Organic Intermediate Connector for Tandem OLED Drive Voltage
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Solution Overview
Problem
Conventional tandem OLEDs face challenges in achieving high luminous efficiency and long operational lifetime due to high drive voltage and manufacturing complexities associated with inorganic intermediate connectors, which also cause pixel crosstalk and low optical transparency.
Innovation Solution
A tandem OLED structure using n-doped organic layers and electron-accepting layers with organic materials having a reduction potential greater than −0.5 V vs. Saturated Calomel Electrode, constituting more than 50% of the electron-accepting layer, facilitates effective carrier injection and optical transparency, reducing drive voltage and manufacturing complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic materials are used to form intermediate connectors in tandem OLEDs, then electrical connection between EL units is achieved, but fabrication complexity increases and manufacturing becomes difficult
Solution Approach 1:
The patent replaces inorganic intermediate connectors with an organic intermediate connector comprising a hole-transporting layer and an electron-transporting layer. This substitution eliminates the need for complex inorganic material deposition processes while maintaining effective electrical connection between EL units through organic charge transport mechanisms
Solution Approach 2:
The intermediate connector is constructed as a composite structure with a hole-transporting layer and an electron-transporting layer, each performing specific functions. This composite organic structure achieves both hole injection into the lower EL unit and electron injection into the upper EL unit, simplifying manufacturing while ensuring reliable electrical connection
2Reliability
If inorganic intermediate connectors are used in tandem OLEDs, then electrical connectivity is provided, but optical transparency decreases and pixel crosstalk occurs
Solution Approach 1:
The patent substitutes inorganic connector materials with organic materials that possess inherent optical transparency and lack the pixel crosstalk issues associated with inorganic materials. The organic intermediate connector allows light to pass through while maintaining electrical connectivity through charge transport
Solution Approach 2:
The intermediate connector is designed with specific local properties: the hole-transporting layer and electron-transporting layer are positioned to facilitate charge injection in specific directions while maintaining optical transparency in the light emission path, thereby eliminating pixel crosstalk
3Illumination intensity
If high current density is applied to achieve high brightness in OLEDs, then luminance increases, but operational lifetime decreases
Solution Approach 1:
The patent divides a single high-current-density OLED into multiple EL units connected in series through an organic intermediate connector. Each EL unit operates at a lower current density, reducing degradation and extending lifetime, while the segmented structure maintains high overall luminance through additive light output from multiple units
Solution Approach 2:
The patent transitions from a single-plane OLED structure to a multi-layer stacked configuration with intermediate connectors between EL units. This dimensional change allows current to be distributed across multiple series-connected units, enabling high luminance through cumulative emission while keeping current density in each unit low enough to ensure long operational lifetime
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 solution enhances luminous efficiency and operational stability of tandem OLEDs by reducing drive voltage and maintaining high luminance over extended operational times while simplifying the manufacturing process.
Implementation Method 1
an intermediate connector disposed between adjacent electroluminescent units, wherein the intermediate connector includes an n-doped organic layer and an electron-accepting layer
Implementation Method 2
the electron-accepting layer includes one or more organic materials, each having a reduction potential greater than −0.5 V vs. a Saturated Calomel Electrode
Implementation Method 3
Holes and electrons recombine and emit light in the ETL near the interface of HTL/ETL
Data Source
AI summary
A tandem OLED includes an anode and a cathode. The OLED also includes at least two electroluminescent units disposed between the anode and the cathode, wherein each of the electroluminescent units includes at least one hole-transporting layer and one organic light-emitting layer. An intermediate connector is disposed between adjacent electroluminescent units, wherein the intermediate connector includes an n-doped organic layer and an electron-accepting layer, the electron-accepting layer being disposed closer to the cathode than the n-doped organic layer, and wherein the electron-accepting layer includes one or more organic materials, each having a reduction potential greater than −0.5 V vs. a Saturated Calomel Electrode, and wherein the one or more organic materials constitute more than 50% by volume of the electron-accepting layer.