Effects of Chain Orientation in Self-Organized Buffer Layers Based on Poly(3-alkylthiophene)s for Organic Photovoltaics

Wang, Fanji; Hashimoto, Kazuhito; Segawa, Hiroshi; Tajima, Kazuo

doi:10.1021/acsami.7b19174

Cited by 17 publications

(10 citation statements)

References 45 publications

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“…The bottom parts of the films could be edge-on-oriented because of the preferred interaction of the alkyl chains with the substrates and appeared as the small diffraction peak from the lamellar structure in the out-of-plane direction. This behavior of the ( S )-P3MBT-F 17 SSM is similar to that of the SSM system based on poly(3-butylthiophene) that we have reported previously. − , …”

Section: Resultssupporting

confidence: 88%

“…This behavior of the (S)-P3MBT-F 17 SSM is similar to that of the SSM system based on poly(3butylthiophene) that we have reported previously. [20][21][22]24 The CD spectra were measured to investigate the chiral packing structure of the main chains in the (S)-P3MBT, (S)-P3MBT-F 17 , and (S)-P3MBT-F 17 /(S)-P3MBT films (Figure 5a). The CD signal for the (S)-P3MBT film changed from positive to negative as the wavelength increased, which is consistent with the previous work on (S)-P3MBT films.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…For a better understanding of the chiroptical properties in thin films, the material systems with the precise controllability of the film structures such as the orientations and aggregations are highly desired. We have developed semiconducting polymers bearing functional groups with low surface energy, such as fluoroalkyl or oligo(dimethyl siloxane) chains, which form surface-segregated monolayers (SSMs) on the surface of organic semiconductor films. − The orientation of the polymers in SSMs as edge-on (parallel to the surface) or end-on (vertical to the surface) was controlled by careful molecular design. The edge-on-oriented polymers in the SSM had little effect on the properties of the polymer chains inside the films, − whereas the end-on-oriented polymers had a large effect on the chain orientations, crystalline structure, and film morphology in the bulk of the films through the induction effect from the surface layer. − Based on these results, we decided to introduce a chiral moiety into the polymers for end-on-oriented SSMs to investigate the effects of the SSMs on the packing structures of the chiral polymers inside the films.…”

Section: Introductionmentioning

confidence: 99%

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Inversion of Circular Dichroism Signals in Chiral Polythiophene Films Induced by End-On-Oriented Surface-Segregated Monolayers

Wang

Nakano

Segawa

et al. 2021

ACS Appl. Mater. Interfaces

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A chiral polythiophene surfactant based on poly(3-(S)-2-methylbutylthiophene) ((S)-P3MBT) with a semifluoroalkyl group at one end of the main chain was synthesized and used to form surface-segregated monolayers (SSMs). Films of pure (S)-P3MBT mainly adopted the edge-on orientation, whereas (S)-P3MBT films with a SSM of the polymer surfactant (S)-P3MBT-F17 contained a large proportion of end-on-oriented polythiophene, both at the surface and inside the films. The thin films with the SSM showed circular dichroism signals, with the sign opposite to those observed in (S)-P3MBT films. These findings suggest that the orientation-controlled SSM layers induced changes in the packing of the polymer aggregates in the films, resulting in a dramatic change in the excitonic interactions of the chiral semiconducting polymers.

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Section: Resultssupporting

confidence: 88%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inversion of Circular Dichroism Signals in Chiral Polythiophene Films Induced by End-On-Oriented Surface-Segregated Monolayers

Wang

Nakano

Segawa

et al. 2021

ACS Appl. Mater. Interfaces

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“…The self‐organization method not only simplifies the fabrication procedure significantly but also makes the tolerance of the interlayer to thickness variation no need consideration. And hence, intensive investigations have been focused on the self‐organization method in fullerene‐based OSCs …”

Section: Device Characteristics Using Pvp As Cil With Different Procementioning

confidence: 99%

A Self‐Organized Poly(vinylpyrrolidone)‐Based Cathode Interlayer in Inverted Fullerene‐Free Organic Solar Cells

