OLED Hole Injection Layer Doping for Lower Voltage and Longer Life
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Solution Overview
Problem
In organic electroluminescence devices, the mismatch between the energy levels of p-type conductive materials and hole transporting materials leads to inefficient hole injection and increased complexity due to the need for additional layers, resulting in higher voltage requirements and reduced device lifetime.
Innovation Solution
An organic electroluminescence device structure is developed using a deep-HOMO energy level hole transporting material doped with a deep-LUMO energy level p-type conductive material, eliminating the need for additional layers and enhancing the matching of energy levels for improved hole injection and transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type conductive material with LUMO energy level of −5.1 eV is used to dope the hole injection layer, then hole injection and conductivity are improved, but it cannot effectively match hole transporting materials with HOMO energy level of −5.2 eV or deeper
Solution Approach 1:
The patent changes the energy level parameter of the p-type conductive material from the conventional −5.1 eV to a deeper level (−5.2 eV or lower), enabling effective matching with hole transporting materials that have HOMO energy levels of −5.2 eV or deeper. This parameter change expands the adaptability while maintaining hole injection efficiency.
2Reliability
If an electron blocking layer is inserted between the hole transporting layer and the light-emitting layer to create progressive potential energy change, then hole transport is facilitated, but the total barrier height remains large and interface defects increase
Solution Approach 1:
The patent extracts and eliminates the electron blocking layer from the device structure. By using a hole transporting material with sufficiently deep HOMO energy level (−5.2 eV or deeper) in the hole injection layer, the patent achieves effective hole transport without requiring the additional electron blocking layer, thereby reducing device complexity and interface defects.
Solution Approach 2:
The patent merges the functions of the hole injection layer and the electron blocking layer by incorporating deep HOMO energy level hole transporting material directly into the hole injection layer. This combination eliminates the need for a separate electron blocking layer while maintaining effective hole injection and transport.
3Reliability
If multiple hole transporting materials are used to create progressive potential energy structure, then hole injection is improved, but the total barrier height from the first hole transporting layer to the light-emitting layer remains large
Solution Approach 1:
The patent changes the HOMO energy level parameter of the hole transporting material in the hole injection layer to −5.2 eV or deeper, which directly reduces the potential barrier height for hole injection into the light-emitting layer. This single parameter change eliminates the need for progressive potential energy structures and reduces the overall voltage requirement.
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 reduces the voltage required and increases the device's lifetime by simplifying the structure and reducing interface defects, while maintaining effective hole injection and transport.
Implementation Method 1
The p-type doping effect can be achieved through the strong electron-capturing ability of the p-type conductive doped material, which improves hole injection and conductivity.
Implementation Method 2
Organic electroluminescence devices (OLED) convert electrical energy into light by applying voltages across the device.
Implementation Method 3
The holes and electrons meet each other to form excitons, and the excitons recombine and emit light.
Data Source
AI summary
Disclosed is an organic electroluminescence device. The organic electroluminescence device has an organic layer having a specific combination in which a hole transporting material is doped with a p-type conductive doped material. The organic electroluminescence device can provide better device performance, such as lifetime improvement and voltage reduction.