OLED Hole Injection Layer Composition for Lower Operating Voltage
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Solution Overview
Problem
Existing organic electronic devices face challenges in achieving balanced hole and electron injection, leading to high operating voltages and reduced efficiency, particularly in the hole injection layer, which affects the performance of organic light-emitting diodes (OLEDs).
Innovation Solution
The introduction of a hole injection layer comprising an organic matrix compound and a metal complex with a specific HOMO level alignment, where the HOMO level difference between the emitter matrix compound and the organic matrix compound is within a defined range (-0.24 eV to 0.8 eV), optimized for vacuum thermal evaporation, to enhance hole injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional hole injection layer is used, then the device structure is simple, but the hole injection efficiency is insufficient leading to high operating voltage
Solution Approach 1:
The hole injection layer is constructed as a composite material combining an organic matrix compound and a metal complex. This composite structure enables synergistic effects where the metal complex enhances hole injection efficiency while the organic matrix provides structural stability, thereby reducing operating voltage without excessive complexity
Solution Approach 2:
The invention optimizes the HOMO energy level parameter by selecting specific combinations of organic matrix compounds and metal complexes. By tuning the HOMO levels to satisfy the relationship HOMO(EMC) - HOMO(OMC) ≤ 0.3 eV, the device achieves improved hole injection efficiency and reduced operating voltage
2Reliability
If the hole injection layer characteristics are not optimized, then the device structure is simple, but the charge balance between holes and electrons is poor leading to reduced efficiency and lifetime
Solution Approach 1:
The invention systematically optimizes key parameters including HOMO energy levels, doping concentrations, and layer thicknesses. By controlling the HOMO level difference between emitter and organic matrix compounds to be ≤ 0.3 eV, and adjusting metal complex doping at 1-50 wt%, the device achieves balanced charge injection and extended lifetime
Solution Approach 2:
The metal complex acts as an intermediary substance that facilitates balanced charge transport between the anode and emission layer. It mediates hole injection efficiency while working synergistically with the organic matrix compound to achieve overall charge balance, improving both efficiency and device lifetime
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 configuration results in improved operating voltage and efficiency of organic electronic devices, making them suitable for mass production while maintaining low power consumption and extended device lifetime.
Implementation Method 1
When a voltage is applied to the anode and the cathode, holes injected from the anode move to the EML, via the HIL and HTL
Implementation Method 2
wherein the HOMO level of the emitter matrix compound (EMC) and the HOMO level of the organic matrix compound (OMC) fulfills the following equation: HOMO(EMC) - HOMO(OMC) ≤ 0.3 eV
Implementation Method 3
suitable for mass production via vacuum thermal evaporation
Implementation Method 4
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted
Data Source
AI summary
The present invention relates to an organic electronic device comprising an anode layer, a cathode layer, at least one emission layer (EML) and at least one hole injection layer (HIL), wherein the hole injection layer is arranged between the anode layer and the at least one emission layer.