Light-Emitting Element Composite Material Charge Transfer
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Solution Overview
Problem
Light-emitting elements with an EL layer between electrodes face reduced lifetime due to increased current, which also lowers light extraction efficiency, as the EL layer deteriorates with higher luminance requirements.
Innovation Solution
A light-emitting element using a composite material with an organic compound and an electron acceptor, where charge-transfer interaction is minimized, ensuring high hole injection efficiency without forming charge-transfer complexes, thereby reducing absorption in the visible light region and increasing transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the amount of current supplied to the light-emitting element is increased to increase luminance, then the luminance is improved, but the lifetime of the light-emitting element is reduced due to accelerated deterioration of the EL layer
Solution Approach 1:
The light-emitting element is divided into multiple light-emissive units stacked between anode and cathode, with charge generation layers provided between the units. This segmentation allows the total luminance requirement to be distributed across multiple units, reducing the current burden on each individual unit and thereby extending lifetime while maintaining overall high luminance output.
Solution Approach 2:
Charge generation layers are introduced as intermediary layers between the light-emissive units. These layers facilitate charge transfer between units through oxidation-reduction reactions, enabling efficient current distribution and reducing the stress on individual EL layers, thus extending device lifetime while maintaining high luminance.
2Illumination intensity
If a charge generation layer containing a charge-transfer complex is used to increase luminance, then the luminance is improved, but the light extraction efficiency is reduced due to absorption in the visible light region
Solution Approach 1:
The patent modifies the optical parameters of the charge generation layer by selecting organic compounds and electron acceptors/donors whose charge-transfer complexes have absorption peaks in the near-infrared region (800-2000 nm) rather than in the visible light region. This parameter change allows the charge generation layer to maintain its charge transfer functionality while minimizing absorption of visible light, thereby improving light extraction efficiency alongside luminance enhancement.
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 enhances light extraction efficiency, reduces power consumption, and maintains high luminance while prolonging the element's lifetime by minimizing charge-transfer interaction and absorption in the visible light region.
Implementation Method 1
an electron acceptor having an electron-accepting property with respect to the organic compound
Implementation Method 2
holes generated through extraction of electrons from the organic compound by the electron acceptor on voltage application are injected from a layer containing the composite material into an adjacent layer
Implementation Method 3
light-emitting element having an EL layer between a pair of electrodes
Data Source
AI summary
Provided are a light-emitting element capable of reducing power consumption by increasing its light extraction efficiency and a light-emitting device using the light-emitting element. A light-emitting element includes a composite material, which contains an organic compound having a high hole-transport property and an electron acceptor and in which the spin density measured by an electron spin resonance (ESR) method is less than or equal to 1×1019 spins/cm3, the spin density is less than or equal to 3×1019 spins/cm3 when the molar ratio of the electron acceptor to the organic compound is greater than or equal to 1, or the spin density is less than or equal to 5×1019 spins/cm3 when the molar ratio is greater than or equal to 2.