Chlorinated Isoindigo-Based Conjugated Polymers: Effect of

Subscriber access provided by University of South Dakota

Article

Chlorinated isoindigo-based conjugated polymers: effect of rotational freedom of conjugated segment on crystallinity and charge-transport characteristics Jong-Jin Park, Yeong-A Kim, Seung-Hoon Lee, Juhwan Kim, Yunseul Kim, Dae-Hee Lim, and Dong-Yu Kim ACS Appl. Polym. Mater., Just Accepted Manuscript • DOI: 10.1021/acsapm.8b00019 • Publication Date (Web): 10 Dec 2018 Downloaded from http://pubs.acs.org on December 18, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Polymer Materials

Chlorinated Isoindigo-based Conjugated Polymers: Effect of Rotational Freedom of Conjugated Segment on Crystallinity and Charge-Transport Characteristics Jong-Jin Park1, Yeong-A Kim2, Seung-Hoon Lee3, Juhwan Kim4, Yunseul Kim1, Dae-Hee Lim1 and Dong-Yu Kim1*

1 Heeger

Center for Advanced Materials, School of Materials Science and Engineering,

Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Kore

2

Basic Materials & chemicals R&D, LG Chem., Yeosu 59611, Republic of Korea

3

Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Republic of

Korea

4

Future Technology Research Center, Corporate R&D, LG Chem Research Park, Seoul

07796, Republic of Korea

1

ACS Paragon Plus Environment

ACS Applied Polymer Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 37

KEYWORDS: chlorinated conjugated polymer, rotational freedom, organic field-effect transistors, crystallinity, Charge-Transport Characteristics

ABSTRACT

The chlorinated isoindigo (CI) is a promising building block for organic semiconducting materials because the favourable properties, such as ready availability, lower price, and higher capability to hold the electron density than fluorine atoms, make them advantageous for use in semiconducting materials. It was reported that CI can be more readily synthesized than fluorinated isoindigo (FI) and CI-based conjugated polymer exhibited comparable device performance with the FI-based conjugated polymer. Chorine substituted conjugated molecules, however, have been less investigated than that of fluorine atom, presumably, due to the large size of chlorine atom, which induces steric hindrance effects in the 2


Page 3 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conjugated backbone. In this study, we systematically investigate the effect of the structural property – flexibility vs rigidity – of the donor unit on the crystallinity and charge transport characteristics of chlorinated isoindigo acceptor-based D-A type conjugated polymers to understanding the structure-property relationships of chlorinated isoindigo based conjugated polymers. Interestingly, in an X-ray diffraction analysis, although TV unit is more planar structure than BT unit, PCIBT film exhibited much stronger peak intensity and highly extended lamellar peak up to (400) compared to PCITV film after the thermal annealing process. This indicated that PCIBT had more improved molecular ordering and crystalline structure than PCITV. This may be associated with the BT unit having higher rotational freedom compared to that of the TV unit. This property of the BT unit can facilitate thermalassisted polymer chain packing in film state that results in an enhanced molecular ordering of PCIBT after thermal annealing process. Therefore, PCIBT exhibited higher electron mobility (1.7 cm2V-1s-1) than PCITV (0.39 cm2v-1s-1) in OFETs due to enhanced intermolecular charge transport between polymer chains.

INTRODUCTION Conjugated polymeric semiconductors used in organic field-effect transistors (OFETs) 3



Page 4 of 37

have attracted tremendous scientific interest due to their tunable electronic properties, cost effective manufacturing processes, large-area fabrication, and potential use in flexible devices.1–5 Among these, the electron donor-electron acceptor (D-A) type conjugated polymeric semiconductors have been extensively investigated by many research groups because they can facilitate the efficient intermolecular charge carrier hopping through strong intermolecular interactions with neighbouring polymer chains in tight π-π stacking molecular structures.6,7 As a result of these efforts, it has been reported that high hole-mobility of over 10 cm2 V-1 s-1 has been achieved by diketopyrrolopyrrole8 and thienoisoindigo9-based D-A type conjugated polymeric semiconductors. Such hole-mobility values exceed those of amorphous silicon-based field-effect transistors (FETs).10 Compared to that of p-type conjugated polymeric semiconductors, however, the development of n-type conjugated polymeric semiconductors still lags far behind.11,12 This is mainly due to the lack of strong electron-deficient units for designing n-type conjugated polymeric semiconductors with deep lowest unoccupied molecular orbital (LUMO) energy levels for facile electron injection and efficient transport.7,13 High performance n-type conjugated polymeric semiconductors are required for realising practical organic electronic 4


Page 5 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


devices, such as complementary metal-oxide-semiconductor (CMOS)-like logic circuits14, organic thermoelectronics15, and all-polymer solar cells16. Thus, a more concerted effort is needed for enhancing the n-type performance through molecular design and synthesis. One useful molecular design method for improving n-type performance of conjugated polymeric semiconductors is replacing the hydrogen atoms in aromatic and heterocyclic cores with electron-withdrawing groups (EWGs), such as halogens, cyano (nitrile), and diimide moieties.17 The LUMO energy level of the conjugated polymers can be effectively lowered by EWGs, which can pull out the electrons from the π-conjugated backbone due to their strong electronegativity.18 Thus, various n-type polymeric semiconductors have been reported by introducing fluorine atom19,20 and cyano (nitrile) moieties21. Especially, introducing fluorine atom into the conjugated molecules is a popular approach for material modification because the small size of fluorine atom can effectively modulate the LUMO energy level without harmful steric effects. However, synthesis of fluorinated conjugated molecules suffer from very long synthetic steps and high price. On the other hand, favourable properties of chlorine atoms, such as ready availability, lower price, and higher capability to hold the electron density than fluorine atoms22, make them advantageous for 5



