Design of New Isoindigo Based Copolymer for Ambipolar Organic

Subscriber access provided by UNIVERSITY OF CONNECTICUT

Organic Electronic Devices

Design of New Isoindigo Based Copolymer for Ambipolar Organic Field-Effect Transistors Eun-Sol Shin, Yeon Hee Ha, Eliot Gann, Yun-Ji Lee, SoonKi Kwon, Christopher R. McNeill, Yong Young Noh, and Yun-Hi Kim ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03131 • Publication Date (Web): 02 Apr 2018 Downloaded from http://pubs.acs.org on April 2, 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 27 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 Materials & Interfaces

Design of New Isoindigo Based Copolymer for Ambipolar Organic Field-Effect Transistors Eun-Sol Shin, Yeon Hee Ha, Eliot Gann, Yun-Ji Lee, Soon-Ki Kwon, Christopher R. McNeill, Yong-Young Noh*, and Yun-Hi Kim* Prof. Y.-Y. Noh, E.-S. Shin Department of Energy and Materials Engineering, Dongguk University, 30 Pildong-ro, 1-gil, Jung-gu, Seoul 100-715, Republic of Korea E-mail:[email protected] Prof. Y.-H. Kim, Yeon Hee Ha Department of Chemistry, Gyeongsang National University and RIGET, 900, Gajwa-dong, Jinju, Gyeongnam 660-701, Republic of Korea E-mail:[email protected] Prof. S.K. Kwon, Yun-Ji Lee Department of Materials Engineering and Convergence Technology and ERI, 900, Gajwa-dong, Jinju, Gyeongnam 660-701, Republic of Korea Prof. C.R. McNeill, Dr. E. Gann Department of Materials Science and Engineering, Monash University, Wellington Road, Clayton, VIC 3800, Australia Dr. E. Gann Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia Keywords: Organic field effect transistors, conjugated polymers, isoindigo, planarity of conjugated polymers, charge carrier mobility

1 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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 27

ABSTRACT: We report the synthesis of a new conjugated polymer composed of isoindigo (IID) and 2,3-bis[thiophenyl-2-yl]thiophene acrylonitrile (CNTVT) subunits for high performance ntype organic field-effect transistors (OFETs). To realize high electron mobility for the IID-based conjugated polymer, an electron withdrawing nitrile group is incorporated into the vinylene unit, thereby shifting the energy of the lowest unoccupied molecular orbital for efficient electron injection from Au electrodes without disrupting backbone planarity. Uniaxially-aligned IID24CNTVT conjugated polymer films for efficient intramolecular charge transport are achieved by off-center spin coating from pre-aggregated solutions. In order to obtain its stable pre-aggregation in solution, a binary solvent system (a mixture of good and bad solvents) chosen with the assistance of Hansen solubility parameter simulation is used. Through this process, highly aligned IID24CNTVT films are obtained by off-center spin coating from a solvent mixture of 9:1 dichlorobenzene:2-methoxyethanol as the good and bad solvents, respectively. The properties of the aligned IID24-CNTVT films are characterized with various analytical techniques, including UV-visible absorption spectroscopy, angle-resolved near edge X-ray absorption fine structure spectroscopy, and grazing-incidence wide-angle X-ray scattering. Top-gate/bottom-contact OFETs with IID24-CNTVT films aligned in the direction of charge transport exhibit a high electron field-effect mobility of 0.83 ± 0.13 cm2/Vs.


Page 3 of 27 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


INTRODUCTION Organic field-effect transistors (OFETs) are attractive as they are extremely lightweight, flexible, and wearable electronics on plastic substrates produced by cost effective printing processes such as spin, bar, and roll-to-roll coating, and inkjet printing.1-8 Recently, field-effect mobility (μ) of solution-processed OFETs exceeding > 10 cm2V–1s–1 have been brought about through the development of novel organic semiconductors (OSCs) and gate dielectrics in combination with optimization of crystallinity, molecular ordering, and the interface between metal contacts and the OSC.9-16 In particular, impressive enhancements in μ have been achieved by highly planar conjugated polymer films with uniaxial alignment through various methods in the same direction as the channel of transistors. 17-19 The alignment of the polymer chains is strongly influenced by the structure of the conjugated polymer, the solution state of the polymer, and the coating method. In order to form highly aligned conjugated polymer films, a stable pre-aggregated solution must first be obtained by careful selection of the solvents.20-22 OFETs fabricated from pre-aggregated polymer solutions have shown dramatically improved and largely anisotropic μ compared to OFETs fabricated from well-dissolved polymer solutions.23-24 Furthermore, a strong force should be applied to the preaggregated solution in one direction to align the polymer chains during the film coating process.2528

Therefore, understanding the conditions for preparing appropriate pre-aggregates in solution is

needed to infer proper design of the side-chain structure and to establish selection rules for the solvents. In addition, several coating methods such as off-center spin coating or directional coating have been suggested to form highly aligned polymer chain films.29-31



Page 4 of 27

OSCs made from donor-acceptor (D-A) type conjugated polymers are emerging due to their broad absorption spectra with high absorption coefficients suitable for photovoltaic application and high charge mobility suitable for OFETs.32-38 Among the various building blocks for D and A units, isoindigo (IID), which is naturally obtained from indigo pigment, is easily synthesized, relatively cheap, and environmentally friendly.37, 39 The electron-deficient ketopyrrole core and off-axis dipole moment of the isoindigo structure is used to improve intermolecular interactions and ambient stability, the latter being imparted through the generally low-lying highest occupied molecular orbital (HOMO) levels. Recently, high p-type charge carrier mobility has been reported in IID-based polymers produced by selenophene substitution and side-chain engineering.3, 40-41 However, a few reports have shown the n-type characteristics of IID-based polymers with high electron mobility being much smaller than that of the holes.42-43 In this paper, we report the design and synthesis of a new IID-based conjugated polymer (IID24-CNTVT) for high performance n-channel OFETs by employing 2,3-bis[thiophenyl-2yl]thiophene acrylonitrile (CNTVT). The incorporation of a nitrile group in the vinylene unit resulted in enabling efficient electron injection from a commonly used Au electrode without sacrificing backbone planarity. To achieve high performance n-channel OFETs, we investigated the solvent selection rule for preparing highly stable pre-aggregated solutions with the solvent properties tuned by varying the mixing ratio of good and bad solvents in a binary solvent system. Highly aligned IID24-CNTVT films were achieved by off-center spin coating from a solvent mixture of dichlorobenzene (DCB) as a good solvent and 2-methoxyethanol (2-ME) as a bad solvent with a 9 to 1 volume ratio, and OFETs made with the aligned IID24-CNTVT films exhibited a high electron μ of 0.83 ± 0.13 cm2/V·s. Various analysis techniques were used to investigate the degree of alignment in the polymer film, namely UV-visible (UV-vis) absorption spectroscopy,


