High-Performance Furan-Containing Conjugated Polymer for

Apr 21, 2017 - This mobility of 1.87 cm2 V–1 s–1 represents the highest performances among furan-containing polymers reported to the best of our k...
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A High-Performance Furan-Containing Conjugated Polymer for Environmentally Benign Solution Processing Sang Myeon Lee, Hae Rang Lee, A-Reum Han, Junghoon Lee, Joon Hak Oh, and Changduk Yang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 21 Apr 2017 Downloaded from http://pubs.acs.org on April 22, 2017

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A High-Performance Furan-Containing Conjugated Polymer for Environmentally Benign Solution Processing Sang Myeon Lee,†, § Hae Rang Lee,‡, § A-Reum Han, ‡ Junghoon Lee, † Joon Hak Oh, ‡,* and Changduk Yang†,* † Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 44919, South Korea ‡ Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk 37673, South Korea § These authors contributed equally to this work.

Keywords: diketopyrrolopyrrole, furan-containing conjugated polymers, siloxane-hybrid chains, organic field-effect transistors, non-chlorinated solvents

Abstract

Developing semiconducting polymers that exhibit both strong charge transport capability via highly ordered structures and good processability in environmentally benign solvents remains 1 ACS Paragon Plus Environment

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a challenge. Given that furan-based materials have better solubility in various solvents than analogous thiophene-based materials, we have synthesized and characterized furanyldiketopyrrolopyrrole polymer (PFDPPTT-Si) together with its thienyl-diketopyrrolopyrrolebased analogue (PTDPPTT-Si) to understand subtle changes induced by the use of furan instead of thiophene units. PTDPPTT-Si films processed in common chlorinated solvent exhibit a higher hole mobility (3.57 cm2 V−1 s−1) than PFDPPTT-Si films (2.40 cm2 V−1 s−1) under the same conditions; this greater hole mobility is a result of tightly aggregated πstacking structures in PTDPPTT-Si. By contrast, because of its enhanced solubility, PFDPPTT-Si using chlorine-free solution processing results in a device with higher mobility (as high as 1.87 cm2 V−1 s−1) compared to that of the corresponding device fabricated using PTDPPTT-Si. This mobility of 1.87 cm2 V−1 s−1 represents the highest performances among furan-containing polymers reported to the best of our knowledge for non-chlorinated solvents. Our study demonstrates an important step toward environmentally compatible electronics, and we expect the results of our study to reinvigorate the furan-containing semiconductors field.

1. Introduction A central approach in the synthesis of materials for organic field-effect transistors (OFETs) is to manipulate electron donor (D) and acceptor (A) blocks in π-conjugated semiconducting polymers to achieve controllable energy band gaps and tunable charge transport properties in the conjugation systems.1-5 Among such alternating D–A polymers, diketopyrrolopyrrole (DPP)-containing polymers exhibit dense π–π stacking and long-range order because of the coplanar nature of a DPP moiety with less conformational disorder, and a high charge transport capability; DPP-based polymers have thus led to rapid progress in the development of high-performance OFETs.6-10 2 ACS Paragon Plus Environment

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Despite DPP-containing polymers’ beneficial characteristics for use in electronics, their rigid DPP skeleton leads to poor solubility in various commercial solvents, except chlorinecontaining solvents. Thus, the use of such chlorinated solvents is a prerequisite to realizing high-performance OFETs based on DPP polymers.11-15 However, chlorinated solvents are well-known for energy-intensive chemicals that harm the environment,16-18 which pose a substantial obstacle to the manufacture of electronic devices beyond the laboratory scale.19-22 Driven by the urgent demand for high performing DPP-based materials with good solubility for solving aggregating properties to some extent, considerable attention has been devoted to introducing long or bulky solubilizing chains into the main backbones;13, 23-26 however, the resultant polymers form less-crystalline structures in the films, and these structures adversely affect charge mobility in OFETs. In addition to the side-chain engineering, irregular synthetic approaches (e.g., random polymerization27-28 and structural asymmetry29-30) in DPP-based polymers have beneficial microstructures with good solubility/processability; enabling excellent performance of OFETs fabricated using DPP-containing polymers in non-chlorinated solvents. Nonetheless, variations in the composition of random DPP polymers with a lower molecular precision can result in batch-to-batch errors for the processing properties and performance.31-33 In addition, incorporating two different aromatic substituents for the asymmetric DPP polymers is complex. Furan-containing polymers have been found to not only exhibit greater solubility in common solvents than the thiophene analogues but also comparable performance in electronic applications.34-38 This interest in furan-based materials potentially useful for green electronics has recently expedited the development of OFETs of furanyl-DPP (FDPP)-based polymers39-45 using non-chlorinated solution processing;46 however, the mobilities of the

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FDPP-based polymers remains no greater than 0.26 cm2 V-1 s-1, which is substantially lower than the analogous thienyl-DPP (TDPP)-based materials. In the work described herein, our growing interest in the development of highperforming OFETs fabricated using an environmentally friendly process prompted us to explore the OFET properties of a new FDPP-based polymer, where the FDPP with siloxaneside chains was polymerized with a thieno[3,2-b]thiophene (TT) to generate PFDPPTT-Si. To systematically investigate the heterocyclic change, we also synthesized and characterized the corresponding thiophene analogue PTDPPTT-Si. The high hole mobilities of PTDPPTTSi and PFDPPTT-Si cast from CF were 3.57 and 2.40 cm2 V−1 s−1, respectively. Importantly, PFDPPTT-Si exhibits better solubility in various non-chlorinated solvents, which can minimize detrimental changes in morphology in non-chlorinated processing solvents, thereby providing a higher mobility of 1.33-1.87 cm2 V−1 s−1 in the films processed from environmentally benign solvents compared with the mobilities in the PTDPPTT-Si devices. Our measured values of PFDPPTT-Si, in the case of samples cast using chlorine-free solvents, is the highest mobilities reported to date for benign furan-containing-polymer-based OFETs, indicating that PFDPPTT-Si as a promising candidate for environmentally compatible OFETs.

