Insights into constitutional isomeric effects on donor–acceptor intermolecular arrangements in non-fullerene organic solar cells

Lee, Jung-Ho; Go, Eun Min; Dharmapurikar, Satej S.; Xu, Junqing; Lee, Sang Myeon; Jeong, Mingyu; Lee, Kyu Cheol; Oh, Jiyeon; Cho, Yongjoon; Zhang, Chunfeng; Kwak, Sang Kyu; Yang, Changduk

doi:10.1039/c9ta07133d

Cited by 40 publications

(35 citation statements)

References 71 publications

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“…CG-MD simulations of the morphological characteristics of high-efficiency polymer:NF-SMA systems have started to emerge. Lee and colleagues have studied the morphology of PBDB-T:F-ITIC blends using the Martini force field [77]; they compared the o-F-ITIC and m-F-ITIC isomers and highlighted several morphological distinctions. Although the difference between the two acceptors is just the location of the fluorine atoms on the side chain (ortho versus meta positions), the PBDB-T:o-F-ITIC blend presents a larger interfacial area and more extended PBDB-T chains.…”

Section: From Local To Global Morphologymentioning

confidence: 99%

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Wang

Kupgan

Brédas

2020

Trends in Chemistry

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Substantial enhancements in the efficiencies of bulk-heterojunction (BHJ) organic solar cells (OSCs) have come from largely trial-and-error-based optimizations of the morphology of the active layers. Further improvements, however, require a detailed understanding of the relationships among chemical structure, morphology, electronic properties, and device performance. On the experimental side, characterization of the local (i.e., nanoscale) morphology remains challenging, which has called for the development of robust computational methodologies that can reliably address those aspects. In this review, we describe how a methodology that combines all-atom molecular dynamics (AA-MD) simulations with density functional theory (DFT) calculations allows the establishment of chemical structure-local morphology-electronic properties relationships. We also provide a brief overview of coarse-graining methods in an effort to bridge local to global (i.e., mesoscale to microscale) morphology. Finally, we give a few examples of machine learning (ML) applications that can assist in the discovery of these relationships. Active-Layer Morphology Impacts Device PerformanceSince the BHJ architecture was introduced in the mid-1990s [1,2], OSCs have witnessed substantial improvements in their power conversion efficiencies (PCEs). The active layer of a BHJ OSC is formed by a blend of an electron-donor and an electron-acceptor material, with the two components mixing down to the~10 nm scale; Figure 1A illustrates a typical polymer: fullerene BHJ architecture with the basic electronic processes described in the legend [3] (the chemical structures of the donor and acceptor materials mentioned in this review are provided in Figures 1B and 3A). In conjunction with molecular design, efforts to optimize the active-layer morphology have led to record PCEs of 11.0%, 11.7%, and 18.2% for all-polymer, polymer:fullerene, and polymer:non-fullerene small-molecule acceptor (NF-SMA) single-junction BHJ OSCs, respectively [4][5][6][7][8]. A key element of recent, impressive PCE enhancements has come from switching from fullerenes to NF-SMAs as electron-acceptor materials. Efficient NF-SMAs began with the synthesis of ITIC by Zhan and coworkers in 2015 and currently mainly revolve around the Y6 acceptor reported by Zhou and coworkers [9,10].One of the positive characteristics of efficient polymer:NF-SMA OSCs is their reduced nonradiative voltage losses [6,11,12], which comes at least partly from the molecular design of pairs of polymer donors and NF-SMAs where the energetic offset between either the ionization energies or the electron affinities of the donor and acceptor components is minimized [12]. When the donor and acceptor components possess appropriate energy levels and optical absorption profiles, a meta-analysis by Jackson and colleagues on some 150 BHJ OSCs has suggested that the PCEs are then morphology limited [13]. Thus, a critical task is to be able to

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Section: From Local To Global Morphologymentioning

confidence: 99%

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Wang

Kupgan

Brédas

2020

Trends in Chemistry

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“…Halogenation at the core unit or at the end group of the NF‐SMAs with different number of halogen atoms or in different substituted position/aromatic groups is a significantly effective strategy to modulate molecular energy levels and absorption range and improve the blend morphology and device performance. [ 66–80 ] Compared with the popular fluorinated or chlorinated IC functionalized NF‐SMAs, although brominated NF‐SMAs show lower synthesis cost and are much easier for postmodification, the brominated IC has been less incorporated into NF‐SMAs. [ 14,69,70,79,80 ] Until recently, Prof. Li's and Prof. Chen's groups independently reported the monobrominated IC functionalized NF‐SMAs with different core unit, which both exhibited slightly higher PCE in comparison with corresponding monofluorinated IC functionalized NF‐SMAs.…”