Page 5 of 27 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


angle-resolved near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and grazingincidence wide-angle x-ray scattering (GIWAXS). RESULTS Characteristics of IID24-CNTVT. The synthesis scheme for IID24-CNTVT is depicted in Figure S1 of the supporting information. IID24-CNTVT was synthesized by the reaction of 6,6’-dibromo-(N,N’-2-decyltetradecyl)isoindigo and (E)-2,3-bis(5-(trimethylstannyl)thiophene-2-yl)acrylonitrile via Stille coupling. IID24-CNTVT was purified by sequential Soxhlet extraction with methanol, acetone, hexane, and chloroform. The chemical structure of the polymer was confirmed by proton nuclear magnetic resonance (1H-NMR; Figure S2). The number average molecular weight of IID24-CNTVT was 66 kg/mol with a polydispersity index of 2.15 as determined by gel permeation chromatography (GPC) measurements (Figure S3). To investigate the backbone planarity, and HOMO and lowest unoccupied molecular orbital (LUMO) levels, density functional theory (DFT) calculations were carried out using B3LYP 6-311G** for full geometry. The dihedral angles between the IID unit and the adjacent thiophene units of IID24-CNTVT were similar to those of IID24-TVT (Figures 1 and S4). The calculated HOMO and LUMO energy levels of IID24-CNTVT were -5.43 eV and 3.33 eV, which are both deeper than the respective HOMO and LUMO energy levels of IID24TVT (Figure S5). The HOMO and LUMO levels of IID24-CNTVT were experimentally measured as -5.17 eV and -3.97 eV, respectively, by cyclic voltammetry (Figure S6). Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) thermograms of IID24-CNTVT showed that it was thermally stable up to 425 ºC without thermal transitions (Figure S7).



Page 6 of 27

Figure 1. The molecular structure and 3D-structure with dihedral angles of the IID24-CNTVT polymer. Figure 2 presents the UV-vis absorption spectra of IID24-CNTVT in solution (chloroform as a solvent) and as a thin film (both as-cast and annealed film at 175 ℃). IID24-CNTVT showed the typical dual band absorption spectrum for a D-A polymer. Band I (600-800 nm) with three vibrational peaks corresponding to the intramolecular charge transfer absorption between IID and CNTVT, while band II corresponding to  to * absorption was found at around 470 nm. When comparing solution and solid-state absorption spectra, we can see a subtle increase in the 0–0 absorption peak intensity and a decrease in the 0–1 absorption peak intensity, which are attributed to rearrangement of the polymer chains during film formation. These relative changes of 0–0 and 0–1 peak intensity were greater for IID24-CNTVT than for IID24-TVT polymer without CN (Figure S8), thus indicating that IID24-CNTVT had greater intermolecular interactions in the thin-film state compared to IID24-TVT. Their UV-absorption spectra are similar except for a 10-20 nm redshifting of the vibrational peaks of IID24-CNTVT. This larger red shift indicates that IID24-CNTVT has a more planar backbone compared to IID24-TVT.40 The maximum absorption peak (λmax) of the IID24-CNTVT solution showed negligible difference with bare and annealed film, signifying the formation of a strong aggregation of polymers in chloroform. In addition, the observed same λmax in as-cast and annealed films indicates that the ordering in the polymer film did not change significantly with thermal annealing. Hansen solubility parameter.


Page 7 of 27 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. The UV-vis absorption spectra of IID24-CNTVT in CHCl3, and in thin film (both as-cast and annealed film at 175 °C). To quantitatively investigate the degree of stable pre-aggregation facilitating the formation of wellaligned polymer films, we performed Hansen solubility parameter (HSP) analysis of binary solvent systems composed of good (DCB) and bad solvents (2-ME) for IID24-CNTVT. The aggregation of the semiconductor on film surfaces was observed by atomic force microscopy (AFM). The films deposited by solutions with well-dispersed polymers in 10:0 (DCB:2-ME) solvents showed small size of domains. And we observed larger size of domain on film surface deposited by preaggregated solutions in 9:1 and 8:2 (DCB:2-ME) than 10:0 (DCB:2-ME) sample. Hansen separated the solubility parameter of a polymer into three contributions: atomic dispersive forces (δD), molecular permanent dipole-permanent dipole polar interactions (δP), and molecular hydrogen-bonding interactions (δH).44 These parameters are related to the overall solubility parameter δ by the following equation: δ2 = δ2 D + δ2 P + δ2 H .

(1)



Page 8 of 27

Figure 3. The Hansen solubility parameter data for IID24-CNTVT: (a) Hansen sphere of IID24CNTVT and the HSP values of 39 solvents (details of the solvents are described in Table S1) and (b) the chemical structures of DCB and 2-ME, and the Hansen parameter values of the polymer and the two chosen solvents in plots of (c) atomic dispersive forces (D) versus hydrogen-bonding interactions (H) and (d) dipole polar interactions (P) versus hydrogen-bonding interactions (H).

We calculated the HSPs of the IID24-CNTVT polymer using software developed by Abbott and Hansen45 from the solubility data of the polymer dissolved in thirty nine different solvents at 80 ℃ (Table S1). The solubility was characterized as either 0 for an insoluble solvent or 1 for a soluble solvent as judged by visual inspection. From this analysis IID24-CNTVT was determined to have δD = 18.17, δP = 4.10, and δH = 4.0 Mpa1/2, and Hansen sphere radius (R0) of 5.1. The relative


Page 9 of 27 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


energy difference (RED), which refers to the distance of a solvent from the center of Hansen space, was also calculated. The distance between a solvent and polymer in Hansen space (Ra) is derived from the Hansen parameters (δDi, δPi, and δHi) of the polymer and the solvent with a pre-factor of 4 for the dispersive component. The RED between solute and solvent is then defined as Ra divided by R0. The soluble and insoluble characteristics of a polymer in various solvents can be predicted based on this RED value induced by Hansen parameters as Ra2=4(δD2-δD1)2+(δP2-δP1)2+(δH2-δH1)2 RED = Ra/R0.

