Organic EL Stacked Electron Transport Layer for Efficiency
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Solution Overview
Problem
Organic electroluminescent devices using dibenzimidazole derivatives exhibit high electron injection barriers and low electron mobility, leading to increased voltage and decreased luminous efficiency due to insufficient electron supply.
Innovation Solution
A stacked electron transport layer structure is implemented, with a dibenzimidazole derivative layer on the light-emitting layer side and a benzimidazole derivative layer on the cathode side, allowing for adjustable electron injection and optimizing the thickness of each layer to achieve necessary electron density for exciton formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a dibenzimidazole derivative is used as an electron transport layer material, then the device structure is simplified, but the electron injection barrier increases and electron mobility decreases
Solution Approach 1:
The electron transport layer is divided into two separate layers: a first electron transport layer containing a dibenzimidazole derivative and a second electron transport layer containing a benzimidazole derivative. This segmentation allows each layer to perform its specific function - the first layer provides structural stability while the second layer ensures efficient electron injection, thereby resolving the contradiction between structural simplicity and electron injection efficiency.
Solution Approach 2:
The patent uses a composite structure combining two different heterocyclic derivative materials (dibenzimidazole and benzimidazole) in a layered configuration. This composite approach leverages the complementary properties of each material - the dibenzimidazole derivative's structural characteristics and the benzimidazole derivative's superior electron injection capability - to achieve both structural integrity and high electron transport efficiency.
2Ease of manufacture
If a dibenzimidazole derivative is used as an electron transport layer material, then the manufacturing process is simplified, but the luminous efficiency decreases due to insufficient electron supply
Solution Approach 1:
By segmenting the electron transport layer into two functional layers, the patent enables the second layer (benzimidazole derivative) to specifically address electron supply requirements, thereby improving luminous efficiency without significantly complicating the overall manufacturing process.
Solution Approach 2:
The patent optimizes the thickness parameters of each layer - the first electron transport layer is set to 5-50 nm and the second electron transport layer to 5-30 nm. This parameter optimization ensures adequate electron supply to the light-emitting layer while maintaining manufacturing feasibility and controlling production complexity.
3Reliability
If only a benzimidazole derivative is used in the electron transport layer, then electron injection is improved, but electrons are excessively supplied to the light-emitting layer
Solution Approach 1:
The segmented layered structure allows the first electron transport layer (dibenzimidazole derivative) to act as a buffer that modulates the electron flow from the second layer. This segmentation enables precise control over electron supply to the light-emitting layer, preventing excessive electron injection while maintaining high electron transport efficiency.
Solution Approach 2:
Each layer is assigned a specific local function: the first layer (dibenzimidazole derivative) provides structural framework and moderate electron transport, while the second layer (benzimidazole derivative) provides enhanced electron injection capability. This local quality differentiation ensures optimal electron supply control to the light-emitting layer.
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 enhances luminous efficiency and extends the lifetime of organic electroluminescent devices, reducing electric power consumption and improving the long-term reliability of display apparatuses.
Implementation Method 1
an electron transport layer having a structure in which a layer containing a dibenzimidazole derivative and a layer containing a benzimidazole derivative are stacked
Implementation Method 2
Organic electroluminescent devices (organic EL devices) that use electroluminescence (hereinafter abbreviated as EL) of organic materials
Data Source
AI summary
An organic electroluminescent device includes an anode; a cathode; an organic layer including a light-emitting layer and disposed between the anode and the cathode; and an electron transport layer constituting the organic layer, disposed between the cathode and the light-emitting layer, and having a stacked structure including a layer containing a benzimidazole derivative and a layer containing a dibenzimidazole derivative represented by general formula (1):wherein Y1 to Y8 each represent a substituted or unsubstituted aryl group having 6 to 60 carbon atoms, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted quinolyl group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aliphatic cyclic group, and Y7 and Y8 may form a ring through a linking group.