Non-fullerene acceptors with hetero-dihalogenated terminals induce significant difference in single crystallography and enable binary organic solar cells with 17.5% efficiency

Wang, Jinliang; Wang, Lai; An, Qiaoshi; Lü, Yan; Bai, Hairui; Jiang, Mengyun; Mahmood, Asif; Yang, Can; Zhi, Hong‐Fu

doi:10.1039/d1ee01832a

Cited by 136 publications

(96 citation statements)

References 93 publications

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“…[42][43][44][45] Dicyanomethylene-3-ethylrhodanine (RDN) and 3-(dicyanomethylidene)-indan-1-one (IC) are chosen as end functional groups because of their strong electron-withdrawing ability. [46][47][48][49] Particularly, thiophene-fused IC (ThIC) not only has a strong electron-withdrawing ability but could also provide better intermolecular interactions because of its potentially heteroatomic non-covalent interactions. [50][51][52] After Knoevenagel condensation reaction between TDPP-2CHO [53] and RDN, IC, or ThIC, respectively, three DPP-based small molecules were obtained with the high yield of 76% for TDPP-RDN, 79% for TDPP-IC, and 81% for TDPP-ThIC.…”

Section: Synthesis and Structure Characterizationmentioning

confidence: 99%

Unveiling the Interplay among End Group, Molecular Packing, Doping Level, and Charge Transport in N‐Doped Small‐Molecule Organic Semiconductors

Wang

et al. 2021

Adv Funct Materials

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Doped small molecules with high electrical conductivity are desired because they typically show a larger Seebeck coefficient and lower thermal conductivity than their polymer counterparts. However, compared with conjugated polymers, only a few small molecules can show high electrical conductivities. In this study, three n-type small-molecule organic semiconductors with different end functional groups are synthesized to explore the reasons for the low electrical conductivity issue in n-doped small-molecule semiconductors. Charge carrier mobility and doping level are usually considered as two major parameters for achieving high electrical conductivity. TDPP-ThIC with high electron mobility of 0.77 cm 2 V −1 s −1 and high electron affinity, which can be easily n-doped; however, it only displays an electrical conductivity ≈10 −3 S cm −1 . To explore the reasons, the single crystal structure of TDPP-ThIC and the grazing incidence wide-angle X-ray scattering of its n-doped films are carefully analyzed. TDPP-ThIC with a 1D column packing is disclosed and easily distorted by the enthetic n-dopants, which damages the charge transport pathways, and thereby results in low electrical conductivity. The results suggests that only high intrinsic charge carrier mobility and high doping level cannot guarantee high electrical conductivity, and keeping good charge transport pathways after doping is also critical.

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Section: Synthesis and Structure Characterizationmentioning

confidence: 99%

Unveiling the Interplay among End Group, Molecular Packing, Doping Level, and Charge Transport in N‐Doped Small‐Molecule Organic Semiconductors

Wang

et al. 2021

Adv Funct Materials

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“…The chemistry of materials affects their performance. [33][34][35][36] Molecular descriptors represent their structural and chemical features. The molecular descriptors showed high correlation with PCE, as shown in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Learning from Fullerenes and Predicting for Y6: Machine Learning and High‐Throughput Screening of Small Molecule Donors for Organic Solar Cells

et al. 2022

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In recent years, research on the development of organic solar cells has increased significantly. For the last few years, machine learning (ML) has been gaining the attention of the scientific community working on organic solar cells. Herein, ML is used to screen small molecule donors for organic solar cells. ML models are fed by molecular descriptors. Various ML models are employed. The predictive capability of a support vector machine is found to be higher (Pearson's coefficient = 0.75). The best small donors with fullerene acceptors are selected to pair with Y6. New small molecule donors are also designed taking into account quantum chemistry principles, using building units that are searched through similarity analysis. Their energy levels and power conversion efficiencies (PCEs) are predicted. Efficient small molecule donors with PCE > 13% are selected. This design and discovery pipeline provides an easy and fast way to select potential candidates for experimental work.

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“…Hence, many end‐group engineering strategies, including extending π‐conjugation and/or introducing electron‐rich/deficient groups (such as halogenation), have been reported. [ 28–32 ] Among different types of halogenations, fluorination is one of the most important molecular design strategies to further improve the performance of PSCs. [ 33–41 ] First, due to the strong electron‐withdrawing effect with a very small size, the introduction of fluorine atom is beneficial to simultaneously downshift the frontier molecular orbitals and to reduce the optical bandgap without using a large π‐conjugated system.…”

Section: Introductionmentioning

confidence: 99%

“…reported. [28][29][30][31][32] Among different types of halogenations, fluorination is one of the most important molecular design strategies to further improve the performance of PSCs. [33][34][35][36][37][38][39][40][41] First, due to the strong electron-withdrawing effect with a very small size, the introduction of fluorine atom is beneficial to simultaneously downshift the frontier molecular orbitals and to reduce the optical bandgap without using a large π-conjugated system.…”

Section: Introductionmentioning

confidence: 99%

M‐Series Nonfullerene Acceptors with Varied Fluorinated End Groups: Crystal Structure, Intermolecular Interaction, Charge Transport, and Photovoltaic Performance

Zhang

Liao

et al. 2022

Solar RRL

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Intermolecular interaction of nonfullerene acceptors (NFAs) is essential for controlling their photovoltaic performance. Fluorinated substituents attached at the end groups of NFAs can significantly affect their frontier molecular orbitals and intermolecular interactions. Herein, four heteroheptacene‐based NFAs (ML‐1F, ML‐2FO, ML‐2FM, and ML‐2FP) with different fluorinated end groups are designed, synthesized, and characterized. The impact of the end group on the crystal structures, optical, electrochemical, charge transport, and photovoltaic properties of these NFAs are systematically studied. In comparison with the acceptor with monofluorinated end groups, the acceptors with difluorinated end groups show reduced bandgaps and downshifted energy levels. Single‐crystal results demonstrate that the intermolecular interactions including the π–π stacking distance and molecular aggregation behavior of these acceptors are also affected by the variation of end groups thereby leading to the acceptors with varied charge transport properties. In combination with the polymer donor of PM6, ML‐2FM exhibits the highest power conversion efficiency (PCE) of 15.33% with a short‐circuit current density of 23.73 mA cm−2 and a fill factor of 0.734. However, ML‐2FP displays an inferior PCE of 10.48% which is lower than that of ML‐1F (11.41% PCE). The results show that the fluorine substituent number and position of end group are of vital importance in determining their photovoltaic performance.

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Non-fullerene acceptors with hetero-dihalogenated terminals induce significant difference in single crystallography and enable binary organic solar cells with 17.5% efficiency

Abstract: Despite dihalogenation of terminals is an effective strategy to achieve efficient nonfullerene acceptors (NFAs)-based organic solar cells (OSCs), hetero-dihalogenated terminals are quite difficult to obtain. Here, we firstly synthesized two...

Cited by 136 publications

References 93 publications

Unveiling the Interplay among End Group, Molecular Packing, Doping Level, and Charge Transport in N‐Doped Small‐Molecule Organic Semiconductors

Unveiling the Interplay among End Group, Molecular Packing, Doping Level, and Charge Transport in N‐Doped Small‐Molecule Organic Semiconductors

Learning from Fullerenes and Predicting for Y6: Machine Learning and High‐Throughput Screening of Small Molecule Donors for Organic Solar Cells

M‐Series Nonfullerene Acceptors with Varied Fluorinated End Groups: Crystal Structure, Intermolecular Interaction, Charge Transport, and Photovoltaic Performance

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