(2) (3)

A RED value of 0 indicates that the polymer has completely dissolved in the solvent, while a RED value means the solvent is on the surface of the Hansen sphere and will only partially dissolve the polymer, and solvents with a RED value of over 1 will not dissolve the polymer. In contrast, a RED value of less than 1 indicates that the polymer will be dissolved in the solvent. Figure 3a shows the Hansen sphere of IID24-CNTVT and HSPs of various solvents in 3-dimensional space. The solvents inside (blue points) and outside (red points) of the Hansen sphere indicate good and bad solvents, respectively, for IID24-CNTVT. Based on this, we selected DCB and 2-ME as respective good and bad solvents for the binary solvent system (their chemical structures are shown in Figure 3b). Another reason to select these two solvents was the distance of the Hansen parameter between the polymer and solvents depending on different ratios of the solvents. DCB and 2-ME with a 9 to 1 ratio had the shortest distance and with 7 to 3 had the longest distance between the polymer and solvents; δD comes from van der Waals forces correlated by interactions between charge variations in the electron distribution of atoms and are well known to be weaker than hydrogen bonding.46 In the binary solvent system with DCB and 2-ME, δD decreased from 19.2



Page 10 of 27

for pure DCB to 18.2 for a 7:3 ratio of DCB:2-ME, while the δp force increased from 6.3 for pure DCB to 6.9 for a 7:3 ratio of DCB:2-ME. The largest change by adding the bad solvent (2-ME) was observed in the δH force of the binary solvent, which increased from 3.3 for pure DCB to 6.8 for a 7:3 ratio of DCB:2-ME, showing that δH is an important variable to help decide solution characteristics using the Hansen parameters. The correlation of molecular interactions between IID24-CNTVT and each binary solvent mixture is shown in Figure 3d. We can expect the degree of aggregation from these molecular interaction parameters. The short distance of polymer and binary solvents in Figure 3 (c) and (d) indicate that the polymer was well dispersed whereas the strongest aggregation state was expected to occur with the longest distance. The distance of δH (ΔH) and δP (ΔP) between IID24-CNTVT polymer and each binary solvents ratio is 2.66, 2.64, 3.10, and 3.90 for ratios of 10:0, 9:1, 8:2, and 7:3, respectively. In Table S2, the RED value for the polymer in a 9:1 ratio of DCB and 2-ME is 0.71. In a previous report, RED values from 0.4 to 0.7 showed the highest carrier mobility and high dichroic ratios of OFETs fabricated by off-center spin coating of the polymer.47 Thus, we expected the highest alignment of polymer chains at the 9:1 ratio, which had a molecular interaction value of 2.64 and a RED value of 0.71 for the polymer in the DCB and 2-ME binary solution. Characterization of IID24-CNTVT films depending on the degree of alignment. We measured polarized UV-vis absorption spectra to investigate the optical dichroic ratios of aligned films from off-center spin-coated polymer in the binary solvent at different ratios of 10:0, 9:1, 8:2, and 7:3 by volume (Figure 4). The degree of alignment can be estimated by comparingabsorption spectra acquired with light polarized either parallel or perpendicular to the alignment direction induced by the off-center spin-coating process, and the optical dichroic ratio


Page 11 of 27 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. The optical dichroic ratios for the aligned off-center spin-coated IID24-CNTVT films at different solvent ratios: (a) illustration of the off-center spin coating process with different alignment directions (perpendicular and parallel); polarized UV−vis absorption spectra of the films in DCB:2-ME at (b) 10:1 (c) 9:1 (d) 8:2, and (e) 7:3, and (f) optical dichroic ratios for DCB:2-ME at 10:0, 9:1, 8:2, and 7:3. is calculated as the ratio of the absorption intensity at λmax (~710 nm) for the parallel and perpendicular orientations. The dichroic ratio was determined as 1.02, 1.73, 1.48, and 1.1 for films from the polymer in binary solvents with DCB and 2-ME ratios of 10:0, 9:1, 8:2, and 7:3, as shown in Figure 4d. The largest dichroic ratio at a solvent ratio of 9:1 was obtained by forming proper and stable pre-aggregation by controlling solubility since the other parameters used to determine film quality such as boiling point, dipole moment, and viscosity were almost constant in the binary solvent system. The stable pre-aggregated polymers can take more centrifuge force in one direction from off-center spin coating compared to well dissolved polymers in solution state. The the ratio between the absorption intensity for the paralle and perpendicular direction of polymer in polarized UV-vis absorption spectra is increased depending on the degree of polymer alignment on the surface.



Page 12 of 27

Figure 5. Plots of angle-resolved NEXAFS spectra of aligned (a-c) IID24-CNTVT thin films and (d-f) π* resonance intensity as a function of azimuthal angle for (a,d) 10:0, (b,e) 9:1, and (c,f) 8:2 binary solvent ratios. All NEXAFS spectra were acquired with normal incidence of the X-ray beam. Figure 5 shows NEXAFS spectra taken of off-center spin-coated IID24-CNTVT films fabricated with binary solvents DCB and 2-ME. These spectra were taken with the polarized X-ray beam normally incident to the samples and the samples azimuthally rotated. Dichroism was observed at both π* (~ 285 eV) and σ* (~ 290 to 310 eV) resonances (associated with the alignment of the polymer backbones in the plane of the film) due to changes in the orientation of 1s  π* and 1s  σ* transition dipole moments.48 Figure 5 a-c presents the carbon K-edge spectra of the samples as a function of azimuthal angle, while Figure 5 d-f contains plots of changes in π* resonance intensity as a function of azimuthal angle and clearly show a cosine-squared dependence indicating a degree of alignment of the polymer chains. To estimate this for each polymer film, the NEXAFS dichroic ratio was calculated as the ratio of the maximum π* resonance intensity over the minimum


