Imide Derivative Hole Transport Layer for Low-Voltage Organic EL
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Solution Overview
Problem
Existing organic electroluminescent (EL) devices require high voltages for sufficient luminance, leading to shortened device lifetime and increased power consumption, and current leakage issues due to unstable electron-receiving compounds like tetrafluorodicyanoquinodimethane, which also contaminate the apparatus during fabrication.
Innovation Solution
A novel imide derivative with electron-withdrawing groups, derived from pyromellitic acid, is used as a hole transporting or injecting layer material in organic EL devices, offering improved electron-receiving properties, heat resistance, and reduced scattering during film formation, allowing for low-voltage operation and extended device lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high voltage is applied to obtain sufficient luminance, then luminance is improved, but device lifetime is shortened and power consumption increases
Solution Approach 1:
The patent changes the chemical parameters of the hole transporting material by introducing electron-receiving groups (imide structures with carbonyl and imine groups) to modify the electronic properties. This allows the material to efficiently transport holes at lower voltages, resolving the contradiction between luminance and device lifetime by enabling sufficient luminance output without high voltage stress that would otherwise degrade the device
2Illumination intensity
If high voltage is applied to obtain sufficient luminance, then luminance is improved, but power consumption increases
Solution Approach 1:
The patent modifies the electronic parameters of the hole transporting layer by incorporating imide derivatives with strong electron-receiving capabilities. This changes the charge transport efficiency, allowing sufficient luminance to be achieved at lower operating voltages and reduced current densities, thereby decreasing power consumption while maintaining required luminance levels
3Ease of operation
If electron-receiving compounds are used to improve hole injection, then hole injection efficiency is improved, but device stability deteriorates due to heat resistance issues
Solution Approach 1:
The patent changes the thermal and electronic parameters of the hole transporting material by selecting imide derivatives that possess both strong electron-receiving properties and high thermal stability. The rigid imide core structure with resonance-stabilized electron distribution provides heat resistance while maintaining efficient charge transport, thus improving hole injection without compromising device stability
4Ease of manufacture
If low molecular weight electron-receiving compounds are used, then ease of deposition is improved, but apparatus contamination increases due to sublimation
Solution Approach 1:
The patent changes the molecular weight and intermolecular interaction parameters of the electron-receiving compound by designing imide derivatives with larger molecular structures and stronger intermolecular forces. This increases the sublimation temperature and reduces vapor pressure, allowing the material to be deposited by vacuum evaporation without excessive sublimation that would contaminate the apparatus, while still maintaining good film-forming properties
5Ease of operation
If electron-receiving compounds are used to improve hole injection, then hole injection efficiency is improved, but device stability deteriorates due to handling instability
Solution Approach 1:
The patent changes the physical and chemical stability parameters of the electron-receiving compound by incorporating imide structures with rigid frameworks and strong intramolecular bonds. This provides thermal stability, oxidation resistance, and chemical inertness, making the material stable during handling, storage, and device fabrication while maintaining efficient hole injection performance
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 imide derivative enables organic EL devices to be driven at low voltages while maintaining long lifetimes and preventing contamination, thus enhancing the stability and efficiency of the devices.
Implementation Method 1
the imide derivatives have electron receiving properties and excel in heat resistance
Implementation Method 2
these compounds form charge transfer complexes with amine derivatives of donor compounds
Implementation Method 3
a fluorescent material emits light by the recombination energy of holes injected from an anode and electrons injected from a cathode when an electric field is applied
Implementation Method 4
fabricating an organic EL device by vacuum deposition
Data Source
AI summary
An imide derivative represented by the following formula (A):wherein Ra and Rb are each a hydrogen atom, a halogen atom, a cyano group, an alkyl group, a fluoroalkyl group or an aryl group; at least one of Ra and Rb is a fluoroalkyl group; and Rc and Rd are each a substituted or unsubstituted benzyl group, an aryl group, a heterocycle, a fluoroalkyl group or an imide group.