Light-Emitting Electrochemical Cell Ionic Compound Ester Bond
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Solution Overview
Problem
Existing organic electroluminescent (EL) devices require complex multi-layer structures and restrictive electrode material selection due to their light emission mechanism, limiting their efficiency and manufacturing cost-effectiveness compared to self-emitting devices like light-emitting electrochemical cells (LECs).
Innovation Solution
A light-emitting electrochemical cell with an emitting layer containing a phosphonium or ammonium ionic compound having an anion with an ester bond, which enhances compatibility with various light-emitting substances, facilitating uniform surface emission and increased brightness at low voltage without the need for a multi-layer structure or specific electrode material considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-layer structure with injection layers and transport layers is used in organic EL devices, then hole or electron injection efficiency and recombination efficiency are improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent combines the functions of the emitting layer, hole injection layer, electron injection layer, hole transport layer, and electron transport layer into a single integrated emitting layer containing an ionic compound. This merging eliminates the need for separate injection and transport layers, reducing device complexity while maintaining injection and recombination efficiency through the ionic compound's ability to facilitate charge carrier injection and transport simultaneously
Solution Approach 2:
The ionic compound in the emitting layer performs multiple functions simultaneously: it acts as a hole source, electron source, hole transport medium, electron transport medium, and light-emitting material host. This multi-functionality replaces the need for multiple specialized layers in conventional organic EL devices, simplifying the overall device structure while maintaining high injection and recombination efficiency
2Reliability
If restrictive electrode material selection based on work function is applied in organic EL devices, then injection efficiency is improved, but ease of manufacture and material selection flexibility decrease
Solution Approach 1:
The ionic compound in the emitting layer autonomously provides charge carriers (holes and electrons) and facilitates their injection into the electrodes without requiring precise matching of electrode work functions. The ionic compound self-adjusts to enable efficient injection, eliminating the need for careful electrode material selection based on work function considerations, thereby simplifying manufacturing and expanding material choice flexibility
3Ease of operation
If conventional ionic compounds are used in LECs, then ion rearrangement on electrode interfaces is facilitated, but compatibility with various light-emitting substances and film properties are limited
Solution Approach 1:
The patent employs a composite ionic compound system comprising a specific cation (such as imidazolium, pyridinium, or ammonium) paired with a particular anion (such as tetrafluoroborate, hexafluorophosphate, or BF4-). This composite structure combines the benefits of rapid ion rearrangement (from the cation's interface activity) with enhanced compatibility and improved film properties (from the anion's chemical characteristics), achieving versatility across different light-emitting substances while maintaining high ion rearrangement rates
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 use of the ionic compound with an ester bond in the emitting layer of LECs achieves high luminance and improved film properties, enabling efficient light emission with reduced power consumption and simplified manufacturing, overcoming the limitations of traditional organic EL devices.
Implementation Method 1
the cations and anions of the salt move in the emitting layer toward the negative and the positive electrode, respectively, to provide a large electric field gradient (electric double layer) on the electrode interface
Implementation Method 2
to provide a large electric field gradient (electric double layer) on the electrode interface
Implementation Method 3
a voltage is applied to the organic thin film between the positive and the negative electrode to inject holes and electrons; the holes and electrons are recombined in the organic thin film; and the excitons generated by the recombination return to the ground state thereupon to emit light
Data Source
AI summary
A light-emitting electrochemical cell 10 includes an emitting layer 12 and electrodes 13 and 14, one on each side of the emitting layer 12. The emitting layer 12 contains a light-emitting material and an ionic compound. The ionic compound has general formula (1), wherein M is N or P; R1, R2, R3, and R4 each independently represent a C1-C20 saturated aliphatic group; and X is preferably an anion having a phosphoric ester bond or a sulfuric ester bond. The light-emitting material is preferably an organic light-emitting polymer, a metal complex, an organic low molecular compound, or a quantum dot.