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Spiro Linkage as an Alternative Strategy for Promising Nonfullerene Acceptors in Organic Solar Cells
Author(s) -
Wu XiaoFeng,
Fu WeiFei,
Xu Zheng,
Shi Minmin,
Liu Feng,
Chen HongZheng,
Wan JunHua,
Russell Thomas P.
Publication year - 2015
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201502413
Subject(s) - materials science , crystallinity , intermolecular force , organic solar cell , moiety , fluorene , molecule , small molecule , dimer , polymer solar cell , polymer chemistry , energy conversion efficiency , polymer , stereochemistry , organic chemistry , chemistry , optoelectronics , biochemistry , composite material
This work focuses on developing diketopyrrolopyrrole (DPP)‐based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF‐DPP s, have an X‐shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro‐dimer of DPP‐fluorene‐DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2‐ethylhexyl (EH), linear n ‐octyl (C8), and n ‐dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N , N ‐positions of the DPP moiety to tune molecular interactions. SF‐DPPEH , the best candidate in SF‐DPP s family, when blended with poly(3‐hexylthiophene) (P3HT) showed a moderate crystallinity and gives a J sc of 6.96 mA cm −2 , V oc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF‐DPPC8 and SF‐DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced J sc . Coupling DPP units with SF using an acetylene bridge yields SF‐A‐DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors.