Organic EL Light-Emitting Element with Gradient Assist Dopants
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In organic electroluminescence elements, the concentration of recombination sites for carriers leads to localized degradation of luminescent materials near the interface, resulting in accelerated deterioration of the light-emitting layer and insufficient control over carrier transportability.
Innovation Solution
A light-emitting element with multiple layers, each containing a luminescent material, a host material, and an assist dopant material, where the assist dopant materials are strategically chosen to control carrier transportability, ensuring balanced recombination sites and preventing hole passage to the cathode side, thereby extending the luminescence characteristics and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a host material containing an acene-based compound is used to provide high electron transportability, then carrier transportability is improved, but recombination sites become concentrated near the interface causing localized degradation and accelerated deterioration
Solution Approach 1:
The patent applies local quality by introducing assist dopant materials with different properties at different locations within the light-emitting layer. The first assist dopant material is introduced near the anode side while the second assist dopant material is introduced near the cathode side, creating spatially varying carrier transport characteristics that distribute recombination sites uniformly throughout the layer rather than concentrating them at the interface.
Solution Approach 2:
The assist dopant materials serve as intermediary substances that mediate between the host material and the luminescent material. These dopants modify the carrier transport properties of the host material locally, enabling precise control over where carriers recombine without changing the fundamental structure or composition of the entire light-emitting layer.
2Reliability
If assist dopant material is added to control carrier transportability, then recombination site distribution is improved, but device complexity increases due to multiple material components
Solution Approach 1:
The patent segments the assist dopant function into two distinct components: a first assist dopant material positioned near the anode and a second assist dopant material positioned near the cathode. This segmentation allows each dopant to be optimized for its specific location's carrier transport needs, providing precise control over recombination site distribution while maintaining a manageable level of complexity through functional division.
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 solution effectively spreads recombination sites across the light-emitting layers, reducing localized degradation and enhancing both luminescence efficiency and longevity of the organic electroluminescence element.
Implementation Method 1
carriers are recombined in the molecule of the host material to generate excitation energy, and this excitation energy is transferred to a luminescent material, thereby causing the luminescent material to emit light
Implementation Method 2
An organic electroluminescence element (so-called organic EL element) is a light-emitting element having a structure in which a luminescent organic layer of at least one layer is interposed between an anode and a cathode
Implementation Method 3
the recombination sites of carriers are determined by the carrier transportability of the host material used in the light-emitting layer
Implementation Method 4
the characteristics of the organic EL element are improved by controlling the relationship between HOMO and LUMO of the host material and the assist dopant material
Data Source
AI summary
Disclosed herein is a light-emitting element, including: a cathode; an anode; and a light-emitting unit, in which the light-emitting unit includes a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer, which are laminated from the anode side to the cathode side, in which each of the first, second, and third light-emitting layers is configured to contain a luminescent material, a host material, and an assist dopant material, and in which, when the contents of the assist dopant materials contained in the first, second, and third light-emitting layers are respectively expressed by CAssist(EML1), CAssist(EML2) and CAssist(EML3), the following Relational Expression (A) is satisfied:CAssist(EML1)≧CAssist(EML2)>CAssist(EML3)≧0 (A).