Page 13 of 27 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 6. AFM images at 5×5 μm scan area of the IID24-CNTVT film in on center spin coating process with (a) 10:0, (b) 9:1 and (c) 8:2 solvents ratio and in off center spin coating process with (d) 10:0, (e) 9:1 and (f) 8:2 solvents ratio (DCB:2-ME). π* resonance intensity, giving values of 1.3, 2.1, and 1.9 for the 10:0, 9:1, and 8:2 samples, respectively. In general, these values were higher than those measured optically, suggesting that the degree of alignment at the top surface was greater than that in the bulk of the film (NEXAFS is a surface sensitive technique with a sampling depth of ~ 3 to 5 nm for total electron yield mode). However, surface sensitive measurements of backbone alignment are more relevant for the operation of top-gate transistors. Similar to the optical measurements, the highest dichroic ratio was observed for the 9:1 sample. GIWAXS was performed to understand the bulk alignment of the polymer chains (Figure S9) with data taken with the X-ray beam directed either parallel or perpendicular to the alignment direction. All IID24-CNTVT films showed intense out-of-plane (qz) diffraction peaks, indicating strong edge-on orientation of the polymer chains. The (100) first order lamellar stacking peak was



Page 14 of 27

observed at qz ~ 0.27 Å-1, corresponding to a lamella d-spacing of ~ 23.5 Å. A prominent in-plane π-π stacking peak was also observed at ~ 1.75 Å-1, corresponding to a π-π stacking distance of 3.59  0.02 Å, which is relatively smaller than previous reported for DPP-and IID-based D-A polymers (3.6 Å ~ 3.8 Å).49-50 Therefore, we expected IID24-CNTVT to have high charge carrier mobility. Comparing the scattering data taken parallel and perpendicular to the alignment direction, clear differences can be seen in the in-plane scattering while little change is seen in the out-ofplane scattering. In particular, the intensity of the π-π stacking peak is much greater in the scattering patterns taken with the X-ray beam parallel to the alignment direction, especially for the 9:1 and 8:2 samples. However, little change is seen in the intensity of the π-π stacking peak of the 10:0 sample, suggesting a poor degree of alignment and consistent with the optical and NEXAFS results. In principle, the degree of alignment can be assessed by comparing the peak area of the ππ stacking peak in the parallel and perpendicular data sets, but scattering intensity in a GIWAXS experiment is sensitive to many other parameters such as the beam footprint along the sample; it is also especially sensitive to the angle of incidence and hence, the alignment of the sample with respect to the beam. Nevertheless, from the dataset in Figure S9, a value of 2.3 was calculated from the ratio of the π-π stacking peak areas of the 9:1 sample and a value of 3.2 was calculated from the ratio of the π-π stacking peak areas of the 8:2 sample. This suggests that the polymer crystallites may actually be more aligned in the case of the 8:2 sample. In any case, we can confirm that GIWAXS was able to indicate the alignment of the polymer chains in the cases of the 9:1 and 8:2 ratio samples, and only a small degree of alignment observed for the 10:0 ratio sample. But surface sensitive measurements of backbone alignment are more relevant for the operation of topgate transistors. The high performance transistor can achieved in 9:1 ratio condition which have highest dichroic ratio in NEXAFS measurement.


Page 15 of 27 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


Atomic force microscopy (AFM) is measured to confirm the alignment in the IID24CNTVT films fabricated by on and off- center spin coating process. (Figure 6) The AFM results show the 9:1 ratio (Figure 6e) has more aligned domains than the 8:2 and 10:0 following the direction of centrifuge force, which is consistent with the results of polarized UV-vis absorption spectra and NEXAFS. And we measured the thickness of the films by AFM. The thickness of the films spin coated in off center process are twice as thin as the films formed by on center spin coating process. The thickness of films are 20.0, 6.4 and 3.7 nm in off center process and 43.5, 16.0 and 7.2 nm in on center process for 10:0, 9:1 and 8:2 solvents. Because much more centrifuge force influence the solution on the substrate in off-center spin coating, the thickness of films in off center spin coating is thinner than on center spin coating. In addition, we observed a smoother surface measured by root mean square roughness (RMS) in off center for 10:0 (10.0 nm), 9:1 (3.6 nm) and 8:2 (0.7 nm) compared to the on-center for 10:0 (19.6 nm), 9:1 (5.0 nm) and 8:2 (1.2 nm). The thickness and surface roughness of the films are related to the coating condition. However, from the performance of OFETs fabricated using 10:0, 9:1 and 8: 2 solvents and on-center spin coating, we can expect these to have no significant effect on device performance. While OFET produced with on-center spin coating with an 8:2 solvent shows the lowest mobility, the films coated in the on-center spin coating process show a thinner thickness and a smoother surface than other solvents. This indicates that polymer alignment is a more important factor in device performance.



Page 16 of 27

Figure 7. Illustration of the device structure using IID24-CNTVT as a semiconductor and PMMA as a dielectric materials.

Figure 8. Transfer characteristics of OFETs fabricated by off center spin coating with different directions (parallel and perpendicular) and solutions with different solvent ratios: (a) 10:0, (b) 9:1, (c) 8:2, and (d) 7:3 (DCB:2-ME). (e) Average electron carrier mobility of devices with parallel and perpendicular at the saturation region. Characterization of OFETs.


Page 17 of 27 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 8 and Figure S10 show typical transfer plots of top-gate/bottom-contact IID24-CNTVT OFETs (Figure 7) fabricated by on- and off-center spin coating from binary solvents with 10:0, 9:1, 8:2, and 7:3 ratios of DCB and 2-ME. The output plots in figure S11 demonstrate the characteristic dependence of IDS on VDS and VGS expected for amipolar devices. All IID24-CNTVT OFETs showed typical ambipolar characteristics with higher mobility for electrons than holes and Table 1. Dichroic ratio parameters calculated from polarized UV-vis spectra, I-V characteristics, and NEXAFS spectra with different solvent ratios. DCB:2-ME

