Organic Light-Receiving Element with Reverse Intersystem Crossing
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Solution Overview
Problem
In photoelectric conversion layers with bulk heterojunctions, the energy difference between donor and acceptor molecules leads to insufficient charge separation and open circuit voltage, and the interface area between these molecules is limited, affecting charge separation efficiency.
Innovation Solution
An organic light-receiving element with organic semiconductor molecules that enable reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state, allowing for direct and indirect charge separation, and incorporating a host molecule to suppress efficiency loss, along with a charge block layer and transport layers to facilitate charge movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk heterojunction is employed with donor and acceptor molecules, then photoelectric conversion can occur, but charge separation becomes insufficient due to energy difference requirements
Solution Approach 1:
The patent changes the energy level parameters by introducing triplet states with energies carefully positioned relative to singlet states. By controlling the energy difference between triplet and singlet states (making it smaller than thermal energy at operating temperature), the system enables efficient charge separation without requiring large energy differences between donor and acceptor molecules, thus resolving the contradiction between charge separation efficiency and energy requirements.
Solution Approach 2:
The patent employs composite organic semiconductor materials that incorporate both singlet and triplet state functionalities within the same material system. This composite approach allows the material to utilize multiple energy pathways (direct singlet-to-charge separation and triplet-to-charge separation via reverse intersystem crossing), thereby improving charge separation efficiency without increasing the overall energy difference requirement.
2Reliability
If donor and acceptor molecules are mixed to form bulk heterojunction, then photoelectric conversion occurs, but interface area decreases affecting charge separation
Solution Approach 1:
The patent segments the charge separation process into multiple independent pathways: direct charge separation from singlet states and charge separation from triplet states via reverse intersystem crossing. This segmentation allows charge separation to occur at multiple sites and through multiple mechanisms within the bulk material, effectively compensating for the reduced interface area that would result from simple donor-acceptor mixing.
Solution Approach 2:
The triplet state acts as an intermediary energy level that mediates charge separation. By introducing this intermediate state with appropriate energy positioning, the system enables charge separation to proceed through a two-step process (excitation to triplet state, then reverse intersystem crossing to singlet state followed by charge separation), thereby maintaining high charge separation efficiency even when direct donor-acceptor interface area is limited.
3Power
If large energy difference is ensured between donor and acceptor molecules, then open circuit voltage increases, but charge separation becomes insufficient
Solution Approach 1:
The patent fundamentally changes the energy level parameters by utilizing triplet states with energies that are closer to the ground state than traditional acceptor molecules. By making the triplet-singlet energy difference smaller than thermal energy (kT), the system achieves both high open circuit voltage and efficient charge separation simultaneously, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent ensures continuous useful action by enabling both direct charge separation from singlet states and charge separation from triplet states via reverse intersystem crossing. This dual pathway mechanism ensures that every excited molecule contributes to charge separation, maximizing both power output and charge separation efficiency without compromise.
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 sufficient charge separation and improved photoelectric conversion efficiency by extending the lifetime of the triplet state and reducing energy requirements for charge separation, while also allowing for efficient charge detection and potential memory functionality.
Implementation Method 1
an excited state enabling reverse intersystem crossing from a lowest excited triplet state to a lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules due to irradiation with light
Implementation Method 2
A bulk heterojunction is typically employed in a photoelectric conversion layer composed of an organic semiconductor material
Data Source
AI summary
An organic light-receiving element includes an organic light-receiving layer containing a plurality of organic semiconductor molecules. Each of the plurality of organic semiconductor molecules is a molecule in which an excited state enabling reverse intersystem crossing from a lowest excited triplet state to a lowest excited singlet state is formed in each of the plurality of organic semiconductor molecules due to irradiation with light.