Organic EL Element Drive Life via Potential Gradient
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to extend the drive life of organic electroluminescence (EL) elements, which currently face limitations in longevity despite improvements in luminescence efficiency and reduced driving voltage.
Innovation Solution
The organic EL element incorporates a luminescence layer with a host material and luminescence pigment, where the oxidation and reduction potentials of the pigment are lower than those of the host, and the film thickness of the electron transport layer is greater than or equal to that of the hole transport layer, optimizing the recombination of electrons and holes to prevent deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescence material is used for the luminescence layer to improve luminescence efficiency, then luminescence efficiency is improved, but drive life is shortened
Solution Approach 1:
The invention changes the electrochemical parameters (oxidation and reduction potentials) of the luminescence pigment relative to the host material. Specifically, the luminescence pigment is selected to have both lower oxidation potential and lower reduction potential than the host material, creating a potential gradient that prevents charge accumulation and extends drive life while maintaining high luminescence efficiency through phosphorescence material
Solution Approach 2:
The host material acts as an intermediary between the luminescence pigment and the charge carriers. The host material with intermediate potential values facilitates efficient energy transfer to the luminescence pigment while the potential difference prevents direct charge accumulation on the pigment, thereby protecting the luminescence layer and extending drive life
2Duration of action of stationary object
If electron transport layer thickness is increased to prevent charge accumulation, then drive life is extended, but device structure becomes more complex
Solution Approach 1:
The invention uses parameter changes in the electrochemical potentials of the luminescence pigment relative to the host material to achieve charge balance. By selecting a pigment with both lower oxidation and reduction potentials than the host, the system creates intrinsic potential gradients that guide charge transport, eliminating the need for complex thickness adjustments and simplifying the device structure while extending drive life
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 effectively prolongs the drive life of the organic EL element by preventing unnecessary charge accumulation and reducing degradation, as evidenced by improved operational lifetimes in comparative testing.
Implementation Method 1
an organic electroluminescence (hereinafter referred to as EL) element emitting light on a luminescence layer by injecting electrons and holes
Implementation Method 2
phosphorescence that emits luminescence by returning from the triplet state to the ground states
Data Source
AI summary
Disclosed is an organic electroluminescent device having a longer drive life. Specifically disclosed is an organic electroluminescent device (100) comprising an organic material layer (16), which is composed of a hole transporting layer (164), a light-emitting layer (166) and an electron transporting layer (167), between a pair of electrodes, namely a cathode (18) and an anode (12). The light-emitting layer (166) (having a film thickness (dM) of 5-3000 nm) contains a luminescent dye and a host material. The first oxidation potential (ED+) of the luminescent dye is lower than the first oxidation potential (EH+) of the host material, while the first reduction potential (ED−) of the luminescent dye is lower than the first reduction potential (EH−) of the host material. The film thickness (dE: 5-3000 nm) of the electron transporting layer (167) and the film thickness (dH: 5-3000 nm) of the hole transporting layer (164) satisfy the following relation: dH≦dE.