Optical dichroic ratio

Electrical dichroic ratio

NEXAFS dichroic ratio

10:0

1.02

1.9

1.3

9:1

1.73

2.52

2.1

8:2

1.48

2.5

1.9

7:3

1.3

20

-

(v/v ratio)

better device performance with the films aligned parallel to the transport direction as opposed to perpendicular. The highest electron mobility (µe, Max = 1.07 cm2/V∙s) was achieved in the parallel direction with a 9:1 solvent ratio. To compare the anisotropy of charge transport, we calculated the electrical dichroic ratio extracted from the OFET data for each solvent ratio as 1.9, 2.52, 2.5, and 20 for 10:0, 9:1, 8:2, and 7:3, respectively. Exceptionally, in the case of the 7:3 solvent ratio, the film was not uniformly coated and the performance of the OFETs with perpendicularly aligned film was dramatically decreased. Moreover, its electrical dichroic ratio dramatically increased but this became meaningless due to very low absolute mobility. Thus from this point, we will exclude the 7:3 sample from the discussion. All of the dichroic ratio values that were measured by I-V, polarized UV-vis absorption, and NEXAFS spectroscopy are summarized in Table 1 (for the case of the 7:3 ratio, reliable NEXAFS data could not be extracted due to the non-uniformity of the film). This comparison revealed that the optical and NEXAFS dichroic ratios tended to be similar



Page 18 of 27

to the electrical dichroic ratio. From all measurements, the largest dichroic ratio was achieved with the 9:1 solvents ratio. Furthermore, we observed the second largest dichroic ratio with the 8:2 solvent ratio and the third largest value for the 10:0 solvent ratio. These results taken together indicate that the performance of IID24-CNTVT OFETs depended strongly on the degree of polymer Table 2. Parameters of OFETs depending on solution conditions and different directions in offcenter spin coating. μe, Max (cm2/V∙s)

μe, avg (dichroic ratio) (cm2/V∙s)

VT (V)

μh, avg (cm2/V∙s)

on/off ratio

Parallel

0.67

0.59 ± 0.07 (1.9)

41

0.28 ± 0.09

7×10

Perpendicular

0.36

0.31 ± 0.04

38

0.13 ± 0.03

9×10

DCB : 2-ME (v/v ratio) 10:0

Parallel

1.07

Perpendicular

0.39

Parallel

0.61

Perpendicular

0.19

Parallel

6×102

42

0.26 ± 0.07

37

0.13 ± 0.02

43

0.15 ± 0.03

0.18 ± 0.01

36

0.07 ± 0.005

9×10

0.21

0.16 ± 0.05 (20)

50

0.05 ± 0.017

1×102

Perpendicular

0.01

0.008 ± 0.002

49

0.003 ± 0.001

1×102

On center

NA

NA

-2

0.86 ± 0.16

9:1 IID24CNTVT

0.83 ± 0.13

8:2

(2.52) 0.33 ± 0.06 0.45 ± 0.08 (2.5)

3×102 1×102

7:3

IID24TVT40

-

alignment, particularly at the surface of the film. The best average electron carrier mobility of 0.83 ± 0.13 cm2/V·s (the highest value of 1.07 cm2/V·s) and the largest on off ratio (6×102) was achieved for the 9:1 solvent ratio film aligned parallel to the charge transport direction (Table 2). In the perpendicular direction, the average electron carrier mobility of the OFETs was only 0.33 ± 0.06 cm2/V·s, roughly 2.5 times lower than the parallel ones. This large electric anisotropy


Page 19 of 27 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


indicates that electrons mainly transported through extended LUMO orbitals in highly aligned polymer backbones. The hole carrier mobility of the OFETs shows the similar behavior with electron carrier mobility. The average hole carrier mobility of 0.13 ± 0.03 cm2/V·s in parallel direction show roughly 2 times lower than the parallel one (0.28 ± 0.03 cm2/V·s) in 10:0 ratio of solvents. Interestingly, hole mobility did not improve for the 9:1 sample aligned from the good solvent only. This means that the holes mainly transport through interchain hopping between randomly distributed HOMO frontier orbitals. On increased addition of bad solvent, electron carrier mobility decreased in both the parallel and perpendicular directions. However, as the ratio of bad solvent is increased for the on-center spin-coated samples, the mobility decreases gradually (Figure S12 and Table S3). CONCLUSIONS In conclusion, we developed a new copolymer, IID24-CNTVT, based on IID and CNTVT subunits. The sacrificing introduction of a nitrile group into the vinylene unit facilitated the realization of nchannel transistors without backbone planarity and thin film crystallinity. Indeed, IID24-CNTVT was found to have increased back bone planarity with red-shifted UV-absorption relative to other IID polymers. We investigated the most suitable solution to produce highly aligned polymer films by adopting a binary solvent system to enable the tuning of the pre-aggregation. HSP analysis was performed to quantify the goodness of the solvent system whereby solutions with a RED value of 0.71 were expected to achieve a high degree of pre-aggregation in solution. Using a binary solvent system based on DCB (good) and 2-ME (bad) solvents, the alignment of IID24-CNTVT films was achieved with off-center spin coating, as confirmed by UV-vis and NEXAFS spectroscopy. The highest degree of alignment was achieved for films coated from a 9:1 DCB:2-ME solvent ratio solution. The performance of IID24-CNTVT transistors was also the when IID24-CNTVT films



Page 20 of 27

were coated from the 9:1 solvent ratio solution, with significantly higher mobility observed along the parallel alignment direction of the polymer. This work provides a systematical approach to implementing high performance transistors using novel D-A polymers with high planarity. EXPERIMENTAL METHODS OFETs Fabrication and Device Characterization OFETs with a top-gate/bottom-contact structure were fabricated on glass substrates with a prepatterned Au/Ni electrode. Before spin coating the polymer, the glass substrates were cleaned with deionized water, acetone, and isopropanol for 10 min each in an ultrasonic bath and treated with UV for 30min. IID24-CNTVT polymer solutions (5mg/ml) dissolved in binary solvents with different ratios (DCB:2-ME = 10:0, 9:1, 8:2, 7:3) and various solvents (DCB, mesitylene, and toluene) were prepared for making thin film using on- and off-center spin-coating processes at 1500 rpm for 60 s. In off center spin coating process, the distance between substrate and the center is 2 cm. The annealing temperature of film is 310℃ for 30 min in an N2-filled glove box. Polymethylmethacrylate (PMMA) polymer in n-butyl acetate (80 mg/ml) was filtered using a 0.2 mm polytetrafluoroethylene (PTFE) syringe filter and on-spin coated onto the polymer layer at 2000 rpm for 60 s as a dielectric material in an N2-filled glove box, and the films were then annealed at 80 ℃ for 2 h in the same atmosphere. Al film with shadow mask was deposited onto the active layer of the transistors as a gate electrode using thermal evaporation. The electrical characteristics of the OFETs were measured using a semiconductor characterization system (Keithley 4200-SCS) in an N2-filled glove box. The field-effect mobility (μFET) and threshold voltage (VT) were derived from equations for classical silicon metal–oxide–semiconductor fieldeffect transistors in the saturation regime. The UV–vis spectra in film and solution states were


Page 21 of 27 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


measured with a UV-vis spectrometer (JASCO V-650), and polarized film was used in front of the source beam for polarized UV-vis spectra.