2. Results and Discussion 2.1. Synthesis and Characterization The synthesis procedures for the two polymers, PTDPPTT-Si and PFDPPTT-Si, are shown in Scheme 1. We previously demonstrated that the use of siloxane-terminated pentyl chains in DPP-based polymers can impart sufficient solubility and excellent charge-carrier mobility.15, 23, 47 Therefore, we chose siloxane-terminated pentyl chains as solubilizing groups in this study. First, 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione and 3,6di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione were synthesized according to the 4 ACS Paragon Plus Environment

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reported procedures.40, 48 Each of the dibrominated TDPP and FDPP monomers was achieved via successive three-step reactions (i.e., alkylation, hydrosilylation, and bromination). The detailed synthetic procedures with the characterization data are described in the Supporting Information. Finally, PTDPPTT-Si and PFDPPTT-Si were prepared via Stille coupling polymerization of their dibrominated monomers with the bis-stannylated TT co-monomer. Soxhlet extraction with methanol, acetone, and hexane sequentially was carried out to remove the catalytic residues and oligomer mixtures in both polymers. The gel permeation chromatography (GPC) at room temperature in tetrahydrofuran shows similarly high numberaverage molecular weights (Mn) of PTDPPTT-Si (55.4 kDa) and PFDPPTT-Si (47.2 kDa) with a relatively broad range of polydispersity indices (PDIs). This step can minimize possible interference from Mn variations.

Scheme 1. Molecular structures of PTDPPTT-Si and PFDPPTT-Si with the synthetic routes. i) 5-Bromo-1-pentene, K2CO3, DMF, 120

o

C, overnight, 81%; ii) 1,1,1,3,5,5,5-

Heptamethyltrisiloxane, Karstedt’s catalyst, toluene, reflux, overnight, 79%; iii) NBS, CHCl3, r.t. in dark, 1 hr, 88%; iv) Pd2(dba)3, P(o-tolyl)3, toluene, 100 oC, 12 hrs, 79% and 82%, respectively.

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Si

Si O

O

Si

Si O

O

O NH

O N

i)

O O

N

ii)

O

O N O Br

O

HN

N O

N

Si

O

1

N O

O

2

Si

O Si

X

Br

+

N

iv)

S Me3Sn

N R

R

O X

Br

Si

R N

X

SnMe3

Si Si

O

S

N R

R:

S

X

S

O

Si O

3

Si

O

O

Br

O

Si

O

O

Si

iii)

O

O

O

Si

n

O

X = S, PTDPPTT-Si X = O, PFDPPTT-Si

2.2. Optical and Electrochemical Properties and Theoretical Calculations The optical properties with UV-vis absorption spectra of solution in chloroform and thin films of both polymers are displayed in Figure 1; the relevant data are summarized in Table 1. Both polymers showed similarly broad absorptions from 350 nm to 950 nm. The π-π* transition band and intramolecular charge transfer (ICT) between the A and D moieties are exhibited as shorter- and longer-wavelength peaks, respectively. The absorption profiles of PTDPPTT-Si both in solution and as films are much broader than those of PFDPPTT-Si, confirming the stronger interchain aggregation of PTDPPTT-Si. Notably, a blue shift of the absorption features from PTDPPTT-Si to PFDPPTT-Si in both solution and films was observed, indicating that the PFDPPTT-Si polymer chains were less aggregated because of the smaller heteroatoms of the furan unit.49-51 Consequently, the optical band gap (Eg) as estimated from the absorption onset (1.31 eV) of the PTDPPTT-Si film, was smaller than that of PFDPPTT-Si (1.39 eV).

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Figure 1. Normalized UV-Vis absorption profiles in chloroform solution (a) and as thin films (b), UV photoelectron spectroscopy (UPS) spectra (c) and energy level diagram (d) of PTDPPTT-Si and PFDPPTT-Si. UV photoelectron spectroscopy (UPS) was carried out for the highest occupied molecular orbital (HOMO) energy levels of the two polymers and the lowest unoccupied molecular orbital (LUMO) energy levels were found on the basis of the Eg in the absorption spectra and the HOMO energy levels. The HOMO values of PTDPPTT-Si and PFDPPTT-Si as-spun films were -4.67 and -4.71 eV, as shown in Figure 1d. These values are slightly higher than those measured by cyclic voltammetry (Figure S1 and Table S1), although the same variation trends are observed. The calculated LUMO values are -3.36 and -3.32 eV for PTDPPTT-Si and PFDPPTT-Si, respectively. Notably, the HOMO level of PFDPPTT-Si is 7 ACS Paragon Plus Environment

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slightly deeper than that of PTDPPTT-Si because of the relatively high ionization potential of furan.52

Table 1. Optical and electronic properties of the PDPPTT-Si polymers λmaxsol

λmaxfilm

Eg

EHOMO

ELUMO

(nm)a

(nm)

(eV)b

(eV)c

(eV)d

PTDPPTT-Si

745, 807

739, 810

1.31

-4.67

-3.36

PFDPPTT-Si

797

724, 800

1.39

-4.71

-3.32

Polymer

a

Polymer solutions in chloroform and films on glass substrates; bdetermined from the onset of the UV-vis absorption plots in the polymer films; cmeasured by UPS measurements, incident photon energy (hν = 21.2 eV) for He I (EHOMOUPS = hν - (Ecutoff - EHOMO); dELUMO = EHOMO Eg. Furthermore, the density functional theory (DFT) method at the B3LYP/6-31G* level calculated the electron distributions of HOMO and LUMO in the single repeating units for the two polymers (Figure S2). The both models showed well-delocalized electron densities over the conjugated backbones for both the HOMO and the LUMO.

2.3. Thin-Film Microstructure Analysis The film morphological features of PTDPPTT-Si and PFDPPTT-Si were investigated using tapping-mode atomic force microscopy (AFM). As shown in Figure 2, both as-cast and annealed polymer films exhibited densely packed nanofibrillar networks, indicating the existence of strong intermolecular interactions13 and the formation of highly interconnected charge transport pathways. Moreover, the thermal annealing at 260 °C caused the nanofibrous features to become more evident, with a slight increase of the root-mean-square (RMS) roughness from 1.99 to 2.65 nm for PTDPPTT-Si and from 0.96 to 1.46 nm for PFDPPTT-Si; this increased roughness suggests that the crrystalline nanostructures were 8 ACS Paragon Plus Environment

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improved after thermal annealing.4, 53, 54 We note that the annealed PTDPPTT-Si film exhibited larger fibrous crystalline domains with an average diameter of ~56 nm which indicates much less grain-boundary formation compared to those observed in PFDPPTT-Si films (~27 nm of average diameter). Based on the aforementioned UV-vis absorption spectra and AFM result, we could easily conclude that the molecular structure of PTDPPTT-Si is beneficial to form stronger aggregation.

