieves optimal balance between light extraction efficiency and electron injection performance, resolving the power consumption issue.
2Illumination intensity
If thin-film Mg-Ag alloy is used for transparent electrode, then transparency is achieved, but luminous efficiency is poor due to low transmittance
Solution Approach 1:
The patent creates a composite transparent electrode combining Mg-Ag alloy with LiF. The Mg-Ag alloy provides necessary electrical conductivity and work function matching, while the LiF layer enhances transparency and light extraction. This composite approach overcomes the limitations of single-material electrodes.
Solution Approach 2:
The patent applies different materials with specific local functions: the Mg-Ag alloy layer (3-7 nm) provides electrical properties and work function matching, while the LiF layer (0.5-2 nm) provides transparency enhancement and electron injection improvement. Each layer is optimized for its specific local function to achieve overall high luminous efficiency.
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 solution achieves high luminous efficiency and low power consumption, improving the overall performance of OLED displays by enabling better light extraction and reducing voltage requirements.
Implementation Method 1
the materials are co-deposited via evaporation, such as thermal evaporation or e-beam evaporation
Implementation Method 2
the materials are co-deposited via evaporation, such as thermal evaporation or e-beam evaporation
Implementation Method 3
the materials are co-deposited via evaporation, such as thermal evaporation or e-beam evaporation
Data Source
AI summary
Aspects of the present disclosure describe systems, methods, and structures that provide organic light-emitting diodes having high luminous efficiency and low electrical dissipation. Embodiments in accordance with the present disclosure include a top electrode normally comprising a single film that includes a pair of metals and one metal compound, where the metals include a precious metal in combination with an alkaline earth metal or rare-earth metal and the metal compound is an alkali metal compound. As a result, such a top electrode has a work function that is better matched for efficient electron injection than magnesium-silver alloy-based transparent electrodes known in the prior art.