Page 6 of 37

use in semiconducting materials. Pei and co-workers have also reported that chlorinated isoindigo (CI) can be more readily synthesized than fluorinated isoindigo (FI). Furthermore, the CI-based conjugated polymer exhibited comparable device performance with the FIbased conjugated polymer.23 Because of these advantages, research about introducing chlorine atom into the conjugated backbone have been reported24–27, but it is still less investigated than that of fluorine atom, presumably, due to the large size of chlorine atom, which induces steric hindrance effects in the conjugated backbone.22,23 The large steric hindrance in the conjugated backbone might disturb the film crystallinity and chain orientation. However, it is known that when conjugated backbone has the flexible segments, it can help the chain rearrangement during the thermal annealing process due to higher rotational freedom.4,28 Therefore, it is expected that the low film crystallinity and chain orientation of the conjugated polymer induced by large size of chlorine atom can be improved by introducing a flexible segment, which can maximize the thermal annealing effect, into the polymer backbone. Moreover, we can further understand the structureproperty relationship of chlorine substituted conjugated polymer, which can result in contributing to an improvement the n-type performance of OFET. 6


Page 7 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In this study, we systematically investigate the effect of the structural property – flexibility vs rigidity – of the donor unit on the crystallinity and charge transport characteristics of CI acceptor-based D-A type conjugated polymers. The CI consists of two symmetrical heteroaromatic rings, which give rise to strong electron-withdrawing characteristics. This can also generate effective intermolecular interactions through the van der Waals interactions.10,29 As for the donor blocks, 2,2´-bithiophene (BT), was chosen as a relatively flexible segment, and (E)-1,2-di(thiophen-2-yl)ethene (TV) was applied as a rigid segment, and because of their similar sizes, we assume that the electron density of conjugated polymers could be similarly affected.4 Finally, two D-A type conjugated polymers, poly{(E)6-([2,2'-bithiophen]-5-yl)-5,5'-dichloro-1,1'-bis(2-decyltetradecyl)-[3,3'-biindolinylidene]-2,2'dione} (PCIBT), and poly{(E)-5,5'-dichloro-1,1'-bis(2-decyltetradecyl)-6-(5-((E)-2-(thiophen2-yl)vinyl)thiophen-2-yl)-[3,3'-biindolinylidene]-2,2'-dione} (PCITV), which have different rotational freedom of donors, were copolymerized by Stille-cross coupling polymerization. Both polymers showed n-type dominant ambipolar charge carrier characteristics. Interestingly, PCIBT, which has higher rotational freedom, showed higher electron mobility of 1.7 cm2V-1s-1, after thermal annealing, which could be contrary to the common molecular 7



Page 8 of 37

design principle that the rigid structure could be more favourable for achieving high mobility. We believe that more flexible nature of BT unit could effectively amplify thermally assisted chain packing upon thermal annealing process.

RESULTS AND DISCUSSION Scheme 1. Synthetic approaches for PCIBT and PCITV

R N

Br Cl

R N

S

Me3Sn

Pd2(dba)3, P(o-tol)3, toluene 110 oC

O

N R

Br

R= 2-decyltetradecyl

Cl S

Cl

S

n

S

n

N R

O

PCIBT 85 %

Cl O

O

SnMe3

S

Me3Sn

S S

R N

SnMe3

Pd2(dba)3, P(o-tol)3, toluene 110 oC

Cl

O

O

Cl

S

N R

PCITV 94 %

Synthesis and Characterisation. The synthetic approaches of PCIBT and PCITV are outlined in Scheme 1. Each monomer (CI, BT, and TV) was synthesized following the procedures outlined in literature.23,28,30 The polymers PCIBT and PCITV were copolymerized by Stille polymerization using the corresponding donor units (BT or TV) and CI with high yield. The crude polymers were purified by soxhlet extraction with methanol, hexane, methylene chloride, chloroform, and chlorobenzene. The methanol, hexane, methylene chloride, and chloroform were used to remove metal residue and low-molecular-weight oligomers of the crude polymers. The last chlorobenzene fractions were precipitated into 8


Page 9 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


methanol to obtain the purified polymers. The molecular weights of both polymers were evaluated by high temperature gel permeation chromatography (HT-GPC) using polystyrene standards with hot 1, 2, 4-trichlorobenzene as eluent at 150 oC. The results are summarised in table 1. The thermal properties of the two polymers were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry analysis (DSC). They exhibited good thermal stabilities with high thermal decomposition temperatures (Td, 5 % weight loss of polymers) over 400 oC, and they did not display any thermal transition peaks in DSC curves (table 1, figure s1 and figure s2 in the supporting information). Table 1. Summary of physical properties of the polymers. Polymer

[kg

Mn

Mw

mol-1]

mol-1]

[kg

PDI

Td

λmaxsol

λmaxfilm

Egopt.

EHOMO

ELUMO

[℃]

[nm]

[nm]

[eV]

[eV]

[eV]

PCIBT

44

117

2.6

405

637

645

1.59

- 5.54

- 3.63

PCITV

55

125

2.3

408

640

646

1.58

- 5.35

- 3.63

Theoretical Calculations. Density functional theory (DFT) calculations were performed for the Gaussian 09 at B3LYP/6-311G (d, p) level to determine the optimized geometry of dimers of both polymers. The long alkyl side chain in the dimers was replaced with methyl group to simplify the calculations. The optimized geometries and the total inter-ring angles (θ) of the two dimers are displayed in figure 1a and figure 1b. The large steric hindrances 9



Page 10 of 37

were induced by chlorine atoms, as expected, between CI acceptors and each of the donor units of the polymers (θCI-BT: 44.5 ° in PCIBT figure 1a and θCI-TV: 43.1 ° in PCITV figure 1b). This large torsional angle can potentially deteriorate the crystalline packing in the film. However, besides the torsional angle, the crystalline behaviour of conjugated polymers can also be affected by the inter-ring rotation energy barriers of the conjugated backbone.31 Thus, in order to confirm the rotational freedom of each polymer, the rotational energy barriers of the inter-ring bond between each of the sub-units, CI-BT, CI-TV, single bond in BT (T-T), and single bond in TV (T-V) were calculated by changing the dihedral angles at intervals of 15 °.32,33 The rotational energy barrier profiles are displayed in figure 1c. When CI-BT and CI-TV bonds rotate within syn-conformation, the maximum energy barriers at 0 ° are calculated to be 2.45 and 2.29 kcal mol-1, respectively. Since the rotational energy barrier between the CI acceptors and each of the donor units is similar, the final rotational freedom of each of the polymers can be determined by the inter-ring energy barriers inside the donor units. The BT unit has a weakly conjugated single bond (T-T), which can rotate between the thiophenes. Although the TV unit has the two single bond, it exhibits coplanar structure and 10