(a)

13 nm

10 nm

18 nm

10 nm

RRMS=1.99 nm

RRMS=0.96 nm

RRMS=2.65 nm

RRMS=1.46 nm

18 °

(b)

(c)

12 °

(d)

20 °

10 °

Figure 2. AFM height (top) and phase (bottom) images of CF-solution-processed PDPPTTSi films (a,b) before and (c,d) after thermal treatment. (a,c) PTDPPTT-Si and (b,d) PFDPPTT-Si were fabricated on OTS-treated SiO2/Si substrates. Scale bar = 400 nm.

Grazing-incidence X-ray diffraction (GIXD) analyses were conducted to clarify the crystallinities and molecular-packing orientations of the PDPPTT-Si polymers. Twodimensional (2D) detector images are provided with their horizontal and vertical line cuts of 9 ACS Paragon Plus Environment

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annealed polymer films in Figure 3 (see Figure S3 for those of the as-cast films). The corresponding crystallographic parameters are shown in Table S2. Both of the as-cast films exhibited highly ordered structures with out-of-plane (100) layer distances of 21.91 and 20.90 Å for the PTDPPTT-Si and PFDPPTT-Si films, respectively; these distances are corresponding to the lamellar distances between two backbones which is determined by the length of the lateral side chains. After the films were annealed at 260 °C, the diffraction images exhibited slightly intensified peaks and decreased (100) d-spacing values of 21.61 and 20.88 Å for PTDPPTT-Si and PFDPPTT-Si films, respectively, which implies that thermal annealing induced side chains of adjacent backbones to closely interdigitate.55 However, in the case of both polymers, the observation of (010) π−π stacking peaks along both qxy and qz directions indicates bimodal packing with coexisting edge-on and face-on orientations. PTDPPTT-Si films exhibited stronger (010) diffraction peaks with denser (spacing of ~3.65 Å) π−π stacking than those of PFDPPTT-Si films (~3.74 Å), indicating that the thiophene spacer facilitates microstructures that favor charge transport with stronger intermolecular interactions in PTDPPTT-Si. In principle, these stronger π−π interactions are due to the nature of sulfur in thiophene with greater overlap integrals and polarizabilities with enhanced aromaticity compared to that of oxygen in furan units.56,57 Yet, simultaneously, this observation leads us to expect an adverse effect on the solubility of PTDPPTT-Si in various common solvents. Overall, the aforementioned AFM and GIXD data establish an important trend in the film morphology with respect to thiophene versus furan.

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PTDPPTT-Si

(010)

qz (Å-1)

1.5

(300) (200)

0.5

(100)

-1.5

-1.0

-0.5

0.0

0.5

1.0

0.0

1.5

(010)

0.5

1.0

1.5

(300) (200)

0.5

(d)

Intensity (a.u.)

(c)

(010)

(100)

(010)

1.0

PFDPPTT-Si

-1.5

-1.0

-0.5

0.0

0.5

qxy (Å-1)

(010)

1.0

1.5

ii SS -TT TT PP PP DD TF PP

qxy (Å-1)

2.0 1.5

(400)

1.0

0.0

(b)

Intensity (a.u.)

2.0

qz (Å-1)

(a)

ii SS -TT TT PP PP DD TF PP

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(100)

(200)

(300) (400)

0.5

-1

q xy ( Å )

1.0

(010)

1.5

2.0

-1

qz (Å )

Figure 3. 2D-GIXD images of CF-solution-processed (a) PTDPPTT-Si and (b) PFDPPTT-Si films, and their line cut profiles through of (c) horizontal (qxy) and (d) vertical (qz) directions. The PDPPTT-Si films were formed on OTS-treated SiO2/Si substrates and annealed at 260 oC.

2.4. Electrical Characterization and the Performance of OFETs To investigate the electrical properties of PTDPPTT-Si and PFDPPTT-Si, we first fabricated bottom-gate top-contact CF-cast OFET devices, as depicted in Figure 4a, and measured their charge transport characteristics under a nitrogen atmosphere. The detailed OFET fabrication and characterization steps are provided in the Experimental section. Both polymers exhibited unipolar p-type field-effect behaviors because of the lower energetic barriers with regard to the gold electrode contacts. The solution-sheared films were thermally annealed at various temperatures (220, 260, and 300 °C) to investigate the optimal posttreatment conditions (Figures 4b, Figure S4 and Table 2). The as-cast polymer films 11 ACS Paragon Plus Environment

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exhibited hole mobilities of 1.20 and 0.43 cm2 V−1 s−1 for PTDPPTT-Si and PFDPPTT-Si, respectively. Thermal annealing was found to further enhance the electrical properties, and the optimal annealing temperature was 260 °C.

PTDPPTT-Si

10-4

30 10

Polymer thin-film OTSSAM layer

(b)

-4

10-5 10

-6

10

-7

0

PTDPPTT-Si

(d)10

-3

10

-4

10

-5

2

-6

10

-7

10-8

-80V

0.2 -60V

0.1

-40V

10-9

0 -100

10

-10

10

-11

-20V

0.0

0

0 0 220 260 300

Ta ( C) o

10-3

25

10-4

15 -6

10

-7

10

-8

10

-9

(h)

10 5

0

-50

-100

PFDPPTT-Si 0.2 VGS= -100V -80V

10-5

0 -100

VGS (V)

10

-6

10-7 10-8

lIGSl (A)

PFDPPTT-Si

PFDPPTT-Si

20

10

-50

VDS (V)

(-ID)1/2 (mA1/2)

1

-IDS (A)

-1

-50

10

VGS= -100V

VGS (V)

3

-1 2

10

10-8

4

µh (cm V s )

20

10

-5

lIGSl (A)

-IDS (A)

50 µm

0.3

-IDS (mA)

(a)

PTDPPTT-Si

10-3

-3

-IDS (mA)

(c) 10

(-ID)1/2 (mA1/2)

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

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-60V

0.1 -40V

10-9 10

-10

10

-11

-20V

0.0

0

-50

-100

VDS (V)

Figure 4. Schematic illustration of CF-processed PDPPTT-Si OFETs and their optimal electrical characteristics after thermal annealing treatment. (a) Device Structure of the fabricated OFET structure with Au electrodes of L= 50 µm and W= 1000 µm. (b) Comparison of the average hole mobilities of PDPPTT-Si films with various annealing temperature from up to 300 oC. Transfer and output curves of the optimized devices of (c) PTDPPTT-Si and (d) PFDPPTT-Si after annealing at 260 oC.

