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Alkyl-Side-Chain Engineering of Nonfused Nonfullerene Acceptors with Simultaneously Improved Material Solubility and
Taeho Lee1, Chang Eun Song2, Sang Kyu Lee2
1Department of Chemistry, Kyonggi University, 154-42 Gwanggyosan-ro, Yeongtong-gu, Suwon 16227, Republic of Korea.
New nonfullerene small molecules were developed for organic solar cells (OSCs). Alkyl side-chain engineering in TBTT-BORH and TBTT-ORH improved solubility and device performance, achieving 8.33% power conversion efficiency.
Area of Science:
- Materials Science
- Organic Electronics
- Photovoltaics
Background:
- Nonfullerene small molecules are crucial electron acceptors in organic solar cells (OSCs).
- Tailoring molecular structure, specifically alkyl side chains, significantly impacts film morphology, solubility, and device performance.
- Balancing material properties like solubility and crystallinity is key for efficient OSCs.
Purpose of the Study:
- To develop novel nonfullerene small molecules, TBTT-BORH and TBTT-ORH, for OSC applications.
- To investigate the influence of different alkyl side chains (butyloctyl vs. octyl) on molecular aggregation, solubility, and film properties.
- To optimize OSC performance through alkyl side-chain engineering and solvent-vapor annealing (SVA) treatment.
Main Methods:
- Synthesis of two nonfullerene small molecules: TBTT-BORH and TBTT-ORH.
- Characterization using differential scanning calorimetry and UV-vis absorption spectroscopy.
- Fabrication and testing of OSC devices using PTB7-Th as the polymer donor.
- Application of solvent-vapor annealing (SVA) treatment to improve film morphology.
Main Results:
- TBTT-ORH showed stronger molecular aggregation than TBTT-BORH.
- TBTT-BORH exhibited improved material solubility due to the butyloctyl group.
- SVA treatment enhanced the film morphology and packing of TBTT-BORH.
- The best OSC device, using SVA-treated TBTT-BORH, achieved a power conversion efficiency of 8.33% with a high open-circuit voltage of 1.02 V.
- SVA treatment improved charge-carrier mobility and short-circuit current density in TBTT-BORH devices.
Conclusions:
- Alkyl side-chain engineering is effective in tuning the properties of nonfullerene acceptors for OSCs.
- Solvent-vapor annealing is a viable method to enhance the performance of less aggregated materials like TBTT-BORH.
- Simultaneous improvement in material solubility and device performance was achieved by balancing molecular design and processing.
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