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Abstract Until recently, solution‐processable organic photovoltaics (OPVs) mainly relied on fullerene derivatives as then‐type material, paired with ap‐type conjugated polymer. However, fullerene derivatives have disadvantages that limit OPV performance, thus fueling research of non‐fullerene acceptors (NFAs). Initially, NFAs showed poor performance due to difficulties in obtaining favorable blend morphologies. One example is our work with 2,6‐dialkylamino core‐substituted naphthalene diimides. Researchers then learned to control blend morphology by NFA molecular design. To limit miscibility with polymer while preventing excessive self‐aggregation, non‐planar, twisted or 3D structures were reported. An example of a 3D structure is our work with homoleptic zinc(II) complexes of azadipyrromethene. The most recent design is a planar A‐D‐A conjugated system where the D unit is rigid and has orthogonal side chains to control aggregation. These have propelled power conversion efficiencies (PCEs) to ∼14 %, surpassing fullerene‐based OPVs. These exciting new developments prompt further investigations of NFAs and provide a bright future for OPVs.
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A zinc( ii ) complex of di(naphthylethynyl)azadipyrromethene with low synthetic complexity leads to OPV with high industrial accessibility
Organic photovoltaics have reached high power conversion efficiencies (PCE) using non-fullerene acceptors (NFAs). However, the best NFAs tend to have complex syntheses, limiting scalability. Among polymer donors, regioregular poly(3-hexylthiophene) (P3HT) has the greatest potential for commercialization due to its simple synthesis and good stability, but PCEs have been limited. It is thus imperative to find scalable NFAs that give high PCE with P3HT. We report a zinc( ii ) complex of di(naphthylethynyl)azadipyrromethene (Zn(L2) 2 ) as a non-planar NFA that can be synthesized on the gram scale using inexpensive starting materials without chromatography column purification. The NFA has strong absorption in the 600–800 nm region. Time-dependent density-functional theory calculations suggest that the low-energy absorptions can be understood within a four-orbital model involving transitions between π-orbitals on the azadipyrromethene core. OPVs fabricated from P3HT:Zn(L2) 2 blends reached a PCE of 5.5%, and the PCE was not very sensitive to the P3HT:Zn(L2) 2 weight ratio. Due to its shape, Zn(L2) 2 shows isotropic charge transport and its potential as an electron donor is also demonstrated. The combination of simple synthesis, good PCE and photostability, and tolerance to the active material weight ratio demonstrates the potential of Zn(L2) 2 as an active layer material in OPVs.
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- Award ID(s):
- 1904868
- PAR ID:
- 10164200
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 7
- Issue:
- 42
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 24614 to 24625
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9ta08654d