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Table 2. OFET performance of CF-solution-processed PDPPTT-Si filmsa

Polymer

PTDPPTT-Si

PFDPPTT-Si

µh,maxb

Ta

µh,avgc

VT Ion/Ioff

[oC]

[cm2 V-1 s-1]

[cm2 V-1 s-1]

N/Ad

1.20

0.98 (±0.12)e

>104

-13.1

220

1.93

1.41 (±0.26)

>104

-9.8

260

3.57

2.75 (±0.36)

>105

-15.9

300

2.56

2.20 (±0.22)

>105

-13.2

N/A

0.43

0.36 (±0.05)

>103

-14.0

220

1.35

0.94 (±0.20)

>104

-21.6

260

2.40

1.87 (±0.24)

>105

-16.7

300

1.44

1.15 (±0.12)

>104

-23.5

[V]

a

The OFET performance of more than 20 devices with various thermal annealing conditions was tested. bThe maximum and caverage mobility of the OFET devices (L = 50 µm and W = 1000 µm). dThermal annealing was not applied. eThe standard deviation. In addition, we compared the charge transport characteristics of drop-cast and solutionsheared films annealed at 260 °C. As shown in Figures 4c-d, solution-sheared PTDPPTT-Si and PFDPPTT-Si films showed hole mobilities as high as 3.57 and 2.40 cm2 V−1 s−1, respectively, whereas drop-cast films exhibited relatively lower electrical performances (hole mobilities of 2.70 and 2.01 cm2 V−1 s−1 for PTDPPTT-Si and PFDPPTT-Si, respectively) (Figure S5, Table S3). This result is closely related to the positive effects of solution-shearing, such as an elongated crystallite texture along the conducting channel and a well-organized polymer chain packing with a reduced π-planar distance.58,59 The OFETs with thiophene spacers exhibited better performance than the OFETs fabricated using furan spacers owing to the optimized microstructures with stronger intermolecular interactions. It’s because of the enhanced aromaticity of the thiophene unit in PTDPPTT-Si efficiently facilitated denser πstacking, as observed by AFM and GIXD and various analyses, revealing that morphological 13 ACS Paragon Plus Environment

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factors more critically affect charge transport compared to energetic factors in these polymer films.

2.5. Solubility Characteristics Before starting our work on chlorine-free OFETs as a main topic in this study, we carried out solubility tests of the two polymers in common non-chlorinated solvents—toluene (Tol), tetrahydrofuran (THF), o-xylene (Xyl), and 1,4-dioxane (Diox)—to measure the quantitative solubilities by UV-vis absorption (Figure S6 and Table S4) and confirm their solution processability (Figure 5a). PFDPPTT-Si exhibited better solubility at room temperature in the tested solvents because of the large dipole moment of PFDPPTT-Si; by contrast, PTDPPTT-Si exhibited sufficient solubility in THF and Tol only when heated at ~60 °C. To estimate accurate solubility boundaries for both polymers, we adopted Hansen solubility theory, which considers the energy from dispersion (δD), the dipolar intermolecular (δP), and the hydrogen bonding (δH) forces between molecules as constitutive interaction parameters.60 Figure 5b is a plot of the comprehensive solubility parameters of the tested solvents calculated from the equation (δD2 + δP2 + δH2)0.5. In addition, the detailed constitutive parameters and two-dimensional (2D) representation of δD and δP are depicted in Figures 5c and d, where we excluded the effect of δH because both polymers are lack of probability to form hydrogen bonding with used solvents. PFDPPTT-Si exhibited an enhanced solubility range with a larger radius of sphere in 2D Hansen space compared to PTDPPTT-Si.

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Figure 5. (a) Solubility test of PTDPPTT-Si (left in each pair of vials) and PFDPPTT-Si (right) in toluene, tetrahydrofuran, o-xylene, and 1,4-dioxane, respectively. (b-d) Summary of solubility test for various solvents represented using Hansen theory: (b) Comprehensive solubility data of both polymers. (c) Three-dimensional representation of Hansen solubility parameters. (d) Two-dimensional Hansen plot for δD versus δP.

To confirm the effect of solubility, we also investigated the morphologies and electrical characteristics of the polymer films using Tol and THF solutions, respectively (Figure 6). In the case of PTDPPTT-Si, a partially agglomerated morphology was obtained from the Tol solution because of the greater immiscibility between the polymer and the solvent, whereas critical morphology changes were not observed from PFDPPTT-Si when the processing solvents were varied. Furthermore, PFDPPTT-Si exhibited comparable electrical properties up to 1.87 cm2 V−1 s−1 with PTDPPTT-Si (maximum hole mobility ~ 1.82 cm2 V−1 s−1) when processed with Tol (Table 3). The hole mobilities in THF-processed samples were lower than those in Tol-processed samples. This result might originate from the lower boiling point 15 ACS Paragon Plus Environment

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(66 °C) of THF compared to that of Tol (111 °C), which reduces the time for crystallization during solution processing. With THF solution, intriguingly, PFDPPTT-Si maintained 41.7 % of CF-cast property whereas PTDPPTT-Si exhibited dramatic decrement in mobility up to 20 %, which indicates PFDPPTT-Si exhibited lower dependency of solvent type (Figure S7). PFDPPTT-Si is observed to be much more suitable for commercial use because of its greater solubility in various solvents, including environmentally benign solvents, and its better solvent-independent characteristics. To the extent of our knowledge, the mobilities of PFDPPTT-Si prepared with non-chlorinated solvents are the highest performance reported so far for furan-based polymers.

10

-9

-7

10

-8

10

-9

15 10

10

-1 0

5

10

-10

10

-1 1

0 -100

10

-11

0

-50

V G S (V )

20 15 10

1/2

-8

10

CF Tol TH F

(mA )

10

10

20

PFDPPTT-Si 25

V D S = -100V

1/2

10

-7

-6

1/2

-6

10

-5

25

(mA )

10

30

10

-4

5

(c)

PTDPPTT-Si PFDPPTT-Si

3.0 2.5

-1

-5

-3

15 nm

PFDPPTT-Si (THF)

-1

10

10

(-ID)

10

-4

PTDPPTT-Si 35

V D S = -100V

40 nm

PFDPPTT-Si (Tol)

2.0

2

-3

1/2

-ID (A)

10

20 nm

PTDPPTT-Si (THF)

-ID (A)

(b)

50 nm

µh (cm V s )

(a) PTDPPTT-Si (Tol)

(-ID)

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1.5 1.0 0.5

0

-50

0 -100

V G S (V )

1 CF

2 Tol

THF 3

Solvent

Figure 6. (a) AFM images of PDPPTT-Si films fabricated with toluene and tetrahydrofuran solutions. (b) Transunderminefer curves for comparative study of solvents and (c) corresponding average hole mobilities of PDPPTT-Si based OFETs.

