OLED Host Material Energy Transfer for Low Voltage
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Solution Overview
Problem
Existing organic electroluminescent elements face challenges in achieving low driving voltage and high emission efficiency due to carrier migration issues between light-emitting layers, often requiring increased driving voltage to maintain emission efficiency and lifetime.
Innovation Solution
A light-emitting element configuration with a first, second, and third light-emitting layer, each containing luminescent materials and host materials, where the first light-emitting layer has a longer wavelength and includes a second host material with a lower energy gap than the first host material, allowing efficient exciton energy transfer and migration, thereby reducing driving voltage and enhancing emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If different host materials are used in each light-emitting layer to optimize luminescence, then emission efficiency is improved, but carrier migration is limited at layer boundaries causing driving voltage to increase
Solution Approach 1:
The patent applies local quality by using different host materials in different regions (light-emitting layers) to optimize local luminescence properties, while introducing a common host material at the boundaries to ensure smooth carrier migration. Specifically, each light-emitting layer contains a host material optimized for its specific luminescent material, but adjacent layers share at least one common host material at their interface, creating a gradient transition that maintains both local optimization and global carrier transport.
Solution Approach 2:
The patent uses a common host material as an intermediary between different host materials in adjacent light-emitting layers. This intermediary host material facilitates carrier migration across layer boundaries by providing a continuous energy level pathway, preventing the carrier migration limitation that would occur with completely different host materials at each interface.
2Reliability
If interlayers are arranged between light-emitting layers to restrict carrier migration, then emission efficiency and lifetime are enhanced, but driving voltage increases
Solution Approach 1:
The patent extracts the carrier migration control function from separate interlayer structures and integrates it into the host material composition of the light-emitting layers themselves. By using common host materials at layer boundaries, the patent achieves carrier migration restriction without requiring additional interlayer components, thereby avoiding the voltage increase associated with extra layers.
Solution Approach 2:
The patent merges the functions of light emission and carrier migration control into a single integrated structure. The host materials in adjacent light-emitting layers are selected to overlap in energy levels, allowing the same material layer to serve both as the luminescence host and as the carrier migration pathway, eliminating the need for separate control interlayers.
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 configuration results in a light-emitting element with low driving voltage and high emission efficiency, enabling reliable operation and extended lifetime while maintaining balanced light emission across colors.
Implementation Method 1
The second host material is superior in enhancing the luminescence of the first light-emitting layer to the first host material
Implementation Method 2
the energy of the excitons is emitted in the form of light when the excitons return to the ground state
Implementation Method 3
host materials supporting the luminescent materials
Implementation Method 4
the electrons and the holes recombine with each other in the light-emitting layer to generate excitons
Data Source
AI summary
A light-emitting element includes a cathode; an anode; and a light-emitting section which is disposed between the cathode and the anode and which includes a first light-emitting layer, second light-emitting layer, and third light-emitting layer each containing a corresponding one of luminescent materials emitting light of different colors and host materials supporting the luminescent materials. The first, second, and third light-emitting layers commonly contain a first host material that is one of the host materials. The first light-emitting layer emits light of a first color having a longer wavelength as compared to light emitted from the second and third light-emitting layers and contains a second host material which is one of the host materials and which is different from the first host material. The second host material is superior in enhancing the luminescence of the first light-emitting layer to the first host material.