Page 11 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


show rigid characteristic, because well conjugated vinylene bond between two adjacent thiophenes suppress the bond rotation of single bonds. As shown in figure 1c, when the TT bond rotates within syn-conformation, it has a much lower rotational energy barrier than that of T-V bond. This means that T-T bond has a higher degree of rotational freedom than T-V bond and other bonds (CI-BT and CI-TV). Furthermore, in the Boltzmann population (figure 1d), which can explain the degree of freedom of the each bond at room temperature32, the more steepened potential energy surface of T-V bond was observed than that of T-T bond in syn-conformation regions. This can suggest that T-V bond is more rigid than T-T bond. Therefore, it can be predicted that the rotational freedom of PCIBT may be higher than that of PCITV because PCIBT has single bonds (T-T) that can rotate with lower energy.

11



Page 12 of 37

Figure 1. Optimized geometries of (a) PCIBT and (b) PCITV dimer units with key dihedral angles. (c) Rotation energy profiles of inter-rings: CI-TV(red), CI-BT(blue), T-T(green), and T-V(pink). (d) Boltzmann populations in syn-conformation of inter-rings.

Optical and Electrochemical Properties. The optical properties of conjugated polymers, PCIBT and PCITV, were investigated by ultraviolet-visible (UV-vis) absorption spectroscopy in dilute chloroform, pristine films, and 250 oC annealed films. The maximum absorption wavelength (λmax), the absorption onset wavelength (λonset), and the optical bandgap (Egopt) are summarised in table 1. Dual absorption bands can be observed in the solutions, pristine films, and annealed films in figure 2a and figure 2b. The high-energy absorption band (300500 nm) is assigned to the localised π-π* transition, and the low energy absorption band (500-800) is assigned to the internal charge transfer (ICT) between D-A units.11,34 It is known 12


Page 13 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


that the absorption band and the vibronic peak intensity can be affected by molecular ordering and crystallinity change in polymer film.11,23 Compared to that in the solution state, increased 0-0 vibronic peaks of the two polymers clearly appeared in the film state, which means that enhanced intermolecular interaction between the conjugated backbones is expected in the film state.11 Interestingly, although the TV unit is known to have a more coplanar structure than the BT unit, PCIBT showed more enhanced 0-0 vibronic peak intensity than PCITV. Additionally, the further enhanced 0-0 vibronic peak intensity of the PCIBT thin film appeared after thermal annealing at 250 oC,

but that of the annealed PCITV thin film did not improve. These results indicate that

PCIBT formed more improved molecular ordering in the film after thermal annealing than PCITV. This could be associated with the more flexible nature of the BT unit in PCIBT backbone, which provides the opportunity for more ordered molecular structures to be formed in the film after the thermal annealing process due to its low rotation energy barrier. Cyclic voltammetry (CV) measurement was performed to evaluate the frontier energy levels of conjugated polymers in an acetonitrile solution containing 0.1 M Bu4NPF6 as the supporting electrolyte. The cyclic voltammograms and the electrochemical properties of both 13



Page 14 of 37

polymers are presented in figure 2c and table 1. The HOMO and LUMO energy levels of both polymers were calculated from the onset points of the oxidation curve, reduction curve, and the half-wave potential of the ferrocene using the equations: EHOMO = - (Eox E½(ferrocene) + 4.8 V) and ELUMO = - (Ered - E½(ferrocene) + 4.8 V). The onset oxidation potentials (Eox) of PCIBT and PCITV were measured 1.26 V and 1.07 V, respectively and the onset reduction potentials (Ered) were measured -0.65 V for PCIBT and -0.65 V for PCITV. The half-wave potential E1/2(ferrocene) was calculated to be 0.52 V. Thus, the HOMO energy levels of PCIBT and PCITV were calculated to be -5.54 and -5.35 eV, and the LUMO energy levels were calculated as -3.63 eV and -3.63 eV, respectively. The PCITV had slightly higher HOMO energy levels than PCIBT because the TV unit has more stronger electron donating property than the BT unit.35–37

14


Page 15 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. UV-vis absorption spectra of (a) PCIBT, and (b) PCITV. (c) Reduction and (d) Oxidation cyclic voltammograms of PCIBT, PCITV, and ferrocene.

Figure 3. 2D-GIWAXS patterns of (a) pristine PCIBT film, (b) annealed at 250 ℃ PCIBT film, (c) pristine PCITV 15



Page 16 of 37

film, (d) annealed at 250 ℃ PCITV films, (e) out of plane 1-D profiles, and (f) in plane 1-D profiles.

Thin-Film Crystallinity and Morphology Analysis. Grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) were performed to investigate the thin film crystallinity and the morphology of chlorinated isoindigo-based D-A type conjugated polymers. 2D-GIWAXS patterns and 1-D profile graphs of pristine and annealed films at 250 oC

– which is the optimized annealing condition – are displayed in figure 3. The

crystallographic parameters (lamellar d-spacing and π-π stacking d-spacing) of the polymers are summarised in table 2. The pristine films of PCIBT and PCITV exhibited (100) peaks at 0.232 Å-1 and 0.230 Å-1 in the out-of-plane direction corresponding to lamellar stacking d-spacing of 27.1 Å and 27.2 Å, respectively. Both polymers showed up to second order (200) diffraction peaks, indicating that they form similar lamellar packing in the pristine films. After thermal annealing at 250 ℃, both polymers exhibited extended out-of-plane peaks to a value of the fourth order (400) for PCIBT and third order (300) for PCITV. Although the improved lamellar orientation are observed in both polymers, PCIBT showed much stronger peak intensity and more long-range out-of-plane peaks than PCITV.