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Table 3. OFET performance of PDPPTT-Si films processed with environmentally benign solvents

Polymer PTDPPTT-Si PFDPPTT-Si

Solvent Toluene Tetrahydrofuran Toluene Tetrahydrofuran

µh,max [cm2 V-1 s-1] 1.82 0.97 1.87 1.33

µh,avg [cm2 V-1 s-1] 1.54 (±0.15) 0.55 (±0.14) 1.55 (±0.18) 0.80 (±0.22)

Ion/Ioff >105 >106 >105 >106

VT [V] -28.2 -26.5 -28.6 -22.6

3. Conclusion Following recent broad interest in environmentally compatible electronic devices, we carried out a comprehensive investigation of two DPP-based polymers (PTDPPTT-Si and PFDPPTT-Si). The inherent differences between flanking thiophene and furan units in the backbones influenced the optoelectronic properties of the resulting polymers. For example, as a result of the smaller atomic radius and larger dipole moment of oxygen in the furan units, PFDPPTT-Si not only has a deeper-lying HOMO level with a slightly larger optical band gap but also greater solubility in non-chlorinated solvents compared to PTDPPTT-Si. The CF-cast OFETs of PTDPPTT-Si exhibited a greater mobility (3.57 cm2 V−1 s−1) as compared with that of PFDPPTT-Si (2.40 cm2 V−1 s−1) because of the stronger aggregation behavior in PTDPPTT-Si; conversely, the OFETs fabricated using in PFDPPTT-Si processed in nonchlorinated solvents delivered better mobility, 1.87 cm2 V−1 s−1. This mobility value is the highest reported thus far for “green” OFETs fabricated using furan-based polymers, demonstrating the strong potential for developing high-performance environmentally friendly organic semiconductors via incorporation of furan into polymer backbones.

4. Experimental Section 17 ACS Paragon Plus Environment

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4.1 Instruments for Characterizations Cary 5000 spectrophotometer, VersaSTAT3 Princeton Applied Research Potentiostat,62 and MultiMode 8 scanning probe microscope were used to obtain the UV-vis-NIR spectra, CV plots, and tapping-mode AFM images according to the reported methods. GPC was carried out through Agilent 1200 HPLC and miniDawn TREOS63 and DFT calculations were obtained with Gaussian 09 package.64 GIXD measurements were performed at PLS-II 9A USAXS beamline of Pohang Accelerator Laboratory in Korea, with the experimental details shown in our previous papers.13,15,65 Performances of fabricated OFETs were tested using a Keithley 4200 semiconductor parametric analyzer as reported previously.13,66 The specific conditions for GIXD measurements and OFETs fabrication were provided in the Supporting Information.

4.2 Solubility Measurement The solubilities of PTDPPTT-Si and PFDPPTT-Si were determined in the test solvents. For calibration, absorption spectra of both polymers were obtained with different concentrations in chloroform, in which the absorbance values at 807 nm for PTDPPTT-Si and at 797 nm for PFDPPTT-Si were varied linearly on the concentrations. Then, the saturated solutions of two polymers filtered for removal of an excess of solids in each test solvent, were diluted with additional solvent to lower the absorbance, followed by measuring UV absorptions. On a basis of Beer-Lambert’s law, the quantitative data were collected from a linear relationship of concentration with absorbance. In case of 1,4-dioxane as a solvent, the solubilities for both polymers were too low to take the reliable spectra in UV-vis absorption.

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ASSOCIATED CONTENT Supporting Information. Experimental details; CV plots; DFT calculations; GIXD data with the crystallographic parameters; transfer characteristics; solubility measurements with UV-vis spectra of PTDPPTT-Si and PFDPPTT-Si. This material is available free of charge on the ACS Publications website at DOI: xx.xxxx /acsami.xxxxxxx.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] * E-mail: [email protected]

ACKNOWLEDGMENTS S. M. L. and H. R. L. contributed equally. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (2015R1A2A1A10053397) and the Center for Advanced Soft-Electronics funded by the Ministry of Science, ICT and Future Planning as Global Frontier Project (CASE2013M3A6A5073175).

References (1)

Dong, H.; Fu, X.; Liu, J.; Wang, Z.; Hu, W. 25th Anniversary Article: Key Points for

High-Mobility Organic Field-Effect Transistors. Adv. Mater. 2013, 25, 6158-6183. 19 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

(2)

Page 20 of 30

Heeger, A. J. Semiconducting polymers: the Third Generation. Chem. Soc. Rev.

2010, 39, 2354-2371. (3)

Holliday, S.; Donaghey, J. E.; McCulloch, I. Advances in Charge Carrier Mobilities

of Semiconducting Polymers Used in Organic Transistors. Chem. Mater. 2014, 26, 647-663. (4)

Kim, G.; Kim, H.; Jang, M.; Jung, Y. K.; Oh, J. H.; Yang, C. Ultra-narrow-bandgap

Thienoisoindigo Polymers: Structure-Property Correlations in Field-Effect Transistors. J. Mater. Chem. C 2016, 4, 9554-9560. (5)

Tsao, H. N.; Cho, D. M.; Park, I.; Hansen, M. R.; Mavrinskiy, A.; Yoon, D. Y.; Graf,

R.; Pisula, W.; Spiess, H. W.; Müllen, K. Ultrahigh Mobility in Polymer Field-Effect Transistors by Design. J. Am. Chem. Soc. 2011, 133, 2605-2612. (6)

Bijleveld, J. C.; Zoombelt, A. P.; Mathijssen, S. G. J.; Wienk, M. M.; Turbiez, M.; de

Leeuw, D. M.; Janssen, R. A. J. Poly(diketopyrrolopyrrole−terthiophene) for Ambipolar Logic and Photovoltaics. J. Am. Chem. Soc. 2009, 131, 16616-16617. (7)

Gsänger, M.; Bialas, D.; Huang, L.; Stolte, M.; Würthner, F. Organic

Semiconductors based on Dyes and Color Pigments. Adv. Mater. 2016, 28, 3615-3645. (8)

Li, Y.; Sonar, P.; Murphy, L.; Hong, W. High Mobility Diketopyrrolopyrrole (DPP)-

based Organic Semiconductor Materials for Organic Thin Film Transistors and Photovoltaics. Energy Environ. Sci. 2013, 6, 1684-1710. (9)

Nielsen, C. B.; Turbiez, M.; McCulloch, I. Recent Advances in the Development of

Semiconducting DPP-Containing Polymers for Transistor Applications. Adv. Mater. 2013, 25, 1859-1880.

