Organic Light-Emitting Device Using nπ* Transition for High Efficiency
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Solution Overview
Problem
Conventional delayed fluorescent materials for organic light-emitting devices achieve light emission efficiencies within expected limits, and there is a need for materials that exceed these limits and provide higher light emission efficiency.
Innovation Solution
An organic light-emitting device utilizing a compound with a lone electron pair and π electron orbital, which undergoes inverse intersystem crossing from an excited triplet state to a singlet state, emitting fluorescent light efficiently, with specific energy level configurations and structural features such as a heptazine derivative, used as a light-emitting dopant or assist dopant in the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional delayed fluorescent materials are used, then the device can achieve light emission, but the light emission efficiency remains within expected limits and cannot exceed conventional thresholds
Solution Approach 1:
The patent changes the fundamental parameters of the light-emitting material by using nπ* transition compounds instead of conventional ππ* transition materials. This parameter change in the electronic transition type enables inverse intersystem crossing from triplet to singlet state, achieving light emission efficiency exceeding conventional limits while maintaining material stability
Solution Approach 2:
The patent employs composite material strategy by combining the nπ* transition compound (compound 1) with host materials (mCP, TCTA, BCP) to create a functional light-emitting layer. This composite approach allows the unique nπ* compound to provide high efficiency while the host materials provide structural support and charge transport, resolving the limitation of conventional single-material systems
2Use of energy by moving object
If nπ* transition mechanism is employed, then light emission efficiency exceeds conventional limits, but the device complexity increases due to novel mechanism requirements
Solution Approach 1:
The nπ* transition compound serves multiple functions simultaneously: it acts as the light-emitting dopant, the triplet state reservoir for inverse intersystem crossing, and the fluorescent emitter. This multi-functionality reduces the need for separate specialized materials, simplifying the overall device structure despite the novel mechanism
Solution Approach 2:
The patent uses the nπ* transition compound as an intermediary that facilitates the conversion from non-emissive triplet excitons to emissive singlet excitons through inverse intersystem crossing. This intermediary mechanism allows efficient energy utilization without requiring complex device architectures, achieving high external quantum efficiency of 6.0% with a relatively simple five-layer structure
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 device achieves enhanced light emission efficiency by emitting fluorescent light through the nπ* transition mechanism, exceeding conventional efficiencies with an external quantum efficiency of 6.0%, significantly improving light emission performance.
Implementation Method 1
when at least a part of electrons constituting the lone electron pair is excited to an excited triplet state 3nπ* through nπ* transition
Implementation Method 2
the part of electrons undergoes inverse intersystem crossing from the excited triplet state 3nπ* to an excited singlet state 1nπ*
Data Source
AI summary
An organic light-emitting device containing a compound having a lone electron pair and a π electron orbital, the compound emitting fluorescent light by such a mechanism that when at least a part of electrons constituting the lone electron pair is excited to an excited triplet state 3nπ* through nπ* transition, the part of electrons undergoes inverse intersystem crossing from the excited triplet state 3nπ* to an excited singlet state 1nπ*, and returns from the excited singlet state 1nπ* to the ground state, at which the fluorescent light is emitted. The organic light-emitting device has a high light emission efficiency.