16


Page 17 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Moreover, the change of coherence length (Lc), which calculated following the Scherrer equation from full width half-maximum (fwhm) of the (100) diffraction peaks, after the thermal annealing process is more distinct for PCIBT film than PCITV film (ΔLc of PCIBT: 27.5 and ΔLc of PCITV: 20.1). This suggests that the chain conformation change was more actively occurred in the annealed PCIBT film compared to annealed PCITV film. Furthermore, as shown in figure 3f, more distinct in-plane (010) diffraction peaks and shorter π-π stack distances appeared in the annealed PCIBT film (3.7 Å for PCIBT and 3.8 Å for PCITV), indicating that the annealed PCIBT film formed more ordered edge-on orientation than the annealed PCITV film. Table 2. The crystallographic parameters of PCIBT and PCITV. Out of plane Polymer

PCIBT PCITV

d(100)

In plane qxy(010) [Å-

d(010)

1]

[Å]

-

-

-

83.3

4.1

1.702

3.7

0.0773

74.8

-

-

-

0.0609

94.9

6.1

1.655

3.8

Fwhm [Å-1]

Lc [Å]

g [%]

27.1

0.1035

55.8

0.240

26.2

0.0693

n/a

0.230

27.2

250

0.247

25.5

TA [℃]

qz(100) [Å-1]

n/a

0.232

250

[Å]

Additionally, we calculated the paracrystalline distortion parameter (g) to confirm paracrystalline nature of annealed polymer films using out of plane (h00) peaks, and the

17



Page 18 of 37

corresponding δd-h2 curve is displayed in the supporting information figure S4.38,39 The calculated g values of PCIBT and PCITV were obtained to be 4.1% and 6.1%, respectively. The annealed PCIBT films show smaller g value than annealed PCITV film. It means that more ordered crystalline structure was formed in annealed PCIBT films than PCITV film by thermal annealing process. It is considered that inter-ring rotation energy barriers are different in the donor units. Large torsion angles between the donor units and the CI acceptors, caused by the chlorine atoms, disturbed the tight packing of polymer chains, orientation, and crystallinity in the pristine films of both polymers regardless of the donor units. However, the better flexible nature of the BT unit in the PCIBT has low inter-ring rotation energy barriers in the conjugated backbone, which leads to the amplification of the thermal-assisted chain packing. The PCITV, on the other hand, contains the intrinsically rigid TV units, which means that it is less influenced by the thermal annealing process. Therefore, annealed PCIBT film show more ordered orientation and crystalline structure than annealed PCITV film. These results also correlated well with the UV-vis absorption analysis.

18


Page 19 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. AFM height images of (a) pristine PCIBT, (b) annealed at 250 ℃ PCIBT, (c) pristine PCITV, and (d) annealed at 250 ℃ PCITV films.

The same tendency is observed in the AFM morphology analysis. Figure 4 displays the height images of both polymers, which show nano-fibril morphologies. Both polymers exhibit similar root-mean-square roughness (Rrms) in pristine films. After thermal annealing, the Rrms value of PCIBT clearly increase from 0.72 nm to 1.1 nm but, that of PCIBT only increase slightly from 0.72 nm to 0.89 nm. Furthermore, annealed PCIBT film shows larger grain and clearer fibrillarstructure than annealed PCITV film. These results indicating that PCIBT film has a stronger tendency to aggregate11 during the thermal annealing process than PCITV film. The large grain size can reduce the grain boundaries, thus minimize the charge-hopping barriers between the grains.40 The results of the GIWAXS and AFM analyses demonstrate that PCIBT has a higher degree of crystalline tendency during thermal annealing process, which arises from low inter-ring rotational energy barriers. This could be favourable to better intermolecular interactions 19



Page 20 of 37

between the chains, and in consequence, facilitate improved intermolecular charge carrier transport.

Figure 5. Transfer (a, b, e, and f) and output (c, d, g, and h) characteristics of (a-d) PCIBT and (e-h) PCITV.

Charge-Transport Properties. To investigate the charge-transport properties of the CI acceptor-based D-A type conjugated polymer, top-gate/bottom-contact (TG/BC) OFET devices were fabricated. The polymer solutions (3 mg/mL in trichloroethylene) were spincoated on the patterned Au/Ni substrates as the semiconducting layer. After the thermal annealing process, a PMMA solution was spin-coated onto the semiconducting layer as the dielectric layer, and then the aluminium layer was thermally evaporated as the electrode

20


Page 21 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


layer. The specific fabrication methods are provided in the experimental section. The transfer and output curves of the OFET devices are displayed in figure 5. The field-effect mobility (μFET) of the conjugated polymers were calculated from the saturation regimes. The key parameters of the OFET devices – μFET, threshold voltage (Vth), and on/off current ratio – are reported in table 3. Although non-halogenated isoindigo based conjugated polymers tend to show holetransport characteristic41–43, both CI based conjugated polymer (PCIBT and PCITV) exhibited n-channel dominant ambipolar characteristics because chlorine atoms have electron-withdrawing properties that can lower the LUMO energy levels of polymers, which, in turn, reduces the energy barrier for the injecting electrons. In pristine film, the average hole mobility (μh) of PCIBT and PCITV were calculated as 0.06 and 0.07 cm2 V-1s-1, and the electron mobility (μe) were calculated as 0.12 and 0.08 cm2 V-1s-1, respectively. Both polymers showed similar mobility in the pristine film because they form similar lamellar packing. Under optimized annealed film conditions, PCIBT and PCITV exhibit 0.25 and 0.08 cm2 V-1s-1 for μh, and 1.23 and 0.28 cm2 V-1s-1 for μe, respectively. The PCIBT-based OFET showed more dramatically enhanced μh and μe after the thermal annealing process than the 21



Page 22 of 37

PCITV-based OFET. These tendencies agree well with the analysis of molecular ordering and film morphology analysis in figure 3 and figure 4. In the case of PCIBT, remarkably enhanced molecular ordering, crystallinity, and shortened π-π stacking distance can be obtained from the thermal annealing process owing to the high rotational freedom of the polymer chain maximizing the chain rearrangement during the thermal annealing process. They enable the PCIBT film to have more effective intermolecular charge hopping between the polymer chains, which results in improved charge carrier mobility. However, in the case of PCITV with restricted rotational freedom, crystallinity is less affected by the thermal annealing, which leads to a lower charge carrier mobility than PCIBT.