20 ACS Paragon Plus Environment

Page 21 of 30

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

(10) Yi, Z.; Wang, S.; Liu, Y. Design of High-Mobility Diketopyrrolopyrrole-Based πConjugated Copolymers for Organic Thin-Film Transistors. Adv. Mater. 2015, 27, 35893606. (11) Chen, Z.; Lee, M. J.; Shahid Ashraf, R.; Gu, Y.; Albert-Seifried, S.; Meedom Nielsen, M.; Schroeder, B.; Anthopoulos, T. D.; Heeney, M.; McCulloch, I.; Sirringhaus, H. High-Performance Ambipolar Diketopyrrolopyrrole-Thieno[3,2-b]thiophene Copolymer Field-Effect Transistors with Balanced Hole and Electron Mobilities. Adv. Mater. 2012, 24, 647-652. (12) Gao, Y.; Zhang, X.; Tian, H.; Zhang, J.; Yan, D.; Geng, Y.; Wang, F. High Mobility Ambipolar Diketopyrrolopyrrole-Based Conjugated Polymer Synthesized Via Direct Arylation Polycondensation. Adv. Mater. 2015, 27, 6753-6759. (13) Han, A.-R.; Dutta, G. K.; Lee, J.; Lee, H. R.; Lee, S. M.; Ahn, H.; Shin, T. J.; Oh, J. H.; Yang, C. ε-Branched Flexible Side Chain Substituted Diketopyrrolopyrrole-Containing Polymers Designed for High Hole and Electron Mobilities. Adv. Funct. Mater. 2015, 25, 247254. (14) 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. J. Am. Chem. Soc. 2013, 135, 14896-14899. (15) 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. J. Am. Chem. Soc. 2013, 135, 9540-9547. (16) Calamari D.; Galassi S.; Setti F.; Vighi M. Toxicity of Selected Chlorobenzenes to Aquatic Organisms. Chemosphere 1983, 12, 253-262. 21 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 22 of 30

(17) Van Gestel, C. A. M.; W. Ma.; Smit, C. E. Development of QSARs in Terrestrial Ecotoxicology: Earthworm Toxicity and Soil Sorption of Chlorophenols, Chlorobenzenes and Dichloroaniline. Sci. Total Environ. 1991, 109-110, 589-604. (18) Van Hoogen, G.; Opperhuizen, A. Toxicokinetics of Chlorobenzenes in Fish. Environ. Toxicol. Chem. 1988, 7, 213-219. (19) Chen, X.; Liu, X.; Burgers, M. A.; Huang, Y.; Bazan, G. C. Green-Solvent-Processed Molecular Solar Cells. Angew. Chem. Int. Ed. 2014, 53, 14378-14381. (20) Duan, C.; Cai, W.; Hsu, B. B. Y.; Zhong, C.; Zhang, K.; Liu, C.; Hu, Z.; Huang, F.; Bazan, G. C.; Heeger, A. J.; Cao, Y. Toward Green Solvent Processable Photovoltaic Materials for Polymer Solar Cells: The Role of Highly Polar Pendant Groups in Charge Carrier Transport and Photovoltaic Behavior. Energy Environ. Sci. 2013, 6, 3022-3034. (21) Farahat, M. E.; Tsao, C.-S.; Huang, Y.-C.; Chang, S. H.; Budiawan, W.; Wu, C.-G.; Chu, C.-W. Toward Environmentally Compatible Molecular Solar Cells Processed from Halogen-Free Solvents. J. Mater. Chem. A 2016, 4, 7341-7351. (22) Zhu, Y.; Chen, Z.; Yang, Y.; Cai, P.; Chen, J.; Li, Y.; Yang, W.; Peng, J.; Cao, Y. Using d-limonene as the Non-Aromatic and Non-Chlorinated Solvent for the Fabrications of High Performance Polymer Light-Emitting Diodes and Field-Effect Transistors. Org. Electron. 2015, 23, 193-198. (23) Han, A. R.; Lee, J.; Lee, H. R.; Lee, J.; Kang, S.-H.; Ahn, H.; Shin, T. J.; Oh, J. H.; Yang, C. Siloxane Side Chains: A Universal Tool for Practical Applications of Organic Field-Effect Transistors. Macromolecules 2016, 49, 3739-3748.

22 ACS Paragon Plus Environment

Page 23 of 30

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

(24) Li, W.; Hendriks, K. H.; Furlan, A.; Roelofs, W. S. C.; Meskers, S. C. J.; Wienk, M. M.; Janssen, R. A. J. Effect of the Fibrillar Microstructure on the Efficiency of High Molecular Weight Diketopyrrolopyrrole-Based Polymer Solar Cells. Adv. Mater. 2014, 26, 1565-1570. (25) Meager, I.; Ashraf, R. S.; Rossbauer, S.; Bronstein, H.; Donaghey, J. E.; Marshall, J.; Schroeder, B. C.; Heeney, M.; Anthopoulos, T. D.; McCulloch, I. Alkyl Chain Extension as a Route to Novel Thieno[3,2-b]thiophene Flanked Diketopyrrolopyrrole Polymers for Use in Organic Solar Cells and Field Effect Transistors. Macromolecules 2013, 46, 5961-5967. (26) Yiu, A. T.; Beaujuge, P. M.; Lee, O. P.; Woo, C. H.; Toney, M. F.; Fréchet, J. M. J. Side-Chain Tunability of Furan-Containing Low-Band-Gap Polymers Provides Control of Structural Order in Efficient Solar Cells. J. Am. Chem. Soc. 2012, 134, 2180-2185. (27) Yun, H.-J.; Cho, J.; Chung, D. S.; Kim, Y.-H.; Kwon, S.-K. Comparative Studies on the Relations between Composition Ratio and Charge Transport of DiketopyrrolopyrroleBased Random Copolymers. Macromolecules 2014, 47, 7030-7035. (28) Yun, H.-J.; Lee, G. B.; Chung, D. S.; Kim, Y.-H.; Kwon, S.-K. Novel Diketopyrroloppyrrole

