Influence of Branched Alkyl Ester-labelled Side-chains on Specific

Subscriber access provided by Kaohsiung Medical University

Organic Electronic Devices

Influence of Branched Alkyl Ester-labelled Side-chains on Specific Chain Arrangement and Charge Transport Properties of Diketopyrrolopyrrole-based Conjugated Polymers Hyung Jong Kim, Mingyuan Pei, Joong Se Ko, Min Hee Ma, Gi Eun Park, Jimin Baek, Hoichang Yang, Min Ju Cho, and Dong Hoon Choi ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b13292 • Publication Date (Web): 01 Nov 2018 Downloaded from http://pubs.acs.org on November 1, 2018

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

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

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

ACS Applied Materials & Interfaces

Influence of Branched Alkyl Ester-labelled Sidechains on Specific Chain Arrangement and Charge Transport Properties of Diketopyrrolopyrrole-based Conjugated Polymers Hyung Jong Kim1,†, Mingyuan Pei2, †, Joong Se Ko2, Min Hee Ma1, Gi Eun Park1, Jimin Baek2, Hoichang Yang2,*, Min Ju Cho1,*, Dong Hoon Choi1,* 1Department

of Chemistry, Research Institute for Natural Sciences, Korea University, Seoul 02841, South Korea, 2Department

of Applied Organic Materials Engineering, Inha University, Incheon 22212, South

Korea.

Abstract

A series of diketopyrrolopyrrole (DPP)-based copolymers, with DPP and bithiophene (BT) as the electron acceptor and donor backbone units, respectively, is synthesized with branched alkyl side-chains that are either directly coupled to the N-positions of DPP or separated by an alkyl ester group. The ester moieties in the side-chains induce specific cohesive molecular interactions between these side-chains, as compared to the alkyl-only side-chains with weak van der Waals interactions. Structure analysis of the DPPBT-based copolymers demonstrated that the introduction of a proper alkyl ester spacer to the branched alkyl chains can shorten the -

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 37

stacking distance between the DPPBT backbones down to 3.61 Å and promote the development of two-dimensionally extended domains. DPPBT-based copolymers, including different branched alkyl ester-labelled side-chains, are spun-cast on polymer-treated SiO2 dielectrics from dilute chloroform solutions for organic thin film transistors. A DPPBT-based copolymer with properly engineered side-chains (i.e., 2-decyltetradecyl ester-labelled side-chains) shows the highest hole mobility of 2.30 cm2 V-1 s-1 and an on/off current ratio of above 106.

Keywords: diketopyrrolopyrrole, side-chain engineering, cohesive side-chain interaction, alkyl ester, conjugated polymer, organic thin film transistor

1. INTRODUCTION Solution-processable semiconducting polymers have been studied extensively for various optoelectronic applications, owing to their great potential to achieve low-cost fabrication, large area deposition, and flexibility of devices.1-13 Among organic semiconductors, π-conjugated polymers have recently demonstrated highly promising electrical properties in organic thin film transistors (OTFTs), specifically, a charge-carrier mobility () that is much greater than the 0.5  1.0 cm2 V-1 s-1 found in amorphous silicon-based TFTs.14-19 It is known that semiconducting polymers composed of repeating units with alternating electron donor and acceptor can facilitate better charge-carrier transport due to intra- and inter- chain interactions.17-20 In this case, diketopyrrolopyrrole (DPP) derivatives have been popular as A units, due to their planar fusedring structures and strong intermolecular interactions.21


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


There are two general design strategies of these D-A polymers, specifically, DPP-based copolymers reported elsewhere. The first strategy is to design and synthesize novel D backbone moieties, including various conjugated groups or linkages, that precisely modulate the optoelectrical properties of the resulting copolymers.22-26 Another strategy is to introduce a precisely engineered linear alkyl side-chain at the N-positions of the DPP units located in the conjugated copolymers. In comparison to linear alkyl side-chains, branched alkyl substituents (e.g., 2-hexyldecyl (HD), 2-octyldodecyl (OD), and 2-decyltetradecyl (DD)) are highly effective in improving the solubility and crystalline chain packing behavior without significantly altering the intra- and inter-molecular ordering of side-chain-engineered conjugated copolymers.27-29 Recently, many studies have focused on improving the carrier mobility in OTFTs by optimizing the size and bifurcation points of bulky branched alkyl chains on the conjugated backbone segments.30-32 For example, Kim et al. controlled the bifurcation points of long alkyl side-chains on DPP moieties in D-A conjugated copolymers. They reported that π-π overlapping and localized ordering of the DPP-based copolymers were significantly improved with increasing distance of the bifurcation points of the alkyl side units from the polymer backbones, yielding  values up to 5.2 cm2 V-1 s-1 in spun-cast polymer film-based OTFTs.33-36 Wang et al. reported DPP-based copolymers with asymmetric alkyl substituents: one branched and another linear chains at each DPP unit.37 The presence of linear alkyl chains in the DPP units could improve the - overlapping between the copolymer chains, yielding  values up to 9.4 cm2 V-1 s-1 in OTFTs. In addition, a few studies have focused on alkyl side-chains with specific functional ends that act as electronegative atoms or groups.38-40 Lee et al. reported that DPP-based copolymers with siloxane-bridged alkyl side-chains could facilitate better π-π overlap, producing high hole and 3 ACS Paragon Plus Environment


