Exciton Confinement Layer Optimizes OLED Driving Voltage and Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic electroluminescent devices face challenges in achieving low driving voltage, high luminous efficiency, and long lifespan, particularly due to limitations in exciton confinement and the efficiency of phosphorescent dopants for blue phosphorescent devices, as well as instability from hole diffusion into electron transporting layers.
Innovation Solution
An organic electroluminescent device structure is developed with an exciton confinement layer in the electron transporting area, where the density of states is adjusted to overlap with adjacent layers, enhancing carrier mobility and exciton confinement, thereby reducing driving voltage and improving efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent dopants with deep blue color purity and high efficiency are used, then luminous efficiency is improved, but device complexity increases due to insufficient development of suitable dopants and hosts
Solution Approach 1:
The patent introduces an exciton confinement layer as an intermediary component between the emissive layer and electron transporting layer. This layer mediates the interaction between electrons and holes, confining excitons to the emissive layer to enhance recombination efficiency and luminous efficiency without requiring complex phosphorescent dopant systems.
Solution Approach 2:
The patent adjusts the density of states (DOS) parameter of the exciton confinement layer to optimize exciton confinement. By controlling the DOS overlap between adjacent layers, the device achieves high luminous efficiency through parameter optimization rather than relying on complex dopant chemistry.
2Measurement precision
If high resolution is achieved by forming more pixels in the same area, then display resolution is improved, but light emitting area decreases resulting in reduced lifetime
Solution Approach 1:
The patent optimizes the density of states parameter of the exciton confinement layer to enhance carrier mobility and exciton confinement efficiency. This allows smaller pixel sizes with sufficient light emission intensity, enabling high resolution displays with adequate lifetime by improving the efficiency of each pixel rather than relying on larger pixel areas.
3Device complexity
If holes diffuse into electron transporting layer, then device structure is simplified, but device stability deteriorates
Solution Approach 1:
The exciton confinement layer serves as an intermediary barrier between the hole transporting layer and electron transporting layer. It prevents harmful hole diffusion into the electron transporting layer while maintaining device structure simplicity, thus improving stability without adding complex multi-layer structures.
Solution Approach 2:
The patent converts the potential harmful effect of hole diffusion into a beneficial exciton confinement mechanism. By designing the exciton confinement layer with appropriate density of states, holes that would otherwise diffuse harmfully are instead utilized to form confined excitons that enhance light emission efficiency.
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
The device achieves low driving voltage and high luminous efficiency by confining excitons effectively, increasing the lifespan and stability of the organic electroluminescent device through optimized exciton confinement and carrier mobility.
Implementation Method 1
an exciton confinement layer in which a predetermined physical property is adjusted to a predetermined range is disposed in an area of the electron transporting area in contact with the emissive layer
Implementation Method 2
a density of states for LUMO (DOSLUMO ECL) of the exciton confinement layer satisfies at least one or more of the following conditions (i) and (ii): (i) the density of states for LUMO (DOSLUMO ECL) of the exciton confinement layer having a DOS that overlaps more than 0% of a density of states for LUMO (DOSLUMO HOST) of the host; and (ii) the density of states for LUMO (DOSLUMO ECL) of the exciton confinement layer having a DOS that overlaps more than 0% of a density of states for LUMO (DOSLUMO ET) of the remaining layer of the electron transporting area
Implementation Method 3
When the injected holes and electrons meet, an exciton is formed, and the exciton falls to the ground state, resulting in light emission
Data Source
AI summary
An organic electroluminescent device is disclosed. The organic electroluminescent device achieves low driving voltage and high luminous efficiency as well as long lifespan by including an exciton confinement layer (ECL), in which a predetermined physical property is adjusted, in an area of an electron transporting area, including at least two layers, that is adjacent to an emissive layer.