NEXAFS NEXAFS spectroscopy was performed at the Soft X-ray beamline of the Australian Synchrotron.51 Samples were measured in an ultra-high vacuum chamber with X-ray absorption measured by recording the drain current flowing to the sample (so-called total electron yield (TEY) mode. The incident X-ray flux was measured using a gold-coated mesh with carbon contamination on the mesh calibrated by measuring the direct beam signal at the sample position with a photodiode. Energy was calibrated with reference to the excitonic peak of a highly oriented pyrolytic graphite sample. The measured spectra were doubled-normalized using procedures described elsewhere, 48 with data processing and analysis performed using the QANT software package.52 GIWAXS GIWAXS measurements were performed at the SAXS/WAXS beamline of the Australian Synchrotron.53 Photon energy of either 9 keV or 11 keV was used with scattering recorded on a Dectris Pilatus 1M detector. Acquisition times of 1 s were used for 3 images with offset detector positions taken per sample that were then stitched in software to fill in the detector gaps. The sample-to-detector distance was calibrated using a silver behenate sample. The angle of incidence was set to 0 by determining the stage height and tilt so that 50% of the transmitted beam was cut by the sample, as recorded by a crystal analyzer. A full set of angle-dependent data was taken with data taken at the critical angle presented identified as the angle that gave the highest scattering



Page 22 of 27

intensity. Data was analyzed using a modified version of the Nika software package54 implemented in Igor Pro. ASSOCIATED CONTENT Supporting Information. Snthetic scheme, gel permeation chromatography, proton nuclear magnetic resonance, cyclovoltammetry, thermogravimetric analysis, differential scanning calorimeter, list of solvents used for calculating Hansen solubility parameter, Hansen parameter values, transfer characteristics and parameters of OFETs of IID24-CNTVT. Molecular structure, 3D-structure with dihedral angles and UV-vis absorption spectra of IID24-TVT, HOMO and LUMO energy levels by DFT calculation of IID24-CNTVT and IID24-TVT. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (Y.-Y. Noh). * E-mail:[email protected] (Y.-H. Kim).

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was supported by the Center for Advanced Soft-Electronics (2013M3A6A5073183 & 2013M3A6A5073172) funded by the Ministry of Science, ICT & Future Planning and the NRF


Page 23 of 27 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


grant funded by the Korea government (MSIP) (N2015R1A2A1A10055620). Part of this work was performed at the SAXS/WAXS and Soft X-ray beamlines at the Australian Synchrotron, Victoria, Australia. C.R.M. acknowledges support from the Australian Research Council (DP130102616). REFERENCES 1. Venkateshvaran, D.; Nikolka, M.; Sadhanala, A.; Lemaur, V.; Zelazny, M.; Kepa, M.; Hurhangee, M.; Kronemeijer, A. J.; Pecunia, V.; Nasrallah, I., Approaching disorder-free transport in high-mobility conjugated polymers. Nature 2014, 515 (7527), 384. 2. Biniek, L.; Schroeder, B. C.; Nielsen, C. B.; McCulloch, I., Recent advances in high mobility donor–acceptor semiconducting polymers. Journal of Materials Chemistry 2012, 22 (30), 14803-14813. 3. Khim, D.; Han, H.; Baeg, K. J.; Kim, J.; Kwak, S. W.; Kim, D. Y.; Noh, Y. Y., Simple Bar‐Coating Process for Large‐Area, High‐Performance Organic Field‐Effect Transistors and Ambipolar Complementary Integrated Circuits. Advanced Materials 2013, 25 (31), 4302-4308. 4. Li, J.; Zhao, Y.; Tan, H. S.; Guo, Y.; Di, C.-A.; Yu, G.; Liu, Y.; Lin, M.; Lim, S. H.; Zhou, Y., A stable solution-processed polymer semiconductor with record high-mobility for printed transistors. Scientific reports 2012, 2, 754. 5. Noriega, R.; Rivnay, J.; Vandewal, K.; Koch, F. P.; Stingelin, N.; Smith, P.; Toney, M. F.; Salleo, A., A general relationship between disorder, aggregation and charge transport in conjugated polymers. Nature materials 2013, 12 (11), 1038. 6. Søndergaard, R. R.; Hösel, M.; Krebs, F. C., Roll‐to‐Roll fabrication of large area functional organic materials. Journal of Polymer Science Part B: Polymer Physics 2013, 51 (1), 16-34. 7. Tsao, H. N.; Cho, D.; Andreasen, J. W.; Rouhanipour, A.; Breiby, D. W.; Pisula, W.; Müllen, K., The Influence of Morphology on High‐Performance Polymer Field‐Effect Transistors. Advanced Materials 2009, 21 (2), 209-212. 8. Zhang, X.; Bronstein, H.; Kronemeijer, A. J.; Smith, J.; Kim, Y.; Kline, R. J.; Richter, L. J.; Anthopoulos, T. D.; Sirringhaus, H.; Song, K., Molecular origin of high field-effect mobility in an indacenodithiophene–benzothiadiazole copolymer. Nature communications 2013, 4, 2238. 9. Brédas, J.-L.; Beljonne, D.; Coropceanu, V.; Cornil, J., Charge-transfer and energy-transfer processes in π-conjugated oligomers and polymers: a molecular picture. Chemical reviews 2004, 104 (11), 4971-5004. 10. Chen, F.-C.; Tsai, T.-H.; Chien, S.-C., Simple source/drain contact structure for solutionprocessed n-channel fullerene thin-film transistors. Organic Electronics 2012, 13 (4), 599-603. 11. Dey, A.; Kalita, A.; Krishnan Iyer, P., High-performance n-channel organic thin-film transistor based on naphthalene diimide. ACS applied materials & interfaces 2014, 6 (15), 1229512301. 12. Facchetti, A., π-Conjugated polymers for organic electronics and photovoltaic cell applications. Chemistry of Materials 2010, 23 (3), 733-758.