Yang

Zhang

et al. 2018

Advanced Materials

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surface of the film, forming the interlayer and active layer simultaneously. In order to better distinguish, the two approaches are recognized as the step-by-step preparation method and the self-organization method, respectively, in this work. The self-organization method not only simplifies the fabrication procedure significantly but also makes the tolerance of the interlayer to thickness variation no need consideration. And hence, intensive investigations have been focused on the self-organization method in fullerene-based OSCs. [4][5][6][7][8][9][10][11][12] The self-organization method is based on the self-assembly of the interlayer material during the film deposition process, and many factors have been suggested to explain the origin of the migration of the interlayer materials. It has been demonstrated that when an interlayer material has higher surface energy and stronger interaction with the indium tin oxide (ITO) electrode, it may tend to migrate to the near ITO side, and vice versa. [12][13][14][15][16] For instance, Wei et al. introduced fluorocarbon chains to [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) to decrease the surface energy of PC 61 BM, and as a result, the fluorinated PC 61 BM segregated to the top of the AL, forming the CIL and AL simultaneously. [15] By contrast, when PC 61 BM was substituted with high-surfaceenergy moieties, such as amino groups, the modified PC 61 BM could migrate to the interface between the AL and the ITO substrate. [5] Interestingly, poly(ethylene glycol) (PEG) and its derivatives, materials with high surface energies, have been demonstrated to prefer to self-organize at the top of the AL because of the strong interaction between the PEG segment and the top metal electrode. [12,[16][17][18][19][20] Poly(vinylpyrrolidone) (PVP), poly(2-vinylpyridine) (P2VP), poly [(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), polyethyleneimine (PEI), oleamide, and fluorinated zinc oxide have also been used to self-organize CILs in OSCs. [9,13,[21][22][23][24] All the aforementioned materials were applied in fullerene-based OSCs via the self-organization method, and the reported utilization of PVP through self-organization method is associated with a conventional device architecture, [21] which makes its application in the inverted devices seem impossible. Meanwhile, for fullerene-free OSCs, that have more potential for realizing higher photovoltaic performances and in future practical applications, no example has been developed to date.In this work, we demonstrate the first example that uses PVP as the CIL in the inverted OSCs via the self-organization method.Herein, poly(vinylpyrrolidone) (PVP) is used as the cathode interlayer (CIL) through the self-organization method in inverted organic solar cells (OSCs). By coating a solution of PVP and active layer materials onto a glass/indium tin oxide (ITO) substrate, the PVP can segregate to the near ITO side due to its high surface energy and strong intermolecular interaction with the I...

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“…During solution casting processes of organic semiconducting materials into the films, the molecules with the lower surface energy than the other components in the solution can spontaneously segregate onto the film surface to form a monolayer driven by the total energy minimization. This surface segregated monolayer (SSM) is a useful approach to modify the surface properties of the organic semiconducting films [1,2], and to alter the organic interfaces of donor/acceptor (D/A) in planar heterojunction (PHJ) organic photovoltaics (OPVs) [3][4][5] and the organic/metal interfaces in bulk heterojunction (BHJ) OPVs [6][7][8]. In addition, polymer-based SSM molecules showed strong preference of the molecular orientations in the surface layers depending on the substituent positions of the functionality with the low surface energy [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Poly(3-butylthiophene) with Trisiloxane End Group and Its Surface Segregation Behavior in Thin Films

Wang

Hashimoto

Segawa

et al. 2018

J. Photopol. Sci. Technol.

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A poly(3-butylthiophene) derivative with an end group of 1,1,1,3,3,5,5-heptamethyl trisiloxane group (P3BT-Si) was synthesized for the application of surface segregated monolayer (SSM) in polymer films. The surface segregation behaviors, thermal properties and chain orientation of P3BT-Si were investigated. The formation of the surface layer of P3BT-Si was confirmed in the blend films with polystyrene. In contrast to the fluoroalkylterminated polymer (P3BT-F17) that shows strong end-on orientation in the SSM with high crystallinity, P3BT-Si showed edge-on orientation in the SSM with low crystallinity. The difference can be attributed to the more flexible structure of trisiloxane group than the fluoroalkyl chain.

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Effects of Chain Orientation in Self-Organized Buffer Layers Based on Poly(3-alkylthiophene)s for Organic Photovoltaics

Cited by 17 publications

References 45 publications

Inversion of Circular Dichroism Signals in Chiral Polythiophene Films Induced by End-On-Oriented Surface-Segregated Monolayers

Inversion of Circular Dichroism Signals in Chiral Polythiophene Films Induced by End-On-Oriented Surface-Segregated Monolayers

A Self‐Organized Poly(vinylpyrrolidone)‐Based Cathode Interlayer in Inverted Fullerene‐Free Organic Solar Cells

Synthesis of Poly(3-butylthiophene) with Trisiloxane End Group and Its Surface Segregation Behavior in Thin Films

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