Organic EL Element Mixed Light-Emitting Layer Carrier Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional organic electroluminescent (EL) elements face challenges such as high drive voltage, carrier loss, and low productivity due to complex structures, and struggle with efficient light emission and luminous efficacy, particularly in tandem structures and multi-color light-emitting layer configurations.
Innovation Solution
The configuration of an organic EL element with a mixed light-emitting layer containing a luminescent host material and a dopant material, along with two or more luminescent dopant layers separated by a blocking layer, optimizes carrier recombination and prevents dopant material deactivation, enhancing luminous efficacy and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tandem structure with vertically separated emission positions is used, then carrier balance between electrons and holes is improved, but drive voltage increases and luminous efficacy decreases due to carrier loss in the middle layer
Solution Approach 1:
The patent merges the emission positions of multiple colors into a single plane by stacking light-emitting layers adjacent to each other horizontally. This eliminates the need for a middle layer between vertically stacked elements, thereby preventing carrier loss while maintaining good carrier balance. The light-emitting layers are arranged side-by-side rather than vertically separated, allowing carriers to recombine efficiently in each layer without traversing through intermediate layers.
Solution Approach 2:
The patent transitions from a vertical stacking arrangement (tandem structure) to a horizontal adjacent arrangement of light-emitting layers. This dimensional change allows multiple emission positions to coexist in the same vertical plane while eliminating the need for intermediate blocking layers, thus resolving the contradiction between carrier balance and luminous efficacy.
2Reliability
If a tandem structure with middle layer is used, then carrier balance is improved, but device complexity increases due to additional layers
Solution Approach 1:
The patent extracts and removes the middle layer from the tandem structure. By eliminating this intermediate layer, the device complexity is reduced while still achieving good carrier balance through the horizontal adjacent arrangement of light-emitting layers. Each light-emitting layer can be independently optimized without the constraint of requiring a middle layer for carrier management.
3Productivity
If light-emitting layers for respective colors are stacked adjacent to each other, then productivity is improved, but luminous efficacy decreases due to difficulty in controlling emission positions
Solution Approach 1:
The patent applies local quality by optimizing each adjacent light-emitting layer with specific host and dopant materials tailored to emit particular colors. Each layer is independently designed with appropriate material compositions and thicknesses to ensure efficient carrier recombination and light emission at its specific location, thereby maintaining high luminous efficacy while enabling adjacent stacking for improved productivity.
4Device complexity
If multiple luminescent dopant materials are contained in one light-emitting layer, then device complexity is reduced, but luminous efficacy decreases due to mutual deactivation of dopant materials
Solution Approach 1:
The patent segments the light-emitting layers into separate adjacent layers, each containing a single luminescent dopant material. This segmentation prevents mutual deactivation of dopant materials that would occur if multiple dopants were mixed in one layer. Each layer is independently optimized for its specific dopant, maintaining high luminous efficacy while the overall multi-layer structure achieves the desired color emission spectrum.
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 carrier barriers, achieves efficient light emission, and increases productivity by trapping carriers in specific dopant layers, resulting in high luminous efficacy and simplified manufacturing processes.
Implementation Method 1
Organic EL elements emit light by recombining holes injected from the anode and electrons injected from the cathode within a light-emitting layer disposed between these electrodes
Data Source
AI summary
The present invention provides an organic EL element with high luminous efficacy and high productivity, and an organic EL panel including the organic EL element. The organic electroluminescent element includes, in the given order: an anode; a hole transport layer; a light-emitting unit; an electron transport layer; and a cathode, the light-emitting unit including a first luminescent dopant layer, a first blocking layer, a second luminescent dopant layer, and a mixed light-emitting layer in the given order, the mixed light-emitting layer containing a first luminescent host material and a first luminescent dopant material, the first luminescent dopant layer substantially consisting of a second luminescent dopant material, the second luminescent dopant layer substantially consisting of a third luminescent dopant material, the first blocking layer containing a second luminescent host material.