Asymmetric A-D-D′-A Organic Photovoltaic Acceptor
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Solution Overview
Problem
Current structurally simple small molecule photovoltaic acceptor materials in organic solar cells have low photovoltaic conversion efficiency and high energy loss due to their symmetric structures and the presence of a central carbon-carbon single bond, which affects photostability and electron mobility.
Innovation Solution
An asymmetric organic photovoltaic acceptor material in the A-D-D′-A type is synthesized using a noncovalent conformational lock strategy, introducing an alkoxy group onto the benzene ring of indenothiophene to form a noncovalent conformational lock with the thiophene ring of dithienocyclopentadiene, enhancing solubility, energy level tuning, and crystallization, thereby improving photovoltaic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If symmetric A-D-C-D-A type small molecule acceptor materials are used, then structural simplicity is achieved, but photovoltaic conversion efficiency remains low (10-14%) and energy loss is high
Solution Approach 1:
The patent applies asymmetry by designing an A-D-D'-A type molecular structure where the two donor units (D and D') are different. Specifically, one donor unit contains indenothiophene with alkoxy groups while the other contains dithienocyclopentadiene, creating an asymmetric architecture that breaks the symmetry of conventional A-D-C-D-A structures. This asymmetry optimizes charge separation and reduces energy loss while maintaining structural simplicity.
Solution Approach 2:
The patent implements local quality by introducing alkoxy groups (methoxy, ethoxy, or propoxy) at specific positions on the indenothiophene unit. These localized functional groups modify electron density distribution, enhance solubility, and improve photovoltaic performance without requiring complete structural redesign of the entire molecule.
2Stability of the object's composition
If dithienocyclopentadiene (DTC) units are used in symmetric structures, then material stability is improved, but photostability deteriorates and synthesis cost increases
Solution Approach 1:
The asymmetric A-D-D'-A structure distributes DTC units non-symmetrically, with one DTC-containing donor unit paired with an indenothiophene unit. This asymmetric arrangement reduces the formation of harmful H-aggregates that occur in symmetric structures, thereby improving photostability while maintaining compositional stability.
Solution Approach 2:
The indenothiophene unit acts as an intermediary between the acceptor and DTC-containing donor, mediating the interaction and reducing direct DTC-DTC contact that leads to photodegradation. This intermediary structure maintains material stability while protecting against photostability issues.
3Shape
If a central carbon-carbon single bond (C unit) is present in A-D-C-D-A structures, then structural symmetry is achieved, but electron mobility is reduced and photovoltaic performance deteriorates
Solution Approach 1:
The patent eliminates the central C unit by adopting an A-D-D'-A architecture without a central nucleus. The direct connection between donor units creates a more efficient π-electron delocalization pathway, enhancing electron mobility and photovoltaic performance while avoiding the H-aggregation problems associated with central C units in symmetric structures.
Solution Approach 2:
The molecular structure is segmented into distinct functional units (acceptor, donor1, donor2) connected through direct bonds without a central nucleus. This segmentation allows each unit to contribute optimally to electron transport while maintaining overall molecular planarity and π-conjugation.
4Device complexity
If simple condensed ring structures (≤3 rings) are used, then structural simplicity is achieved, but photovoltaic conversion efficiency lags behind large condensed ring structures (>3 rings)
Solution Approach 1:
The asymmetric A-D-D'-A structure with simple condensed rings achieves enhanced photovoltaic efficiency through optimized electronic structure. The asymmetry creates favorable energy level alignment and charge separation without requiring extensive ring condensation, thus maintaining structural simplicity while improving productivity.
Solution Approach 2:
The patent optimizes key parameters including HOMO/LUMO energy levels, band gap, and molecular planarity through the asymmetric design. These parameter changes enable simple condensed ring structures to achieve photovoltaic conversion efficiencies comparable to or exceeding those of larger condensed ring structures.
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 asymmetric A-D-D′-A type organic photovoltaic acceptor material achieves improved photovoltaic performance by maintaining molecular coplanarity, expanding π-electron delocalization, and balancing open-circuit voltage and short-circuit current, leading to higher efficiency and stability in organic solar cells.
Implementation Method 1
introducing an alkoxy group onto the benzene ring of indenothiophene, which then forms a noncovalent conformational lock with the thiophene ring of dithienocyclopentadiene
Implementation Method 2
asymmetric organic photovoltaic acceptor material in an A-D-D′-A type and use... achieves improved photovoltaic performance... leading to higher efficiency and stability in organic solar cells
Data Source
AI summary
An asymmetric organic photovoltaic acceptor material in an A-D-D′-A type is provided. A backbone containing noncovalent conformational lock is co-constructed with alkoxyindenothiophene and cyclopentadithiophene two-electron donor (D-D′) unit, and the ends are modified with fluorine- and chlorine-atom-substituted 3-(dicyanomethylidene)inden-1-one. The acceptor containing only a simple condensed ring has multiple advantages such as a coplanar backbone, low energy disorder, and J-aggregation tendency, and this type of asymmetric small-molecule acceptor has a controllably adjustable optical bandgap in the range of 1.30-1.45 eV, which is capable of combining with most donor materials to construct highly efficient binary bulk heterojunction organic solar cell. When the donor material is polymer PM6, the photoelectric conversion efficiency of the binary organic solar cells (OSCs) device is as high as 13.67%, with an open-circuit voltage (Voc) of 0.85 eV and energy loss (Eloss) is only 0.50 V.