Light Emitting Element Intermediate Layer Band Gap Optimization
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Solution Overview
Problem
Existing organic electroluminescence (EL) display devices face challenges in achieving high luminance due to insufficient suppression of light emission from the intermediate layer.
Innovation Solution
A light emitting element configuration with at least two light emitting layers of different colors and an intermediate layer containing a first organic material with hole transport properties and a second organic material with electron transport properties, where the band gap energy difference between the first organic material and the material with the maximum band gap energy among the light emitting layers is greater than or equal to 0.2 eV, optimizing energy transfer and reducing unnecessary light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an intermediate layer is used in organic EL display devices, then device structure is improved, but light emission efficiency deteriorates due to insufficient suppression of light emission from the intermediate layer
Solution Approach 1:
The patent applies parameter changes by carefully selecting the band gap energies of materials in the intermediate layer and light emitting layers. Specifically, the band gap energy of the first organic material in the intermediate layer is set to be 0.2 eV or more lower than the maximum band gap energy among materials in adjacent light emitting layers. This parameter optimization prevents energy transfer to the intermediate layer, suppressing unwanted light emission while maintaining the structural benefits of the intermediate layer.
Solution Approach 2:
The patent uses composite materials by combining a hole transporting material and an electron transporting material in the intermediate layer. This composite structure enables the intermediate layer to function as both a charge transport pathway and an energy barrier, preventing energy transfer to the light emitting layers while maintaining efficient charge transport.
2Ease of operation
If the intermediate layer contains both hole transporting and electron transporting materials, then charge transport is improved, but unwanted light emission from the intermediate layer increases
Solution Approach 1:
The patent resolves this contradiction by changing the energy parameter (band gap energy) of the materials. By setting the band gap energy of the first organic material to be 0.2 eV or more lower than the maximum band gap energy of adjacent light emitting layer materials, the intermediate layer becomes an energy barrier that prevents excitation and light emission, while still allowing efficient charge transport due to the presence of both hole and electron transporting materials.
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 the efficiency and longevity of the light emitting element by suppressing unnecessary energy transfer and charge accumulation, leading to improved luminance and extended life of the display device.
Implementation Method 1
an organic electroluminescence (EL) element as a light emitting element has been developed
Implementation Method 2
suppressing unnecessary energy transfer and charge accumulation
Data Source
AI summary
A light emitting element (10) of the present disclosure includes at least a first electrode (31), a second electrode (32), and a light emitting unit (30) sandwiched between the first electrode (31) and the second electrode (32), the light emitting unit 30 at least includes at least two light emitting layers (33a, 33b) that emit different colors and an intermediate layer (33d) located between the two light emitting layers (33a, 33b), the intermediate layer (33d) includes a first organic material (33e) having hole transport properties and a second organic material 33f having electron transport properties, and when a band gap energy of the first organic material (33e) is BGHTM and a band gap energy of a material having a maximum band gap energy among materials constituting two adjacent light emitting layers (33a, 33b) is BGmax, BGHTM-BGmax ≥ 0.2 eV is satisfied.