Intramolecular Singlet Fission Polymers for Solar Cell Efficiency
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Solution Overview
Problem
Current organic solar cells are limited by the Shockley-Queisser limit, which restricts their efficiency to 33.7%, and there is a lack of understanding and design rules for intramolecular singlet fission in polymeric materials, hindering the development of efficient solar cells capable of multiple exciton generation.
Innovation Solution
Design of organic compounds with strong intrachain donor-acceptor interactions and charge-transfer states that mediate the population transfer between singlet and triplet excitons, allowing for efficient intramolecular singlet fission, achieving triplet yields of up to 200% and enabling the development of tunable materials for solar cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional organic solar cell materials are used, then the device structure is simple and ease of manufacture is maintained, but the power conversion efficiency is limited to 33.7% due to the Shockley-Queisser limit
Solution Approach 1:
The patent changes the fundamental energy conversion parameters by introducing materials with specific singlet-triplet energy gap characteristics. The key parameter change is ensuring that the triplet energy (ET) is approximately half of the singlet energy (ES), enabling efficient singlet fission that generates multiple excitons from single photons, thereby exceeding the conventional Shockley-Queisser efficiency limit while maintaining solution processability
Solution Approach 2:
The patent employs composite material design by combining donor and acceptor components in bulk heterojunction structures. The donor material is specifically designed to undergo efficient singlet fission, while the acceptor material facilitates charge separation. This composite approach enables multiple exciton generation while maintaining the ease of manufacture through solution processing and standard device fabrication techniques
2Productivity
If intermolecular singlet fission is used, then multiple exciton generation can occur, but well-oriented crystalline materials are required which increases manufacturing complexity
Solution Approach 1:
The patent introduces charge-transfer (CT) states as intermediary mechanisms that mediate the singlet fission process. By designing materials where CT states play a role in the singlet fission mechanism, the process can proceed without requiring strict molecular orientation or crystalline structures. The CT states act as intermediaries that facilitate exciton generation in more disordered, solution-processed materials
Solution Approach 2:
Instead of requiring materials to be crystalline and well-oriented to achieve intermolecular singlet fission, the patent inverts the approach by designing intramolecular singlet fission capabilities within polymer chains. This inversion allows multiple exciton generation in amorphous, solution-processable materials, fundamentally reversing the traditional requirement for crystalline order
3Ease of manufacture
If intramolecular singlet fission is implemented in polymers, then solution processability improves, but the mechanism is not well understood and design rules are lacking
Solution Approach 1:
The patent establishes specific parameter guidelines for intramolecular singlet fission in polymers: (1) the triplet energy ET should be approximately half of the singlet energy ES, (2) the lowest lying optical excitation should have significant charge-transfer character, and (3) strong intrachain donor-acceptor interactions should be present. These parameter specifications provide actionable design rules that guide material development while maintaining solution processability
4Productivity
If strong intrachain donor-acceptor interactions are designed, then triplet yields can reach 200%, but the material design complexity increases
Solution Approach 1:
The patent segments the polymer structure into distinct donor and acceptor units that alternate along the chain. This segmentation creates localized regions of strong intrachain donor-acceptor interactions without requiring complex overall material design. The modular nature of segmented structures allows systematic optimization of triplet yield while managing design complexity through repeatable structural units
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 approach enables the creation of materials with high triplet yields, overcoming the efficiency limitations of traditional solar cells and providing a pathway for improving the power conversion efficiency beyond the Shockley-Queisser limit.
Implementation Method 1
intramolecular singlet fission (iSF), the latter generally being considered more useful for implementation into devices
Implementation Method 2
with significant charge-transfer (CT) character that can act to mediate the SF process
Implementation Method 3
Solar cells, also known as photovoltaic cells, are electrical devices that convert light energy directly into electricity by, what is known as, the photovoltaic effect
Data Source
AI summary
Embodiments of the present invention provides compounds, compositions, and methods for their preparation that provide efficient intramolecular fission, such that local order and strong nearest neighbor coupling is no longer a design constraint. Inventive materials include organic oligomers and polymers designed to exhibit strong intrachain donor-acceptor interactions and provide intramolecular singlet fission, whereby triplet populations can be generated in very high yields of, e.g., 170% or more. The inventive disclosure is directed to polymers of the general formula: [SA-SD]n with a strong electron acceptor (SA), a strong electron donor (SD), and n a positive integer equal to or greater than two; methods for their preparation and monomers used therein, blends, mixtures and formulations containing them; the use of the polymers, blends, mixtures and formulations as semiconductors in organic electronic (OE) devices, especially in organic photovoltaic (OPV) devices, and to OE and OPV devices comprising these polymers, blends, mixtures or formulations.