OLED Hole Transporting Layer Electron Blocking via Segmented Organic Structure
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Solution Overview
Problem
In organic electroluminescence elements, the hole transporting layer fails to sufficiently block electrons, leading to deterioration and reduced lifetime, especially at high current densities, due to the band bending effect, and the limited types of materials available for the hole transporting layer hinder effective electron blocking.
Innovation Solution
A light emitting element with a functional organic layer containing a hole injecting layer and a hole transporting layer, both infused with electron transporting materials, where the content and thickness of these materials differ to enhance electron blocking and hole transport, using acene-based and amine-based materials for improved electron and hole transport properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hole transporting layer is used to block electrons, then electron blocking effect is improved, but the layer deteriorates due to electron damage at high current densities
Solution Approach 1:
The hole transporting layer is divided into two separate layers: a first hole transporting layer closer to the anode and a second hole transporting layer closer to the light emitting layer. This segmentation allows each layer to have optimized properties - the first layer can focus on hole transport while the second layer provides electron blocking capability, preventing electron damage to the hole transporting function.
Solution Approach 2:
An electron transporting layer is introduced as an intermediary between the light emitting layer and the hole transporting layers. This intermediary layer accepts electrons from the light emitting layer and transports them toward the anode, preventing electrons from accumulating in and damaging the hole transporting layer, thus extending its operational lifetime.
2Reliability
If materials with large energy gap are used for hole transporting layer to increase electron blocking, then electron blocking effect is improved, but material selection becomes limited
Solution Approach 1:
Instead of relying solely on materials with large energy gaps, the invention changes the structural parameters by introducing multiple hole transporting layers with different positions and functions, and by adding an electron transporting layer. This allows use of conventional hole transporting materials while achieving superior electron blocking through structural design rather than material property constraints.
Solution Approach 2:
The device uses a composite structure combining hole transporting materials and electron transporting materials in specific layers. The hole transporting layers use materials optimized for hole transport, while the electron transporting layer uses materials with electron transporting capability, creating a synergistic composite structure that achieves both functions without limiting material selection.
3Power
If drive voltage is increased to improve light emitting intensity, then current density increases, but electron blocking capability decreases due to band bending
Solution Approach 1:
By segmenting the hole transporting function into two layers positioned at different distances from the light emitting layer, the invention creates a gradient structure that manages electron transport more effectively. The second layer near the light emitting layer provides initial electron blocking, while the first layer provides additional protection, maintaining blocking capability even at high drive voltages.
Solution Approach 2:
The electron transporting layer acts as a mediator that facilitates electron movement away from the light emitting layer in a controlled manner. This prevents electron accumulation and band bending in the hole transporting layers, maintaining their electron blocking capability even when high drive voltages are applied to increase light emitting intensity.
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 efficiently transports holes, blocks electrons, and extends the lifetime of the light emitting element, balancing light emission properties and lifetime characteristics while maintaining low drive voltage, even at high current densities.
Implementation Method 1
a hole injecting layer which is provided in contact with the anode and contains a hole injecting material and a hole transporting layer which is provided in contact with the hole injecting layer and the light emitting layer and contains a hole transporting material
Implementation Method 2
the hole injecting layer and the hole transporting layer each contain an electron transporting material having electron transporting properties
Implementation Method 3
electrons are injected into the light emitting layer from the cathode side and also holes are injected thereinto from the anode side, so that the electrons and the holes are recombined in the light emitting layer to generate excitons, and when the excitons return to the ground state, the energy of the excitons is emitted as light
Data Source
AI summary
A light emitting element has an anode, a cathode, a light emitting layer which is provided between the anode and the cathode and emits light by energizing the anode and the cathode, and a functional layer (a hole injecting layer and a hole transporting layer) which is provided between the anode and the light emitting layer in contact therewith and has a function of transporting a hole, in which the hole injecting layer and the hole transporting layer each are constituted including an electron transporting material having electron transporting properties. The content of the electron transporting material contained in the hole injecting layer and the content thereof contained in the hole transporting layer are different from each other.