Fluorinated polythiophenes with ester side chains for boosting the Voc and efficiency in non-fullerene polymer solar cells
Year: 2025
Type: article
Abstract: As the power conversion efficiency (PCE) of organic photovoltaics (OPVs) nears the 19% threshold, wide bandgap (WBG) polythiophenes (PTs) have gained increasing attention due to their simple chemical structures and ease of synthesis, making them promising candidates for large-scale production. However, the benchmark polymer poly(3-hexylthiophene) (P3HT) is limited by its high-lying HOMO energy level, which restricts the open-circuit voltage (VOC) in solar cells. In this study, we introduce a novel series of PT derivatives (PDC8T, PDC8TT, PDC16TT, and PDC16TF) featuring ester side chains designed to fine-tune electronic properties through a streamlined three-step synthesis. Additionally, we incorporated a p-spacer to reduce steric hindrance and elongated alkyl side chains to improve solubility and processability. Compared to P3HT, these PT derivatives demonstrate a significant reduction in HOMO energy levels, lowering by approximately 0.3 to 0.4 eV. Among them, PDC16TF—with fluorine atom substitution—achieves the lowest HOMO energy level, induces a coplanar molecular conformation, and enhances polymer aggregation behavior.We evaluated these PT derivatives in inverted non-fullerene bulk-heterojunction (NFA BHJ) OPVs. The PDC8TT device showed a relatively low PCE of 0.69%, with a VOC of 0.76 V, a short-circuit current density (JSC) of 3.32 mA cm-2, and a fill factor (FF) of 27.3%. In contrast, the PDC16TF device achieved an impressive PCE of 7.21%, with a VOCof 0.85 V, a JSC of 14.60 mA cm-2, and an FF of 58.4%. This remarkable improvement is attributed to the fluorine substitution, which not only enhances molecular orientation but also downshifts the HOMO energy level and further boosts the VOC. Hence, these molecular design strategies have led to a fibrillar bicontinuous interpenetrating network with optimal nanoscale phase separation within the active layer.
Source: Polymer
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,980
Funders: National Science and Technology Council, U.S. Department of Energy, Center for Integrated Nanotechnologies, Academia Sinica, Ministry of Science and Technology of the People's Republic of China, Ministry of Science and Technology, Taiwan, National Taiwan University, National Science and Technology Council, Office of Science, Los Alamos National Laboratory
Awards: Molecular Design and Synthesis of Conjugated Organic Compounds as Energy Materials, Development of Hole Transporting Polymers and Functionalized Graphene Oxide Nanosheets for Interfacial Modification to Improve Performance and Long-Term Stability of Perovskite Solar Cells, G1810987215, G2254516282, G3293605453, Development of Transforming Conventional Step-Growth Polycondensation to Living Chain-Growth Polymerization for the Synthesis of Well-Defined Hyperbranched Block Copolymers, Development of Hole Transporting Polymers and Functionalized Graphene Oxide Nanosheets for Interfacial Modification to Improve Performance and Long-Term Stability of Perovskite Solar Cells(2), G8567428673
OpenAlex ID: W4409094484