Organic Electroluminescent Device Host Material Triplet Utilization
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Solution Overview
Problem
Traditional fluorescent materials in organic electroluminescent devices can only utilize 25% of singlet state excitons due to spin-forbidden transitions, resulting in limited external quantum efficiency, while attempts to utilize triplet state excitons, such as with phosphorescent materials, are costly due to the need for rare heavy metals.
Innovation Solution
A novel organic electroluminescent device with a light-emitting layer featuring a host material that utilizes charge-transfer transitions, where the triplet state energy level is higher than the n-π excited state, allowing for efficient energy transfer and full utilization of triplet state excitons without the need for noble metals, achieved by selecting materials with specific energy level differences and incorporating a fluorescent dye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent material with heavy atoms is used to utilize triplet state excitons, then internal quantum efficiency reaches 100%, but production cost increases due to expensive rare heavy metals
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing rare heavy metals with inexpensive fluorescent materials that have appropriate energy level structures. The fluorescent host material utilizes triplet state excitons through thermal activation to singlet states, achieving high efficiency without costly materials. This substitution directly addresses the cost issue while maintaining the efficiency benefit.
Solution Approach 2:
The patent changes the energy level parameters of the host material to enable triplet state utilization in fluorescent devices. Specifically, it selects host materials where the triplet state energy level (T1) is higher than the singlet state energy level (S1) by a controlled amount (0.1-0.5 eV), and where the energy difference between T1 and S0 allows thermal activation. This parameter optimization enables efficient triplet state utilization without phosphorescent materials.
2Ease of manufacture
If traditional fluorescent material is used, then production cost is low, but external quantum efficiency is limited to 5% due to spin-forbidden transitions
Solution Approach 1:
The patent modifies the energy level parameters of the fluorescent host material to enable triplet state utilization. By selecting materials where T1 > S1 by 0.1-0.5 eV and where the T1-S0 energy difference allows thermal activation, the device can convert non-emissive triplet excitons into emissive singlet states, dramatically improving external quantum efficiency from 5% to potentially 62.5% or higher while maintaining cost-effectiveness.
Solution Approach 2:
The patent converts the previously harmful waste heat from triplet state relaxation into a useful resource. By designing the energy level structure so that triplet states can be thermally activated to singlet states (which then emit light), the patent transforms the 75% of excitons that were previously lost as heat into a source of additional light emission, improving overall efficiency.
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 enables 100% internal quantum efficiency and reduces production costs by fully utilizing triplet state energy, outperforming previous methods while avoiding the use of expensive heavy metals.
Implementation Method 1
Host material in this light-emitting layer is special material with charge-transfer transition
Implementation Method 2
allowing for efficient energy transfer and full utilization of triplet state excitons
Implementation Method 3
When electro-excited, an organic electroluminescent device will generate 25% of singlet state and 75% of triplet state
Data Source
AI summary
The present invention discloses an organic electroluminescent device and a manufacturing method thereof. The host material of the light-emitting layer of the organic electroluminescent device is material in which the triplet state energy level of the CT excited state is higher than that of the n-π excited state by 0 to 0.3 eV; or the triplet state of the host material of the light-emitting layer is higher than that of the n-π excited state by more than 1.0 eV; in addition, the difference in energy level between the second triplet state of the n-π state and the first singlet state of the CT excited state is −0.1 to 0.1 eV; and the luminescent dye is a fluorescent dye. With regard to the organic electroluminescent device in the present invention, as new host material in the light-emitting layer is used and the host material has a donor group and an acceptor group, the triplet state in the light-emitting layer may be fully utilized to achieve a 100% light-emitting efficiency in the fluorescent device. Furthermore, no noble metal is required to be used, thus reducing the cost.