Table 3. Top-gate/bottom-contact OFET characteristics. Polymer PCIBT PCITV a

TA [℃]

µh [cm2V-1S-1] a

VTh [V]

Ion/Ioff

µe [cm2V-1S-1] a

VTh [V]

Ion/Ioff

n/a

0.06 (0.07)

- 33.1

> 103

0.12 (0.14)

23.5

> 103

250

0.25 (0.38)

- 39.5

> 103

1.23 (1.7 )

35.4

> 104

n/a

0.07 (0.07)

- 33.0

> 103

0.08 (0.1 )

19.5

> 103

250

0.08 (0.1)

- 40.5

> 103

0.28 (0.39)

27.9

> 103

Maximum and average mobility values were calculated from at least five devices.

22


Page 23 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CONCLUSIONS In summary, we synthesized two CI acceptor based D-A type conjugated polymers with n-type dominant ambipolar charge transport characteristics. Although the two synthesised polymers exhibited similar crystallinity in pristine films, they showed different tendencies in molecular ordering and crystallinity depending on the donor properties after thermal annealing process. The molecular ordering and crystallinity of PCITV film were less influenced by the thermal annealing process owing to restricted rotational freedom induced by the rigid TV unit. However, large enhancements of molecular ordering and crystallinity were observed in the annealed PCIBT film because the more flexible nature of the BT unit can amplify thermal-assisted chain packing during the thermal annealing process. Improved crystallinity can facilitate the efficient intermolecular interactions, and, consequently, improve charge carrier mobility through increased intermolecular charge hopping. Thus, PCIBT showed enhanced electron mobility of up to 1.7 cm2V-1s-1. Our results demonstrated that chlorine-substituted isoindigo-based conjugated polymers can enhance the electron mobility through maximizing the thermal annealing effect by introducing a moiety having higher rotational freedom into the polymer backbone. We believe that our work provides an 23



Page 24 of 37

important design consideration of molecular design when using bulky monomers.

EXPERIMENTAL SECTION Synthetic procedures (E)-6,6`-dibromo-5,5`-dichloro-1,1`-bis(2-decyltetradecyl)-[3,3`-biindolinylidene]-2,2`dione (CI). N-chlorosuccinimide (NCS) (0.5 g, 3.8 mmol) was added to a solution of alkylated isoindigo (1.00 g, 0.7 mmol) in mixed solvent of chloroform (70 ml) and DMF (70 ml), and the mixture was stirred at 70 ℃ for 6 hours. After 6 hours, the reaction mixture was poured into water and extracted with chloroform. After removal the solvent under reduced pressure, the crude product was purified by silica gel chromatography with eluent (hexane : methylene chloride = 5 : 1) to give as a dark red solid (Yield: 0.48 g, 0.4 mmol, 59 %). 1H NMR (CDCl3, 400 MHz) δ: 9.40 (s, 2H), 6.99 (s, 2H), 3.62 (d, J = 7.41 Hz, 4H), 1.86 (s, 2H), 1.24 (m, 80H), 0.87 (m, 12H). 5,5'-bis(trimethylstannyl)-2,2'-bithiophene (BT). The 2,2’-Bithiophene (0.5 g, 3 mmol) was dissolved in 50 ml of distilled THF. After stirring for 20 min under -10 ℃, 7.5 ml of n-BuLi (1.6 M solution, 12 mmol) was dropped into the flask slowly and stirred for 1 h. The mixture

24


Page 25 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


was warmed to room temperature and stirred for 1h again. Then 9 ml of trimethyltin chloride (1 M, 9 mmol) was added at -10 ℃ and stirred overnight. The reaction mixture was poured into water and extracted with chloroform. After removal the solvent, the crude product was dried under high vaccum to afford as white powder (Yield: 0.88 g, 1.8 mmol, 60 %). 1H NMR (CDCl3, 400 MHz) δ: 7.51 (d, 2H), 7.14 (d, 2H), 0.27 (s, 18H). (E)-1,2-bis(5-(trimethylstannyl)thiophen-2-yl)ethene (TV). The (E)-1,2-di(thiophene-2yl)ethene (0.5 g, 2.6 mmol) was dissolved in 50 ml of distilled THF. After stirring 20 min at 10 oC, 6.5 ml of n-BuLi (1.6 M solution, 6.4 mmol) was dropped into the flask slowly and stirred for 1h. The mixture was warmed to room temperature and stirred for 1h again. Then 7.8 ml trimethyltin chloride (1 M, 7.8 mmol) was added at -10 oC and stirred overnight. The reaction mixture was poured into water and extracted with chloroform and recrystallization from isopropyl alcohol. After removal the solvent, the crude product was dried under high vaccum to afford as pale yellow powder (Yield: 0.8 g, 1.5 mmol, 52 %). 1H NMR (CDCl3, 400 MHz) δ: 7.12 (d, 2H), 7.09 (s, 2H), 7.07 (d, 2H), 0.38 (s, 18H). Stille polymerization of PCIBT. The CI (0.45 g, 0.4 mmol) and BT (0.19 g, 0.4 mmol) were dissolved in 20 ml of anhydrous toluene. The reaction flask was purged with nitrogen for 1 25



Page 26 of 37

h to remove the oxygen. Tris(dibenzylideneacetone)dipalladium (0.0073 g, 2 mol %), and tri(o-tolyl)phosphine (0.0146 g, 12 mol%) were added and heated to 110 ℃ for 30 min and end-capped with 2-bromobenzene and 2-(tri-n-butylstannyl)thiophene. The reaction was stopped and poured into 250 ml of methanol to reprecipitate and filtered. The polymer was washed with methanol, hexane, acetone, methylene chloride, chloroform, chlorobenzene using soxhlet extraction. Finally, polymer was obtained by chlorobenzene. The chlorobenzene solution was reprecipitated into 200 ml methanol and then filtered to afford 0.4 g as a dark solid (Yield: 0.4 g, 0.34 mmol, 85 %). Anal. Calcd (%): C, 74; H, 9.32; N, 2.4; S, 5.49; O, 2.74. Found (%): C, 73.94; H, 9.51; N, 2.43; S, 5.69; O, 2.8. Stille polymerization of PCITV. The CI (0.48 g, 0.4 mmol), and TV (0.21 g, 0.4 mmol) were dissolved in 20 ml of anhydrous toluene. The reaction flask was purged with nitrogen for 1 h to remove the oxygen. Tris(dibenzylideneacetone)dipalladium (0.0073 g, 2 mol %), and tri(o-tolyl)phosphine (0.0146 g, 12 mol%) were added and heated to 110 ℃ for 30 min and end-capped with 2-bromothiophene and 2-(tri-n-butylstannyl)thiophene. The reaction was stopped and poured into 250 ml of methanol to reprecipitate and filtered. The polymer was washed

