QLED Hole Injection Layer Nanoparticle Design
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Solution Overview
Problem
Existing quantum dot light-emitting diodes (QLEDs) suffer from low external quantum efficiency (EQE) and reliability due to issues such as organic ligand deterioration, poor carrier balance, and electron overflow.
Innovation Solution
A light-emitting element configuration that includes a first and second electrode, a light-emitting layer with a phosphor, and at least one function layer with high polarity and low vapor pressure solvents, optionally containing metal compound nanoparticles like nickel oxide, to enhance hole injection and improve carrier balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic ligands are used in the hole injection layer, then hole injection function is provided, but the organic ligands deteriorate due to electrochemical reaction and separate from quantum dots
Solution Approach 1:
The patent removes organic ligands from the hole injection layer composition and replaces them with inorganic hole transport materials. This extraction of the problematic organic component eliminates the electrochemical reaction that causes deterioration and separation, while maintaining the hole injection function through inorganic alternatives.
Solution Approach 2:
The patent employs inorganic hole transport materials that are more stable and longer-lasting compared to organic ligands. These inorganic materials do not deteriorate through electrochemical reactions, providing a durable solution that maintains functionality over the device lifetime without the need for replacement or degradation.
2Illumination intensity
If electrons are excessive in the light-emitting layer, then light emission is achieved, but electrons overflow to hole transport layer and hole injection layer reducing EQE
Solution Approach 1:
The patent modifies the energy level parameters of the hole injection layer by using inorganic materials with appropriate work functions and electron affinities. This parameter adjustment creates a more favorable energy landscape that prevents electron overflow from the light-emitting layer to the hole transport layer, thereby maintaining high external quantum efficiency while enabling effective light emission.
3Reliability
If inorganic hole transport material is used, then electrochemical stability is improved, but hole injection function must be maintained
Solution Approach 1:
The patent carefully selects inorganic hole transport materials with specific parameters including work function, electron affinity, and mobility to ensure they maintain hole injection functionality while providing electrochemical stability. The parameter optimization allows the inorganic material to fulfill both stability and functional requirements simultaneously.
Data Source
AI summary
A light-emitting layer includes quantum dots, a hole injection layer provided between an anode and the light-emitting layer with one face in contact with the anode includes nanoparticles, and an average particle diameter of the nanoparticles included in the hole injection layer is less than an average particle diameter of the quantum dots included in the light-emitting layer.