Copolymer Hole Transport Material for QD EL Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional quantum dot electroluminescent devices suffer from insufficient durability, particularly in terms of luminescence lifespan, due to significant band offset differences between the hole injection layer, hole transport layer, and light emitting layer, which affects carrier injection efficiency and luminous efficiency.
Innovation Solution
A copolymer with alternating structural units having shallow and deep HOMO levels is used in the hole transport layer, reducing band offset differences and improving hole injection ability, thereby enhancing the durability and reducing driving voltage of the electroluminescent device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hole transport materials are used in quantum dot electroluminescent devices, then device structure is simple, but durability and luminescence lifespan are insufficient due to significant band offset differences
Solution Approach 1:
The hole transport layer is segmented into multiple sub-layers with different HOMO levels. The copolymer introduces distinct structural units (first structural unit with deeper HOMO level, second structural unit with shallower HOMO level) that create staged band offsets, reducing the overall band offset difference between the hole transport layer and light emitting layer while maintaining layer integrity
Solution Approach 2:
The patent uses a copolymer composite material containing two different structural units within the same polymer chain. This composite structure combines the benefits of deep HOMO level (for efficient hole injection) and shallow HOMO level (for reduced band offset) in a single material, improving durability without increasing device complexity
2Ease of operation
If materials with deep HOMO level are used to improve hole injection ability, then hole injection efficiency improves, but band offset difference with light emitting layer increases, reducing luminous efficiency
Solution Approach 1:
The hole transport layer is divided into regions with different HOMO levels through the copolymer structure. The first structural unit provides deep HOMO level for efficient hole injection at the interface with hole injection layer, while the second structural unit provides shallow HOMO level at the interface with light emitting layer, minimizing energy loss
Solution Approach 2:
Different segments of the copolymer chain provide different local electronic properties. The first structural units are positioned to interact with the hole injection layer where deep HOMO is beneficial, while second structural units are positioned near the light emitting layer where shallow HOMO reduces band offset, optimizing both interfaces locally
Data Source
AI summary
Disclosed is a copolymer including a structural unit represented by Chemical Formula 1 capable of improving performance (particularly durability) of an electroluminescent device.