Random

Copolymers:

High

Charge-Carrier

Mobility

From

Environmentally Benign Processing. Adv. Mater. 2014, 26, 6612-6616. (29) Choi, H. H.; Baek, J. Y.; Song, E.; Kang, B.; Cho, K.; Kwon, S.-K.; Kim, Y.-H. A Pseudo-Regular Alternating Conjugated Copolymer Using an Asymmetric Monomer: A High-Mobility Organic Transistor in Nonchlorinated Solvents. Adv. Mater. 2015, 27, 36263631. (30) Ji, Y.; Xiao, C.; Wang, Q.; Zhang, J.; Li, C.; Wu, Y.; Wei, Z.; Zhan, X.; Hu, W.; Wang, Z.; Janssen, R. A. J.; Li, W. Asymmetric Diketopyrrolopyrrole Conjugated Polymers 23 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 24 of 30

for Field-Effect Transistors and Polymer Solar Cells Processed from a Nonchlorinated Solvent. Adv. Mater. 2016, 28, 943-950. (31) Gobalasingham, N. S.; Noh, S.; Howard, J. B.; Thompson, B. C. Influence of Surface Energy on Organic Alloy Formation in Ternary Blend Solar Cells Based on Two Donor Polymers. ACS Appl. Mater. Interfaces 2016, 8, 27931-27941. (32) Noh, S.; Gobalasingham, N. S.; Thompson, B. C. Facile Enhancement of OpenCircuit Voltage in P3HT Analogues via Incorporation of Hexyl Thiophene-3-carboxylate. Macromolecules 2016, 49, 6835-6845. (33) Zhou, J.; Xie, S.; Amond, E. F.; Becker, M. L. Tuning Energy Levels of Low Bandgap Semi-Random Two Acceptor Copolymers. Macromolecules 2013, 46, 3391-3394. (34) Binder, J. B.; Raines, R. T. Simple Chemical Transformation of Lignocellulosic Biomass into Furans for Fuels and Chemicals. J. Am. Chem. Soc. 2009, 131, 1979-1985. (35) Gandini, A. Polymers from Renewable Resources: A Challenge for the Future of Macromolecular Materials. Macromolecules 2008, 41, 9491-9504. (36) Gidron, O.; Dadvand, A.; Sheynin, Y.; Bendikov, M.; Perepichka, D. F. Towards "Green" Electronic Materials. [small alpha]-Oligofurans as Semiconductors. Chem. Commun. 2011, 47, 1976-1978. (37) Gidron, O.; Diskin-Posner, Y.; Bendikov, M. α-Oligofurans. J. Am. Chem. Soc. 2010, 132, 2148-2150. (38) Miyata, Y.; Nishinaga, T.; Komatsu, K. Synthesis and Structural, Electronic, and Optical Properties of Oligo(thienylfuran)s in Comparison with Oligothiophenes and Oligofurans. J. Org. Chem. 2005, 70, 1147-1153. 24 ACS Paragon Plus Environment

Page 25 of 30

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

(39) Chen, M. S.; Lee, O. P.; Niskala, J. R.; Yiu, A. T.; Tassone, C. J.; Schmidt, K.; Beaujuge, P. M.; Onishi, S. S.; Toney, M. F.; Zettl, A.; Fréchet, J. M. J. Enhanced Solid-State Order and Field-Effect Hole Mobility through Control of Nanoscale Polymer Aggregation. J. Am. Chem. Soc. 2013, 135, 19229-19236. (40) Li, Y.; Sonar, P.; Singh, S. P.; Zeng, W.; Soh, M. S. 3,6-Di(furan-2-yl)pyrrolo[3,4c]pyrrole-1,4(2H,5H)-dione and Bithiophene Copolymer with Rather Disordered Chain Orientation Showing High Mobility in Organic Thin Film Transistors. J. Mater. Chem. 2011, 21, 10829-10835. (41) Sonar, P.; Chang, J.; Shi, Z.; Gann, E.; Li, J.; Wu, J.; McNeill, C. R. Hole Mobility of 3.56 cm2 V-1 s-1 Accomplished using More Extended Dithienothiophene with Furan flanked Diketopyrrolopyrrole Polymer. J. Mater. Chem. C 2015, 3, 9299-9305. (42) Sonar, P.; Foong, T. R. B.; Singh, S. P.; Li, Y.; Dodabalapur, A. A Furan-Containing Conjugated Polymer for High Mobility Ambipolar Organic Thin Film Transistors. Chem. Commun. 2012, 48, 8383-8385. (43) Sonar, P.; Ha, T.-J.; Seong, Y.; Yeh, S.-C.; Chen, C.-T.; Manzhos, S.; Dodabalapur, A. A Study of Diphenylfumaronitrile and Furan-Substituted Diketopyrrolopyrrole Alternating Copolymer and Its Thin-Film Transistors. Macromol. Chem. Phys. 2014, 215, 725-732. (44) Ha, T.-J; Sonar, P.; Dodabalapur, A. Improved Performance in DiketopyrrolopyrroleBased Transistors with Bilayer Gate Dielectrics. ACS Appl. Mater. Interfaces 2014, 6, 31703175. (45) Ha, T.-J; Sonar, P.; Dodabalapur, A. A Fluorenone based Low Band Gap Solution Processable Copolymer for Air Stable and High Mobility Organic Field Effect Transistors. Chem. Commun. 2013, 49, 1588-1590 25 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 26 of 30