Section: Introductionmentioning

confidence: 99%

Tetrabromination versus Tetrachlorination: A Molecular Terminal Engineering of Nonfluorinated Acceptors to Control Aggregation for Highly Efficient Polymer Solar Cells with Increased V_oc and Higher J_sc Simultaneously

et al. 2020

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Polymer solar cells (PSCs) have achieved a huge breakthrough in the past 5 years with the combinational contributions from the developments of nonfullerene acceptors (NFAs), polymeric donors, and kind of redundant of device engineering. [1-12] Compared with traditional fullerene acceptors, AD A framework nonfullerene small molecular acceptors (NF-SMAs) have significant advantages in broader absorption range, tunable molecular structure and energy levels, and diversified donor materials for matching. [13-23] Therefore, many such typed NF-SMAs have been synthesized and become the mainstream materials for the development of high-efficiency PSCs. [24-36] Recently, the power conversion efficiencies (PCEs) of NF-SMAs-based PSCs have been sharply increased over 16% in single-junction binary and ternary devices, indicating their great potentials for further practical application. [37-57] NF-SMAs, such as ITIC and Y6, typically comprise an electron-rich fused core, side chain group, and electron-deficient terminal groups, and all of which can be modified by introducing functional groups or atoms to better understand the structureproperty relationship and improve the device performance of ITIC or Y6 series-based PSCs. [58,59] Molecular engineering on ending groups of NF-SMAs, typically, is the last synthetic step in the synthesis of NF-SMAs and mainly contributed to the intermolecular packing, which played a vital role in optimizing the electronic and morphological properties as well as in enhancing charge transport and device performance. [60-65] Halogenation at the core unit or at the end group of the NF-SMAs with different number of halogen atoms or in different substituted position/aromatic groups is a significantly effective strategy to modulate molecular energy levels and absorption range and improve the blend morphology and device performance. [66-80] Compared with the popular fluorinated or chlorinated IC functionalized NF-SMAs, although brominated NF-SMAs show lower synthesis cost and are much easier for

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“…Many reported high‐performance FREAs used 1FIC or 2FIC as end groups (e.g., ITIC‐Th1, [ 12 ] FOIC, [ 14 ] IT‐4F, [ 35 ] and Y6 [ 36 ] ), and the PCEs of OSCs based on fluorinated FREAs reached 17–18%. [ 37,38 ] A few works studied the effects of fluorination on end groups [ 8,39,40 ] or side chains [ 41 ] separately, but a comparison of end‐group and side‐chain fluorinations has not been reported.…”

Section: Introductionmentioning

confidence: 99%

Effects of Fluorination Position on Fused‐Ring Electron Acceptors

et al. 2020

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Insights into constitutional isomeric effects on donor–acceptor intermolecular arrangements in non-fullerene organic solar cells

Abstract: The novel constitutional isomeric acceptors (o-F-ITIC and m-F-ITIC) are developed and they show the huge disparity of intermolecular interactions and/or arrangements with the donor polymer leading a significant variation in PCE of OSCs.

Cited by 40 publications

References 71 publications

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Tetrabromination versus Tetrachlorination: A Molecular Terminal Engineering of Nonfluorinated Acceptors to Control Aggregation for Highly Efficient Polymer Solar Cells with Increased V_oc and Higher J_sc Simultaneously

Effects of Fluorination Position on Fused‐Ring Electron Acceptors

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Insights into constitutional isomeric effects on donor–acceptor intermolecular arrangements in non-fullerene organic solar cells

Abstract: The novel constitutional isomeric acceptors (o-F-ITIC and m-F-ITIC) are developed and they show the huge disparity of intermolecular interactions and/or arrangements with the donor polymer leading a significant variation in PCE of OSCs.

Cited by 40 publications

References 71 publications

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Organic Photovoltaics: Relating Chemical Structure, Local Morphology, and Electronic Properties

Tetrabromination versus Tetrachlorination: A Molecular Terminal Engineering of Nonfluorinated Acceptors to Control Aggregation for Highly Efficient Polymer Solar Cells with Increased Voc and Higher Jsc Simultaneously

Effects of Fluorination Position on Fused‐Ring Electron Acceptors

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Tetrabromination versus Tetrachlorination: A Molecular Terminal Engineering of Nonfluorinated Acceptors to Control Aggregation for Highly Efficient Polymer Solar Cells with Increased V_oc and Higher J_sc Simultaneously