Page 24 of 27

13. Robin, M.; Harnois, M.; Molard, Y.; Jacques, E., Improvement of n-type OTFT electrical stability by gold electrode modification. Organic Electronics 2016, 39, 214-221. 14. Sokolov, A. N.; Atahan-Evrenk, S.; Mondal, R.; Akkerman, H. B.; Sánchez-Carrera, R. S.; Granados-Focil, S.; Schrier, J.; Mannsfeld, S. C.; Zoombelt, A. P.; Bao, Z., From computational discovery to experimental characterization of a high hole mobility organic crystal. Nature communications 2011, 2, 437. 15. Tseng, H. R.; Phan, H.; Luo, C.; Wang, M.; Perez, L. A.; Patel, S. N.; Ying, L.; Kramer, E. J.; Nguyen, T. Q.; Bazan, G. C., High‐Mobility Field‐Effect Transistors Fabricated with Macroscopic Aligned Semiconducting Polymers. Advanced Materials 2014, 26 (19), 2993-2998. 16. Yamashita, Y.; Hinkel, F.; Marszalek, T.; Zajaczkowski, W.; Pisula, W.; Baumgarten, M.; Matsui, H.; Müllen, K.; Takeya, J., Mobility Exceeding 10 cm2/(V· s) in Donor–Acceptor Polymer Transistors with Band-like Charge Transport. Chemistry of Materials 2016, 28 (2), 420-424. 17. Kajiya, D.; Ozawa, S.; Koganezawa, T.; Saitow, K.-i., Enhancement of out-of-plane mobility in P3HT film by rubbing: aggregation and planarity enhanced with low regioregularity. The Journal of Physical Chemistry C 2015, 119 (15), 7987-7995. 18. Pisula, W.; Menon, A.; Stepputat, M.; Lieberwirth, I.; Kolb, U.; Tracz, A.; Sirringhaus, H.; Pakula, T.; Müllen, K., A zone‐casting technique for device fabrication of field‐effect transistors based on discotic hexa‐peri‐hexabenzocoronene. Advanced Materials 2005, 17 (6), 684-689. 19. Ying, L.; Huang, F.; Bazan, G. C., Regioregular narrow-bandgap-conjugated polymers for plastic electronics. Nature communications 2017, 8, 14047. 20. Hu, H.; Zhao, K.; Fernandes, N.; Boufflet, P.; Bannock, J. H.; Yu, L.; de Mello, J. C.; Stingelin, N.; Heeney, M.; Giannelis, E. P., Entanglements in marginal solutions: a means of tuning pre-aggregation of conjugated polymers with positive implications for charge transport. Journal of Materials Chemistry C 2015, 3 (28), 7394-7404. 21. Luzio, A.; Criante, L.; D'innocenzo, V.; Caironi, M., Control of charge transport in a semiconducting copolymer by solvent-induced long-range order. Scientific reports 2013, 3, 3425. 22. Steyrleuthner, R.; Schubert, M.; Howard, I.; Klaumünzer, B.; Schilling, K.; Chen, Z.; Saalfrank, P.; Laquai, F. d. r.; Facchetti, A.; Neher, D., Aggregation in a high-mobility n-type lowbandgap copolymer with implications on semicrystalline morphology. Journal of the American Chemical Society 2012, 134 (44), 18303-18317. 23. Chen, H.; Guo, Y.; Yu, G.; Zhao, Y.; Zhang, J.; Gao, D.; Liu, H.; Liu, Y., Highly π‐ Extended Copolymers with Diketopyrrolopyrrole Moieties for High‐Performance Field‐Effect Transistors. Advanced Materials 2012, 24 (34), 4618-4622. 24. Lee, J.; Han, A.-R.; Yu, H.; Shin, T. J.; Yang, C.; Oh, J. H., Boosting the ambipolar performance of solution-processable polymer semiconductors via hybrid side-chain engineering. Journal of the American Chemical Society 2013, 135 (25), 9540-9547. 25. Bucella, S. G.; Luzio, A.; Gann, E.; Thomsen, L.; McNeill, C. R.; Pace, G.; Perinot, A.; Chen, Z.; Facchetti, A.; Caironi, M., Macroscopic and high-throughput printing of aligned nanostructured polymer semiconductors for MHz large-area electronics. Nature communications 2015, 6, 8394. 26. Matsidik, R.; Komber, H.; Luzio, A.; Caironi, M.; Sommer, M., Defect-free naphthalene diimide bithiophene copolymers with controlled molar mass and high performance via direct arylation polycondensation. Journal of the American Chemical Society 2015, 137 (20), 6705-6711. 27. Park, Y. D.; Lee, H. S.; Choi, Y. J.; Kwak, D.; Cho, J. H.; Lee, S.; Cho, K., Solubility‐ Induced Ordered Polythiophene Precursors for High‐Performance Organic Thin‐Film Transistors. Advanced Functional Materials 2009, 19 (8), 1200-1206.