(46) Sonar, P.; Chang, J.; Kim, J. H.; Ong, K.-H.; Gann, E.; Manzhos, S.; Wu, J.; McNeill, C. R. High-Mobility Ambipolar Organic Thin-Film Transistor Processed From a Nonchlorinated Solvent. ACS Appl. Mater. Interfaces 2016, 8, 24325-24330. (47) Lee, J.; Han, A. R.; Kim, J.; Kim, Y.; Oh, J. H.; Yang, C. Solution-Processable Ambipolar Diketopyrrolopyrrole–Selenophene Polymer with Unprecedentedly High Hole and Electron Mobilities. J. Am. Chem. Soc. 2012, 134, 20713-20721. (48) Lee, O. P.; Yiu, A. T.; Beaujuge, P. M.; Woo, C. H.; Holcombe, T. W.; Millstone, J. E.; Douglas, J. D.; Chen, M. S.; Fréchet, J. M. J. Efficient Small Molecule Bulk Heterojunction Solar Cells with High Fill Factors via Pyrene-Directed Molecular SelfAssembly. Adv. Mater. 2011, 23, 5359-5363. (49) Gidron, O.; Varsano, N.; Shimon, L. J. W.; Leitus, G.; Bendikov, M. Study of a Bifuran vs. Bithiophene Unit for the Rational Design of [small pi]-Conjugated Systems. What Have We Learned? Chem. Commun. 2013, 49, 6256-6258. (50) Jeffries-El, M.; Kobilka, B. M.; Hale, B. J. Optimizing the Performance of Conjugated

Polymers

in Organic

Photovoltaic

Cells

by

Traversing

Group

16.

Macromolecules 2014, 47, 7253-7271. (51) Zoombelt, A. P.; Mathijssen, S. G. J.; Turbiez, M. G. R.; Wienk, M. M.; Janssen, R. A. J. Small Band Gap Polymers based on Diketopyrrolopyrrole. J. Mater. Chem. 2010, 20, 2240-2246. (52) Dou, L.; Gao, J.; Richard, E.; You, J.; Chen, C.-C.; Cha, K. C.; He, Y.; Li, G.; Yang, Y. Systematic Investigation of Benzodithiophene- and Diketopyrrolopyrrole-Based LowBandgap Polymers Designed for Single Junction and Tandem Polymer Solar Cells. J. Am. Chem. Soc. 2012, 134, 10071-10079. 26 ACS Paragon Plus Environment

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(53) Kim, B. J.; Lee, H.-S.; Lee, J. S.; Cho, S.; Kim, H.; Son, H. J.; Kim, H.; Ko, M. J.; Park, S.; Kang, M. S.; Oh, S. Y.; Kim, B.; Cho, J. H. Correlation between Crystallinity, Charge Transport, and Electrical Stability in an Ambipolar Polymer Field-Effect Transistor Based on Poly(naphthalene-alt-diketopyrrolopyrrole). J. Phys. Chem. C 2013, 117, 1147911486. (54) Lei, T.; Cao, Y.; Zhou, X.; Peng, Y.; Bian, J.; Pei, J. Systematic Investigation of Isoindigo-Based Polymeric Field-Effect Transistors: Design Strategy and Impact of Polymer Symmetry and Backbone Curvature. Chem. Mater. 2012, 24, 1762-1770. (55) Kline, R. J.; DeLongchamp, D. M.; Fischer, D. A.; Lin, E. K.; Richter, L. J.; Chabinyc, M. L.; Toney, M. F.; Heeney, M.; McCulloch, I. Critical Role of Side-Chain Attachment Density on the Order and Device Performance of Polythiophenes. Macromolecules 2007, 40, 7960-7965. (56) Horner, K. E.; Karadakov, P. B. Chemical Bonding and Aromaticity in Furan, Pyrrole, and Thiophene: A Magnetic Shielding Study. J. Org. Chem. 2013, 78, 8037-8043. (57) Lee, K. C.; Park, W.-T.; Noh, Y.-Y.; Yang, C. Benzodipyrrolidone (BDP)-Based Polymer Semiconductors Containing a Series of Chalcogen Atoms: Comprehensive Investigation of the Effect of Heteroaromatic Blocks on Intrinsic Semiconducting Properties. ACS Appl. Mater. Interfaces 2014, 6, 4872-4882. (58) Giri, G.; DeLongchamp, D. M.; Reinspach, J.; Fischer, D. A.; Richter, L. J.; Xu, J.; Benight, S.; Ayzner, A.; He, M.; Fang, L.; Xue, G.; Toney, M. F.; Bao, Z. Effect of Solution Shearing Method on Packing and Disorder of Organic Semiconductor Polymers. Chem. Mater. 2015, 27, 2350-2359.

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(59) Giri, G.; Verploegen, E.; Mannsfeld, S. C. B.; Atahan-Evrenk, S.; Kim, D. H.; Lee, S. Y.; Becerril, H. A.; Aspuru-Guzik, A.; Toney, M. F.; Bao, Z. Tuning Charge Transport in Solution-Sheared Organic Semiconductors using Lattice Strain. Nature 2011, 480, 504-508. (60) Hansen, C. M. Hansen Solubility Parameters: A user's handbook, Second Ed. CRC Press: Boca Raton, FL, USA, 2007. (61) Subramaniyan, S.; Xin, H.; Kim, F. S.; Jenekhe, S. A. New Thiazolothiazole Copolymer Semiconductors for Highly Efficient Solar Cells. Macromolecules 2011, 44, 6245-6248. (62) Walker, B.; Han, D.; Moon, M.; Park, S. Y.; Kim, K.-H.; Kim, J. Y.; Yang, C., Effect of Heterocyclic Anchoring Sequence on the Properties of Dithienogermole-Based Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 7091-7099. (63) Chen, S.; Lee, K. C.; Zhang, Z.-G.; Kim, D. S.; Li, Y.; Yang, C. An Indacenodithiophene–Quinoxaline Polymer Prepared by Direct Arylation Polymerization for Organic Photovoltaics. Macromolecules 2016, 49, 527-536. (64) Kang, S.-H.; Lee, H. R.; Dutta, G. K.; Lee, J.; Oh, J. H.; Yang, C., A Role of SideChain Regiochemistry of Thienylene–Vinylene–Thienylene (TVT) in the Transistor Performance of Isomeric Polymers. Macromolecules 2017, 50, 884-890. (65) Lee, E. K.; Park, C. H.; Lee, J.; Lee, H. R.; Yang, C.; Oh, J. H., Chemically Robust Ambipolar Organic Transistor Array Directly Patterned by Photolithography. Adv. Mater. 2017, 29, 1605282.

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(66) Kim, J.; Han, A. R.; Hong, J.; Kim, G.; Lee, J.; Shin, T. J.; Oh, J. H.; Yang, C., Ambipolar Semiconducting Polymers with π-Spacer Linked Bis-Benzothiadiazole Blocks as Strong Accepting Units. Chem. Mater. 2014, 26, 4933-4942.

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Table of Contents (TOC)

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