In the first period of our adventure in the field of polymer solar cells (2006-2016), we systematically investigated the molecular structure of conjugated polymers for solar cells, including (a) backbone, (b) side chains, and (c) substituents. Our goal was to derive structure-property relationships for conjugated polymers used in bulk heterojunction solar cells, which would facilitate the further design and synthesis of novel conjugated polymers to achieve even higher efficiencies. This systematic approach has paid off significantly; we discovered many useful design principles and applied them to create many novel conjugated polymers that showed exceptionally high device efficiencies at the time.

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In the second period (2016-present), we have been exploring a diverse range of topics concerning polymer solar cells. First, the rapid development of non-fullerene acceptors (NFAs) has pushed the record high efficiency to over 16%, yet there are still many fundamental questions concerning the design rationale for these NFAs, and related device physics (e.g., minimizing loss in the open circuit voltage). Second, a quantitative relationship between the parameters that describe the morphology of the bulk heterojunction and the molecular/polymeric structures of the materials in the BHJ blend is still at large, though significant progress has been made. 

 

Third, to eventually make polymer solar cells a commercial success, one must address the scalability and stability issues of current polymer solar cells. Finally, lowering the cost of polymer solar cells (including cost for materials and processing) and adopting environmentally friendly manufacturing processes also need to be further investigated.

 

Below are selected publications from our efforts in this area.

 

General Reviews:

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• Macromolecules 2012, 45, 607-632

  • https://doi.org/10.1021/ma201648t

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• Macromol. Rapid Commun. 2012, 33, 1162-1177

  • https://doi.org/10.1002/marc.201200129

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• Adv. Mater. 2017, 29, 1601391

  • https://doi.org/10.1002/adma.201601391

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Ternary Blends:

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• J. Am. Chem. Soc. 2012, 134, 5432-5435

  • https://doi.org/10.1021/ja211597w

 

• J. Phys. Chem. Lett. 2013, 4, 1802-1810 (a review)

  • https://doi.org/10.1021/jz400723u

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• Nature Photonics 2015, 9, 491-500 (a review)

  • https://www.nature.com/articles/nphoton.2015.128

 

Fluorine Impact:

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• J. Am. Chem. Soc. 2011, 133 (12), 4625-4631

  • https://doi.org/10.1021/ja1112595

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• Angew. Chem. Int. Ed. 2011, 50 (13), 2995-2998

  • https://doi.org/10.1002/anie.201005451

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• J. Am. Chem. Soc. 2013, 135, 1806-1815

  • https://doi.org/10.1021/ja309289u

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• J. Am. Chem. Soc., 2014, 136, 15566–15576

  • https://doi.org/10.1021/ja5067724

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• Acc. Chem. Res. 2017, 50, 2401−2409 (a review)

  • https://doi.org/10.1021/acs.accounts.7b00326

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• Macromolecules, 2019, 52, 6523-6532

  • https://doi.org/10.1021/acs.macromol.9b01168

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Influence of Molecular Orientation and Molecular Weight:

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• Nature Photonics 2014, 8, 385-391

  • https://www.nature.com/articles/nphoton.2014.55

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• Adv. Mater. 2014, 26, 4456–4462

  • https://doi.org/10.1002/adma.201305251

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Non-Fullerene Acceptors:

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• Adv. Mater. 2017, 29, 1700144.

  • https://doi.org/10.1002/adma.201700144

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• Adv. Mater. 2018, 30, 1706363

  • https://doi.org/10.1002/adma.201706363

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• Adv. Mater. 2018, 30, 1705485

  • https://doi.org/10.1002/adma.201705485

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• Mater. Chem. Front., 2019, 3, 1642  

  • https://doi.org/10.1039/C9QM00314B

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• Nano Research 2019, 12, 2400-2405

  • https://doi.org/10.1007/s12274-019-2362-3