Page 25 of 27 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


28. Van Tho, L.; Park, W.-T.; Choi, E.-Y.; Noh, Y.-Y., Highly aligned conjugated polymer films prepared by rotation coating for high-performance organic field-effect transistors. Applied Physics Letters 2017, 110 (16), 163303. 29. Tang, C.; Tracz, A.; Kruk, M.; Zhang, R.; Smilgies, D.-M.; Matyjaszewski, K.; Kowalewski, T., Long-range ordered thin films of block copolymers prepared by zone-casting and their thermal conversion into ordered nanostructured carbon. Journal of the American Chemical Society 2005, 127 (19), 6918-6919. 30. Tseng, H.-R.; Ying, L.; Hsu, B. B.; Perez, L. A.; Takacs, C. J.; Bazan, G. C.; Heeger, A. J., High mobility field effect transistors based on macroscopically oriented regioregular copolymers. Nano letters 2012, 12 (12), 6353-6357. 31. Yuan, Y.; Giri, G.; Ayzner, A. L.; Zoombelt, A. P.; Mannsfeld, S. C.; Chen, J.; Nordlund, D.; Toney, M. F.; Huang, J.; Bao, Z., Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method. Nature communications 2014, 5, 3005. 32. Cheon, K. H.; Ahn, H.; Cho, J.; Yun, H. J.; Lim, B. T.; Yun, D. J.; Lee, H. K.; Kwon, S. K.; Kim, Y. H.; Chung, D. S., Alcohol as a processing solvent of polymeric semiconductors to fabricate environmentally benign and high performance polymer field effect transistors. Advanced Functional Materials 2015, 25 (30), 4844-4850. 33. Cho, J.; Cheon, K. H.; Ahn, H.; Park, K. H.; Kwon, S. K.; Kim, Y. H.; Chung, D. S., High Charge‐Carrier Mobility of 2.5 cm2 V− 1 s− 1 from a Water‐Borne Colloid of a Polymeric Semiconductor via Smart Surfactant Engineering. Advanced Materials 2015, 27 (37), 5587-5592. 34. Kang, B.; Kim, R.; Lee, S. B.; Kwon, S.-K.; Kim, Y.-H.; Cho, K., Side-chain-induced rigid backbone organization of polymer semiconductors through semifluoroalkyl side chains. Journal of the American Chemical Society 2016, 138 (11), 3679-3686. 35. Kang, I.; An, T. K.; Hong, J.; Yun, H. J.; Kim, R.; Chung, D. S.; Park, C. E.; Kim, Y. H.; Kwon, S. K., Effect of Selenophene in a DPP Copolymer Incorporating a Vinyl Group for High‐ Performance Organic Field‐Effect Transistors. Advanced Materials 2013, 25 (4), 524-528. 36. Kang, I.; Yun, H.-J.; Chung, D. S.; Kwon, S.-K.; Kim, Y.-H., Record high hole mobility in polymer semiconductors via side-chain engineering. Journal of the American Chemical Society 2013, 135 (40), 14896-14899. 37. Lei, T.; Dou, J. H.; Pei, J., Influence of Alkyl Chain Branching Positions on the Hole Mobilities of Polymer Thin‐Film Transistors. Advanced Materials 2012, 24 (48), 6457-6461. 38. Sun, B.; Hong, W.; Aziz, H.; Li, Y., A pyridine-flanked diketopyrrolopyrrole (DPP)-based donor–acceptor polymer showing high mobility in ambipolar and n-channel organic thin film transistors. Polymer Chemistry 2015, 6 (6), 938-945. 39. Lei, T.; Wang, J.-Y.; Pei, J., Design, synthesis, and structure–property relationships of isoindigo-based conjugated polymers. Accounts of chemical research 2014, 47 (4), 1117-1126. 40. Park, K. H.; Cheon, K. H.; Lee, Y.-J.; Chung, D. S.; Kwon, S.-K.; Kim, Y.-H., Isoindigobased polymer field-effect transistors: effects of selenophene-substitution on high charge carrier mobility. Chemical Communications 2015, 51 (38), 8120-8122. 41. Yu, H.; Park, K. H.; Song, I.; Kim, M.-J.; Kim, Y.-H.; Oh, J. H., Effect of the alkyl spacer length on the electrical performance of diketopyrrolopyrrole-thiophene vinylene thiophene polymer semiconductors. Journal of Materials Chemistry C 2015, 3 (44), 11697-11704. 42. 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. Advanced Materials 2017, 29 (13).



Page 26 of 27

43. Yang, J.; Zhao, Z.; Geng, H.; Cheng, C.; Chen, J.; Sun, Y.; Shi, L.; Yi, Y.; Shuai, Z.; Guo, Y., Isoindigo‐Based Polymers with Small Effective Masses for High‐Mobility Ambipolar Field‐ Effect Transistors. Advanced Materials 2017, 29 (36). 44. Gaikwad, A. M.; Khan, Y.; Ostfeld, A. E.; Pandya, S.; Abraham, S.; Arias, A. C., Identifying orthogonal solvents for solution processed organic transistors. Organic Electronics 2016, 30, 18-29. 45. Hildebrand, J. H., An improvement in the theory of regular solutions. Proc Natl Acad Sci U S A 1979, 76 (12), 6040-1. 46. Chandler, D.; Weeks, J. D.; Andersen, H. C., Van der waals picture of liquids, solids, and phase transformations. Science 1983, 220 (4599), 787-94. 47. Opoku, H.; Nketia-Yawson, B.; Shin, E. S.; Noh, Y.-Y., Controlling organization of conjugated polymer films from binary solvent mixtures for high performance organic field-effect transistors. Organic Electronics 2017, 41, 198-204. 48. Nahid, M. M.; Gann, E.; Thomsen, L.; McNeill, C. R., NEXAFS spectroscopy of conjugated polymers. European Polymer Journal 2016, 81, 532-554. 49. Kim, N.-K.; Jang, S.-Y.; Pace, G.; Caironi, M.; Park, W.-T.; Khim, D.; Kim, J.; Kim, D.Y.; Noh, Y.-Y., High-performance organic field-effect transistors with directionally aligned conjugated polymer film deposited from pre-aggregated solution. Chemistry of Materials 2015, 27 (24), 8345-8353. 50. 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 Isoindigo‐Based Donor–Acceptor Conjugated Polymers. Advanced Functional Materials 2016, 26 (26), 4695-4703. 51. Cowie, B.; Tadich, A.; Thomsen, L. In The current performance of the wide range (90– 2500 eV) soft x‐ray beamline at the Australian Synchrotron, AIP Conference Proceedings, AIP: 2010; pp 307-310. 52. Gann, E.; McNeill, C. R.; Tadich, A.; Cowie, B. C.; Thomsen, L., Quick AS NEXAFS Tool (QANT): a program for NEXAFS loading and analysis developed at the Australian Synchrotron. Journal of synchrotron radiation 2016, 23 (1), 374-380. 53. Kirby, N. M.; Mudie, S. T.; Hawley, A. M.; Cookson, D. J.; Mertens, H. D.; Cowieson, N.; Samardzic-Boban, V., A low-background-intensity focusing small-angle X-ray scattering undulator beamline. Journal of Applied Crystallography 2013, 46 (6), 1670-1680. 54. Ilavsky, J., Nika: software for two-dimensional data reduction. Journal of Applied Crystallography 2012, 45 (2), 324-328.


Page 27 of 27 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


TOC


Design of New Isoindigo Based Copolymer for Ambipolar Organic

Recommend Documents