Zinc Oxide ETL Surface Modification for QLED Carrier Balance
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Solution Overview
Problem
The existing methods for improving carrier injection balance in QLED devices by inserting an electron barrier layer are difficult to implement practically due to strict thickness requirements and increase production costs, making it challenging to achieve high external quantum efficiency.
Innovation Solution
A QLED device structure utilizing a zinc oxide electron transport layer with a surface hydroxyl content greater than or equal to 0.6 or modified with amino ligands and carboxyl ligands, which reduces electron mobility and injection efficiency, achieving carrier balance without the need for additional barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electron barrier layer is inserted to reduce electron mobility and achieve carrier injection balance, then external quantum efficiency is improved, but device structure becomes more complex and production cost increases
Solution Approach 1:
The patent changes the surface properties of the zinc oxide ETL by controlling hydroxyl content (achieving surface hydroxyl content ≥0.6) or by modifying with ligands (amino ligands and/or carboxyl ligands with 8-18 carbon atoms). This parameter change in surface chemistry reduces electron mobility and achieves carrier injection balance without adding structural layers, thereby improving external quantum efficiency while avoiding increased device complexity
Solution Approach 2:
The patent applies local quality modification by treating only the surface of the zinc oxide ETL differently from its bulk. The surface is modified with high hydroxyl content or coated with specific ligands, creating a localized region with different electron mobility properties. This allows the ETL to have high electron mobility in the bulk for efficient transport while having reduced electron injection capability at the surface interface, achieving carrier balance without structural complexity
2Reliability
If an electron barrier layer is inserted to achieve carrier injection balance, then external quantum efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent modifies the surface parameters of the zinc oxide ETL through hydroxyl content control (≥0.6) or ligand modification during the existing ETL fabrication process. This eliminates the need for separate barrier layer deposition steps, reducing manufacturing complexity and cost while achieving the same carrier injection balance effect that would otherwise require additional layers
Solution Approach 2:
The patent makes the zinc oxide ETL perform multiple functions: it serves as both the electron transport layer (providing high electron mobility in bulk) and the electron barrier layer (providing reduced electron injection at surface) through its modified surface properties. This multi-functionality eliminates the need for separate barrier layer materials and deposition processes, reducing manufacturing cost while achieving carrier injection balance
3Reliability
If an electron barrier layer is inserted to achieve carrier injection balance, then external quantum efficiency is improved, but the manufacturing process becomes more difficult to implement
Solution Approach 1:
The patent achieves carrier injection balance by changing surface parameters (hydroxyl content ≥0.6 or ligand modification) of the zinc oxide ETL during the existing solution processing steps. This integrates the barrier function into the standard ETL fabrication process without requiring additional deposition equipment or complex multi-step processes, making it easy to implement in existing manufacturing lines
Solution Approach 2:
The patent merges the electron barrier function with the electron transport function by modifying the surface of the zinc oxide ETL in place. Instead of separating these functions into distinct layers requiring separate fabrication steps, the surface-modified ETL simultaneously provides both high bulk electron mobility and reduced surface electron injection, simplifying the manufacturing process while achieving carrier injection balance
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
This approach enhances the external quantum efficiency of QLED devices while simplifying the manufacturing process and reducing costs by regulating electron injection through surface modifications rather than altering the device structure.
Implementation Method 1
an electron mobility of the Zinc oxide material is up to 10−3 cm2/V·S
Implementation Method 2
a surface hydroxyl content greater than or equal to 0.6
Implementation Method 3
a surface of at least some of the zinc oxide contains amino ligands and/or carboxyl ligands with 8-18 carbon atoms
Data Source
AI summary
The present application discloses a QLED and a preparation method thereof. The QLED comprises an anode and a cathode being oppositely arranged, a quantum dot luminescent layer arranged between the anode and cathode, and an ETL arranged between the quantum dot luminescent layer and the cathode. Where the ETL includes a first ETL, and the first ETL is a zinc oxide film with a surface hydroxyl content being greater than or equal to 0.6. Or alternatively, the ETL contains zinc oxide, and the surface of at least some of the zinc oxide contains amino ligands and/or carboxyl ligands with 8-18 carbon atoms. The QLED provided in the present application improves an external quantum efficiency of the QLED device effectively.