with

methanol,

hexane,

acetone,

methylene

26


chloride,

chloroform

and

Page 27 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


chlorobenzene using soxhlet extraction. Finally, polymer was obtained by chlorobenzene. The chlorobenzene solution was reprecipitated into 200 ml methanol and then filtered to afford 0.45 g as a dark solid (Yield: 0.45 g, 0.38 mmol, 94 %). Anal. Calcd (%): C, 74.39; H, 9.28; N, 2.34; S, 5.37; O, 2.68. Found (%): C, 74.39; H, 9.27; N, 2.33; S, 5.35; O, 2.89. OFET Device Febrication. Top gate/bottom contact OFETs were fabricated. Au/Ni (15/3 nm) (Ni was the adhesion layer) were patterned as the source and drain electrodes [channel width (W): 1 mm, channel length (L): 10 ㎛] by conventional photolithography on Corning Eagle 2000 glass substrates. The patterned substrates were cleaned by using ultrasonication in deionized water, acetone, and isopropyl alcohol, and then the residual solvents in the substrates were dried in oven. Before spin-coating the polymer solution, the substrates were treated UV/ozone exposure for 15 min. Solution of conjugated polymers, PCIBT and PCITV, were produced by using trichloroethylene as a solvent with a concentration of 3 mg ml-1 and they were deposited onto a substrate to form a film with a thickness of ~20 nm under a nitrogen atmosphere. Then annealed polymer films were thermally annealed at 250 ℃ for 20 min. The PMMA (Aldrich, molecular mass of 120 kDa) was used for the polymer gate dielectric layers at a concentration of 80 mg ml-1 in n-butylacetate. The dielectric 27



solution were filtered with a 0.2 ㎛

Page 28 of 37

PTFE syringe filter and spin-coated onto the

semiconducting polymer layer (~ 480 nm). The gate leakage currents were provided in the supporting information (Figure S3). The films were subsequently baked at 80 ℃ for 1 h. Finally, the OFETs were completed by thermal evaporation of the Al gate electrode (~ 50 nm) using a metal shadow mask. The electrical characteristics of the fabricated OFET devices were measured using Keithley 4200-SCS instrument in a glove box under a nitrogen atmosphere. The μFET and VTh were calculated at the saturation region. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] ORCID Dong-Yu Kim: 0000-0003-2874-0329 Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the National Research Foundation of Korea (NRF) grant 28


Page 29 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


funded by the Korea government (NRF-2015R1A2A1A10054466) and Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20163030013900). The authors acknowledge the Korea Basic Science Institute (KBSI) for providing the AFM measurement. ASSOCIATED CONTENT Supporting Information. TGA, DSC, Transfer curve involving gate leakage current, δd-h2 curve

, top-gate/bottom-contact transistor device structure, and OFET characteristics of various annealing temperature. REFERENCES (1)

Chen, H.; Hurhangee, M.; Nikolka, M.; Zhang, W.; Kirkus, M.; Neophytou, M.; Cryer, S. J.; Harkin, D.; Hayoz, P.; Abdi-Jalebi, M.; McNeill, C. R.; Strringhaus, H.; McCulloch, I. Dithiopheneindenofluorene (TIF) Semiconducting Polymers with Very High Mobility in Field-Effect Transistors. Adv. Mater. 2017, 29, 1702523.

(2)

Lee, C.-H.; Lai, Y.-Y.; Hsu, J.-Y.; Huang, P.-K.; Cheng, Y.-J. Side-Chain Modulation of Dithienofluorene-Based Copolymers to Achieve High Field-Effect Mobilities.

Chem. Sci. 2017, 8, 2942–2951. (3)

Fei, Z.; Han, Y.; Gann, E.; Hodsden, T.; Chesman, A. S. R.; McNeill, C. R.; 29



Page 30 of 37

Anthopoulos, T. D.; Heeney, M. Alkylated Selenophene-Based Ladder-Type Monomers via a Facile Route for High-Performance Thin-Film Transistor Applications. J. Am. Chem. Soc. 2017, 139, 8552–8561. (4)

Park, W.-T.; Kim, G.; Yang, C.; Liu, C.; Noh, Y.-Y. Effect of Donor Molecular Structure and Gate Dielectric on Charge-Transporting Characteristics for IsoindigoBased Donor–Acceptor Conjugated Polymers. Adv. Funct. Mater. 2016, 26, 4695– 4703.

(5)

Lee, M.-H.; Kim, J.; Kang, M.; Kim, J.; Kang, B.; Hwang, H.; Cho, K.; Kim, D.-Y. Precise Side-Chain Engineering of Thienylenevinylene–Benzotriazole-Based Conjugated Polymers with Coplanar Backbone for Organic Field Effect Transistors and CMOS-like Inverters. ACS Appl. Mater. Interfaces 2017, 9, 2758–2766.

(6)

Jang, S.-Y.; Kim, I.-B.; Kim, J.; Khim, D.; Jung, E.; Kang, B.; Lim, B.; Kim, Y.-A.; Jang, Y. H.; Cho, K.; Kim, D.-Y. New Donor–Donor Type Copolymers with Rigid and Coplanar Structures for High-Mobility Organic Field-Effect Transistors. Chem. Mater. 2014, 26, 6907–6910.

