Organic Electroluminescence Device Electron Transporting Layer
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Solution Overview
Problem
The service life of organic electroluminescence devices is compromised due to the small atomic or molecular weight of alkali group metals and metal compounds used in electron injection and transporting layers, which affects the stability and efficiency of the devices.
Innovation Solution
An organic electroluminescence device structure incorporating an electron transporting layer with a first material having a monocyclic or polycyclic ring with an N-containing six-membered ring and a second material with a five-membered hetero ring, both being organic and metal-free, with a dipole moment difference to enhance electron injection and transport characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkali group metals and metal compounds (Li, Ca, LiF, LiQ) are used in electron injection and transporting layers, then electron injection characteristics are improved, but service life is reduced due to small atomic/molecular weight causing material movement
Solution Approach 1:
The patent changes the fundamental parameter of material composition by completely eliminating alkali metals and metal compounds from the electron transporting layer. Instead, it uses organic compounds with specific molecular structures (N-containing six-membered rings combined with five-membered hetero rings containing N, O, or S) that provide both excellent electron injection characteristics and long-term stability, thereby resolving the contradiction between improved electron injection and extended service life.
Solution Approach 2:
The patent employs composite organic materials combining N-containing six-membered rings (such as pyridine, pyrimidine, triazine) with five-membered hetero rings (such as imidazole, oxazole, thiazole) or cyano groups. This composite molecular structure achieves synergistic effects: the N-containing six-membered ring provides electron transporting capability while the five-membered hetero ring enhances electron injection characteristics, all without using problematic alkali metals.
2Productivity
If materials with larger band gap and deep HOMO level are used in electron transporting layer, then element efficiency is improved by blocking holes, but device complexity increases
Solution Approach 1:
The patent applies local quality by designing electron transporting materials with specific functional groups positioned at particular locations within the molecular structure. The N-containing six-membered ring provides hole-blocking capability with appropriate HOMO level, while the five-membered hetero ring or cyano group enhances electron injection. This localized functional group arrangement achieves both hole blocking and electron injection without requiring complex multi-layer structures.
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 results in an organic electroluminescence device with improved efficiency, longer service life, and reduced manufacturing complexity, achieving low driving voltage and high light emitting efficiency.
Implementation Method 1
an electron transporting layer provided between the cathode and the light emitting layer... the electron transporting layer includes a first electron transporting material and a second electron transporting material
Implementation Method 2
An organic electroluminescence device is an electric element which emits light through the current by an applied voltage
Data Source
Figure 1
AI summary
An exemplary embodiment of the present specification provides an organic electroluminescence device including: an anode; a cathode; a light emitting layer provided between the anode and the cathode; and an electron transporting layer provided between the cathode and the light emitting layer, in which the electron transporting layer includes a first electron transporting material and a second electron transporting material, the first electron transporting material is an organic material including a monocyclic or polycyclic ring which includes an N-containing six-membered ring, the second electron transporting material is an organic material including a five-membered hetero ring which includes at least one heteroatom of N, O, and S, or a cyano group, and a dipole moment of the second electron transporting material is larger than a dipole moment of the first electron transporting material.