Copolymer Hole Transport Layer for Quantum Dot Electroluminescence
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Solution Overview
Problem
Current quantum dot electroluminescence devices face challenges with luminous efficiency due to a large band offset between the hole transport layer and the light emitting layer, leading to increased driving voltage and reduced carrier injection efficiency.
Innovation Solution
A copolymer with a specific structural unit, represented by Chemical Formula 1, is introduced, which has a deep HOMO level, reducing the band offset and enhancing hole injection capability, thereby improving luminous efficiency and reducing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional hole transport material is used in quantum dot electroluminescence devices, then the device structure is simple, but the luminous efficiency is insufficient due to large band offset
Solution Approach 1:
The patent applies parameter changes by modifying the HOMO level of the hole transport material through specific molecular structure design. The copolymer in Claim 1 has a deep HOMO level (greater than -5.6 eV and less than or equal to -5.3 eV) which is achieved by adjusting chemical parameters (aromatic hydrocarbon groups, heterocyclic groups, substituent patterns). This parameter change reduces the band offset with the quantum dot light emitting layer, thereby improving hole injection efficiency and luminous efficiency without complicating the device structure.
Solution Approach 2:
The patent uses composite materials by combining different functional units in the copolymer structure. The copolymer includes aromatic hydrocarbon groups (Ar1, Ar2), aromatic heterocyclic groups, and substituent groups (R1, L1, Y) that work together to achieve the desired HOMO level and film-forming properties. This composite approach allows optimization of both luminous efficiency and material processability.
2Reliability
If the HOMO level of the hole transport layer is increased to reduce band offset, then carrier injection efficiency improves, but the material selection becomes more restricted
Solution Approach 1:
The patent systematically explores parameter changes in the molecular structure to achieve the target HOMO level range (> -5.6 eV and ≤ -5.3 eV). By adjusting the types of aromatic hydrocarbon groups (Ar1, Ar2), heterocyclic groups, substituent patterns (R1, L1, Y), and their combinations, the invention creates a family of materials that all satisfy the HOMO level requirement while offering different film-forming characteristics and processing properties, thus maintaining material selection flexibility.
3Loss of energy
If a deep HOMO level material is used to improve hole injection, then luminous efficiency increases, but film-forming properties may deteriorate
Solution Approach 1:
The copolymer structure combines electron-withdrawing groups (to achieve deep HOMO level for improved hole injection) with sterically hindering groups (to maintain good film-forming properties). The aromatic hydrocarbon groups and heterocyclic groups provide both the electronic properties needed for deep HOMO level and the steric bulk needed for proper film morphology and formation, resolving the contradiction between luminous efficiency and ease of manufacture.
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 copolymer achieves high luminous efficiency, long light emission life-span, and low driving voltage in quantum dot electroluminescence devices by improving hole injection and carrier transport, while maintaining excellent film-forming properties and solvent solubility.
Implementation Method 1
A copolymer with a specific structural unit, represented by Chemical Formula 1, is introduced, which has a deep HOMO level to reduce the band offset, improving hole injection capability
Implementation Method 2
Because quantum dots are very small in size, a surface area per unit volume is large. For this reason, the majority of atoms are present on the surface of the nanocrystals, and exhibit quantum confinement effects. Due to the quantum confinement effect, a quantum dot is able to adjust the emission wavelength by adjusting its size
Implementation Method 3
An EL device is a light emitting device including a thin film of several nanometers to several hundred nanometers between an anode and a cathode
Data Source
AI summary
A copolymer having a structural unit represented by Chemical Formula 1 is provided. The copolymer may improve performance, e.g., luminous efficiency, of an electroluminescence device.In Chemical Formula 1, the definition of each substituent is as described in the detailed description.