(7)

Zhao, Z.; Yin, Z.; Chen, H.; Zheng, L.; Zhu, C.; Zhang, L.; Tan, S.; Wang, H.; Guo, Y.; Tang, Q.; Lui, L. High-Performance, Air-Stable Field-Effect Transistors Based on Heteroatom-Substituted Naphthalenediimide-Benzothiadiazole Copolymers Exhibiting Ultrahigh Electron Mobility up to 8.5 Cm V−1 S−1. Adv. Mater. 2016, 29, 1602410. 30


Page 31 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(8)


Back, J. Y.; Yu, H.; Song, I.; Kang, I.; Ahn, H.; Shin, T. J.; Kwon, S.-K.; Oh, J. H.; Kim, Y.-H. Investigation of Structure–Property Relationships in DiketopyrrolopyrroleBased Polymer Semiconductors via Side-Chain Engineering. Chem. Mater. 2015,

27, 1732–1739. (9)

Kim, G.; Kang, S.-J.; Dutta, G. K.; Han, Y.-K.; Shin, T. J.; Noh, Y.-Y.; Yang, C. A Thienoisoindigo-Naphthalene Polymer with Ultrahigh Mobility of 14.4 Cm2/V·s That Substantially Exceeds Benchmark Values for Amorphous Silicon Semiconductors. J.

Am. Chem. Soc. 2014, 136, 9477–9483. (10) Stalder, R.; Mei, J.; Graham, K. R.; Estrada, L. A.; Reynolds, J. R. Isoindigo, a Versatile Electron-Deficient Unit For High-Performance Organic Electronics. Chem.

Mater. 2014, 26, 664–678. (11) Zhang, G.; Dai, Y.; Song, K.; Lee, H.; Ge, F.; Qiu, L.; Cho, K. Bis(2-Oxo-7Azaindolin-3-Ylidene)Benzodifuran-Dione-Based Donor–acceptor Polymers for HighPerformance n-Type Field-Effect Transistors. Polym. Chem. 2017, 8, 2381–2389. (12) Di Pietro, R.; Sirringhaus, H. High Resolution Optical Spectroscopy of Air-Induced Electrical Instabilities in n-Type Polymer Semiconductors. Adv. Mater. 2012, 24, 3367–3372. (13) Shi, Y.; Guo, H.; Qin, M.; Zhao, J.; Wang, Y.; Wang, H.; Wang, Y.; Facchetti, A.; Lu, X.; Guo, X. Thiazole Imide-Based All-Acceptor Homopolymer: Achieving HighPerformance Unipolar Electron Transport in Organic Thin-Film Transistors. Adv. 31



Page 32 of 37

Mater. 2018, 30, 1705745. (14) Yuen, J. D.; Kumar, R.; Zakhidov, D.; Seifter, J.; Lim, B.; Heeger, A. J.; Wudl, F. Ambipolarity in Benzobisthiadiazole-Based Donor–Acceptor Conjugated Polymers.

Adv. Mater. 2011, 23, 3780–3785. (15) Shi, K.; Zhang, F.; Di, C.-A.; Yan, T.-W.; Zou, Y.; Zhou, X.; Zhu, D.; Wang, J.-Y.; Pei, J. Toward High Performance N-Type Thermoelectric Materials by Rational Modification of BDPPV Backbones. J. Am. Chem. Soc. 2015, 137, 6979–6982. (16) Sonar, P.; Fong Lim, J. P.; Chan, K. L. Organic Non-Fullerene Acceptors for Organic Photovoltaics. Energy Environ. Sci. 2011, 4, 1558–1574. (17) Zhao, Y.; Guo, Y.; Liu, Y. 25th Anniversary Article: Recent Advances in n-Type and Ambipolar Organic Field-Effect Transistors. Adv. Mater. 2013, 25, 5372–5391. (18) Lei, T.; Xia, X.; Wang, J.-Y.; Liu, C.-J.; Pei, J. “Conformation Locked” Strong Electron-Deficient Poly(p-Phenylene Vinylene) Derivatives for Ambient-Stable nType Field-Effect Transistors: Synthesis, Properties, and Effects of Fluorine Substitution Position. J. Am. Chem. Soc. 2014, 136, 2135–2141. (19) Zheng, Y.-Q.; Lei, T.; Dou, J.-H.; Xia, X.; Wang, J.-Y.; Liu, C.-J.; Pei, J. Strong Electron-Deficient Polymers Lead to High Electron Mobility in Air and Their Morphology-Dependent Transport Behaviors. Adv. Mater. 2016, 28, 7213–7219. (20) Lei, T.; Dou, J.-H.; Ma, Z.-J.; Yao, C.-H.; Liu, C.-J.; Wang, J.-Y.; Pei, J. Ambipolar

32


Page 33 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Polymer Field-Effect Transistors Based on Fluorinated Isoindigo: High Performance and Improved Ambient Stability. J. Am. Chem. Soc. 2012, 134, 20025–20028. (21) Yun, H.-J.; Kang, S.-J.; Xu, Y.; Kim, S. O.; Kim, Y.-H.; Noh, Y.-Y.; Kwon, S.-K. Dramatic Inversion of Charge Polarity in Diketopyrrolopyrrole-Based Organic FieldEffect Transistors via a Simple Nitrile Group Substitution. Adv. Mater. 2014, 26, 7300–7307. (22) Kang, S.-H.; Tabi, G. D.; Lee, J.; Kim, G.; Noh, Y.-Y.; Yang, C. Chlorinated 2,1,3Benzothiadiazole-Based Polymers for Organic Field-Effect Transistors.

Macromolecules 2017, 50, 4649–4657. (23) Lei, T.; Dou, J.-H.; Ma, Z.-J.; Liu, C.-J.; Wang, J.-Y.; Pei, J. Chlorination as a Useful Method to Modulate Conjugated Polymers: Balanced and Ambient-Stable Ambipolar High-Performance Field-Effect Transistors and Inverters Based on Chlorinated Isoindigo Polymers. Chem. Sci. 2013, 4, 2447–2452. (24) Hu, Z.; Chen, H.; Qu, J.; Zhong, X.; Chao, P.; Xie, M.; Lu, W.; Liu, A.; Tian, L.; Su, Y.-A.; Chen, W.; He, F. Design and Synthesis of Chlorinated BenzothiadiazoleBased Polymers for Efficient Solar Energy Conversion. ACS Energy Lett. 2017, 2, 753–758. (25) Chen, H.; Hu, Z.; Wang, H.; Liu, L.; Chao, P.; Qu, J.; Chen, W.; Liu, A.; He, F. A Chlorinated π-Conjugated Polymer Donor for Efficient Organic Solar Cells. Joule 2018, 2, 1623–1634. 33



