Stacked Light-Emitting Layers for High Current Efficiency
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Solution Overview
Problem
Current light-emitting elements with organic compounds face challenges in achieving high current efficiency, leading to high power consumption, which hinders their mass production and application in next-generation flat panel displays.
Innovation Solution
A light-emitting element with a stacked structure of multiple light-emitting layers, including a first and second light-emitting layer with specific host and guest materials, where the emission peak of the second light-emitting layer is at a shorter wavelength than the first, and a charge-generation layer is introduced between these layers to enhance carrier injection and recombination efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional single light-emitting layer structure is used, then the device structure is simple, but the current efficiency is low leading to high power consumption
Solution Approach 1:
The light-emitting layer is divided into multiple stacked light-emitting layers (first light-emitting layer and second light-emitting layer), each with different emission peaks. This segmentation allows independent optimization of each layer's materials and properties to improve overall current efficiency while managing the increased structural complexity through systematic design.
Solution Approach 2:
Each light-emitting layer uses composite materials consisting of host materials and guest materials with specifically matched HOMO and LUMO levels. The first light-emitting layer uses a first host material and first guest material, while the second light-emitting layer uses a second host material and second guest material, creating a composite structure that optimizes charge carrier injection and recombination for enhanced current efficiency.
2Reliability
If host and guest materials with arbitrary energy levels are used, then material selection is flexible, but carrier injection and recombination efficiency is low
Solution Approach 1:
The invention specifies precise parameter ranges for HOMO and LUMO levels of host and guest materials. The HOMO level of the first host material is 5.0-6.5 eV, the LUMO level is 2.0-3.5 eV, and the HOMO level of the second host material is 4.5-6.0 eV with LUMO level 1.5-3.0 eV. These parameter constraints ensure optimal carrier injection and recombination efficiency while maintaining controlled material selection flexibility within the defined ranges.
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 proposed structure significantly improves current efficiency, reducing power consumption and enabling the development of low-power consumption light-emitting devices, including electronic and lighting devices with enhanced emission characteristics.
Implementation Method 1
an organic compound capable of emitting light by application of an electric field is provided between a pair of electrodes
Implementation Method 2
electrons injected from the cathode and holes injected from the anode recombine in the light emission center of the EL layer to form molecular excitons, and energy is released and light is emitted when the molecular excitons return to the ground state
Data Source
AI summary
A light-emitting element with a high current efficiency is provided. A low-power consumption light-emitting device is also provided. In addition, low-power consumption electronic device and lighting device are provided. The light-emitting element includes an EL layer between a pair of electrodes. The EL layer includes a light-emitting layer. The light-emitting layer includes a first light-emitting layer and a second light-emitting layer. The emission peak of the second light-emitting layer is at a shorter wavelength than that of the first light-emitting layer. The first light-emitting layer includes a host material and a guest material. The LUMO level of the guest material is in the range of ±0.1 eV of the LUMO level of the host material.