Page 34 of 37

(26) Tang, M. L.; Oh, J. H.; Reichardt, A. D.; Bao, Z. Chlorination: A General Route toward Electron Transport in Organic Semiconductors. J. Am. Chem. Soc. 2009,

131, 3733–3740. (27) Oh, J. H.; Suraru, S.; Lee, W.-Y.; Könemann, M.; Höffken, H. W.; Röger, C.; Schmidt, R.; Chung, Y.; Chen, W.-C.; Würthner, F.; Bao, Z. High-Performance AirStable n-Type Organic Transistors Based on Core-Chlorinated Naphthalene Tetracarboxylic Diimides. Adv. Funct. Mater. 2010, 20, 2148–2156. (28) Kim, Y.-A.; Jeon, Y.-J.; Kang, M.; Jang, S.-Y.; Kim, I.-B.; Lim, D.-H.; Heo, Y.-J.; Kim, D.-Y. Structure-Property Relationship of D-A Type Copolymers Based on Thienylenevinylene for Organic Electronics. Org. Electron. 2017, 46, 77–87. (29) Lei, T.; Wang, J.-Y.; Pei, J. Design, Synthesis, and Structure–Property Relationships of Isoindigo-Based Conjugated Polymers. Acc. Chem. Res. 2014, 47, 1117–1126. (30) Kim, Y.; Hwang, H.; Kim, N.-K.; Hwang, K.; Park, J.-J.; Shin, G.-I.; Kim, D.-Y. πConjugated Polymers Incorporating a Novel Planar Quinoid Building Block with Extended Delocalization and High Charge Carrier Mobility. Adv. Mater. 2018, 30, 1706557. (31) Liu, J.; Mikhaylov, I. A.; Zou, J.; Osaka, I.; Masunov, A. E.; McCullough, R. D.; Zhai, L. Insight into How Molecular Structures of Thiophene-Based Conjugated Polymers Affect Crystallization Behaviors. Polymer (Guildf). 2011, 52, 2302–2309. (32) Fei, Z.; Boufflet, P.; Wood, S.; Wade, J.; Moriarty, J.; Gann, E.; Ratcliff, E. L.; 34


Page 35 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


McNeill, C. R.; Sirringhaus, H.; Kim, J.-S.; Heeney, M. Influence of Backbone Fluorination in Regioregular Poly(3-Alkyl-4-Fluoro)Thiophenes. J. Am. Chem. Soc. 2015, 137, 6866–6879. (33) Zhang, S.; Qin, Y.; Zhu, J.; Hou, J. Over 14% Efficiency in Polymer Solar Cells Enabled by a Chlorinated Polymer Donor. Adv. Mater. 2018, 30, 1800868. (34) Gao, Y.; Deng, Y.; Tian, H.; Zhang, J.; Yan, D.; Geng, Y.; Wang, F. Multifluorination toward High-Mobility Ambipolar and Unipolar n-Type Donor–Acceptor Conjugated Polymers Based on Isoindigo. Adv. Mater. 2017, 29, 1606217. (35) Lim, D.-H.; Jang, S.-Y.; Kang, M.; Lee, S.; Kim, Y.-A.; Heo, Y.-J.; Lee, M.-H.; Kim, D.-Y. A Systematic Study on Molecular Planarity and D–A Conformation in Thiazolothiazole- and Thienylenevinylene-Based Copolymers for Organic FieldEffect Transistors. J. Mater. Chem. C 2017, 5, 10126–10132. (36) Elandaloussi, E. H.; Frère, P.; Richomme, P.; Orduna, J.; Garin, J.; Roncali, J. Effect of Chain Extension on the Electrochemical and Electronic Properties of πConjugated Soluble Thienylenevinylene Oligomers. J. Am. Chem. Soc. 1997, 119, 10774–10784. (37) Fu, Y.; Cheng, H.; Elsenbaumer, R. L. Electron-Rich Thienylene−Vinylene Low Bandgap Polymers. Chem. Mater. 1997, 9 (8), 1720–1724. (38) Hosemann, A. M. H. and R. Paracrystals Representing the Physical State of Matter.

J. Phys. C Solid State Phys. 1988, 21, 4155. 35



Page 36 of 37

(39) Yoo, D.; Nketia-Yawson, B.; Kang, S.-J.; Ahn, H.; Shin, T. J.; Noh, Y.-Y.; Yang, C. A Timely Synthetic Tailoring of Biaxially Extended Thienylenevinylene-Like Polymers for Systematic Investigation on Field-Effect Transistors. Adv. Funct. Mater. 2014, 25, 586–596. (40) Sun, B.; Hong, W.; Yan, Z.; Aziz, H.; Li, Y. Record High Electron Mobility of 6.3 Cm2V−1s−1 Achieved for Polymer Semiconductors Using a New Building Block.

Adv. Mater. 2014, 26, 2636–2642. (41) Lei, T.; Cao, Y.; Fan, Y.; Liu, C.-J.; Yuan, S.-C.; Pei, J. High-Performance Air-Stable Organic Field-Effect Transistors: Isoindigo-Based Conjugated Polymers. J. Am.

Chem. Soc. 2011, 133, 6099–6101. (42) Mei, J.; Kim, D. H.; Ayzner, A. L.; Toney, M. F.; Bao, Z. Siloxane-Terminated Solubilizing Side Chains: Bringing Conjugated Polymer Backbones Closer and Boosting Hole Mobilities in Thin-Film Transistors. J. Am. Chem. Soc. 2011, 133, 20130–20133. (43) Shin, J.; Um, H. A.; Lee, D. H.; Lee, T. W.; Cho, M. J.; Choi, D. H. High Mobility Isoindigo-Based π-Extended Conjugated Polymers Bearing Di(Thienyl)Ethylene in Thin-Film Transistors. Polym. Chem. 2013, 4, 5688–5695.

36


Page 37 of 37 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of Contents

37


Chlorinated Isoindigo-Based Conjugated Polymers: Effect of

Recommend Documents