Page 4 of 37

electron mobilities in OTFTs.39 Recently, Yao et al. demonstrated that DPP-based copolymers with urea-bridged alkyl side-chains could exhibit good electrical properties.40 Although these kinds of DPP-based copolymers showed high performance in OTFTs, it is difficult to prepare these alkyl groups because of their complicated synthesis routes. Additionally, there are limited studies related to the structures of DPP-based copolymers including alkyl side-chains with polar functional units, which can induce other interactions besides van der Waals interactions. Hydrogen bonds are strong molecular interactions, and are a key feature of various ordered structures, such as proteins.41-42 Hydrogen bonds are formed when a proton can be shared by two electronegative atoms, such as nitrogen or oxygen. In addition, various proteins exhibit close contact between a hydrogen bonded to a -carbon (C-H) and X (where C is a highly polarized methyl and X is an electronegative atom).43 C-H  O type hydrogen bonds are observed mainly in protein structures are well known. Here, we modified alkyl side-chains to include alkyl ester moieties, which can induce C at the nearest methyl group. Novel D-A conjugated copolymers including DPP-bithiophene (DPPBT) derivatives were synthesized with ester-bridged alkyl substituents tethered to the N-positions of the DPP moieties. The electronegative O atom in the ester moiety and the H atom bonded at the C located at the nearest ester moiety can induce intermolecular attraction, resulting in a better conjugated structure in the D-A backbones compared to the hydrocarbon-only side-chain systems, which have weak van der Waal forces.44-46 We synthesized a series of DPPBT-based copolymers bearing alkyl ester-labelled side-chains, which were easily designed via a single-step esterification of two bromoalkanoyl chlorides (i.e., Br-(CH2)3CO-Cl and Br-(CH2)5CO-Cl) and


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


branched alkyl (i.e. OD and DD) alcohols (Scheme 1). Charge-carrier-transport properties of the resulting copolymers, P(ODE3-DPPBT), P(ODE5-DPPBT), P(DDE3-DPPBT), and P(DDE5DPPBT), were characterized and compared to those of P(OD-DPPBT) and P(DD-DPPBT) without ester groups in the branched side-chains. We found that the ester moieties induced relatively strong interactions between these side-chains in comparison to the alkyl-only system with weak van der Waals interactions. The DPPBT-based copolymers were deposited on a polymer-grafted SiO2 dielectric surface from dilute chloroform (CF) solutions. It was shown that the introduction of an additional alkyl ester spacer to branched alkyl chains can shorten the - overlapping distance between the well-ordered DPPBT-based polymer chains down to 3.61 Å and produce ordered side-chains to form two-dimensional (2D) -conjugated domains, originating from the C-H ··· O cohesive interactions. The optimal DPPBT-based copolymer film shows the highest µ value of 2.30 cm2 V-1 s-1 in an OTFT, with a high on/off current ratio (Ion/Ioff > 106).



Page 6 of 37

Scheme 1. Synthetic schemes for four DPPBT-based copolymers.

2. EXPERIMENTAL 2.1 Materials and Synthesis Materials and all other solvents were used without further purification. The DPPBT-based conjugated copolymers were polymerized via multi-step procedures, as reported in the literature (Scheme 1).25 General synthetic procedure for the DPPBT-based copolymers bearing alkyl ester side-chains Tris(dibenzylideneacetone)dipalladium(0) (2.0 μM) and tri(o-tolyl)phosphine (4.0 μM) were added to a toluene solution (12 mL) of compound Cx (C1-C4) (0.1 mM) and 2,56 ACS Paragon Plus Environment

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


bis(trimethylstannyl)thiophene (0.1 mM) under a nitrogen atmosphere. The mixture was stirred at 100 °C for 24 h. After cooling the reaction mixture to room temperature, it was added to vigorously stirred methanol (200 mL). The precipitated solid was filtered and washed with methanol. The crude product was purified using Soxhlet extraction with acetone, hexane, and CF, successively. The CF fraction was concentrated under reduced pressure. The copolymer was then precipitated in methanol and completely dried under vacuum for 24 h to obtain the DPPBT-based copolymers. 2.2 Characterization. 1H nuclear magnetic resonance (NMR) spectra of the intermediate products were obtained with a Bruker 500 MHz spectrometer after dissolving them in deuterated CF (CDCl3, Cambridge Isotope Laboratories, Inc.). Elemental analysis to confirm the C, H, N, and S contents was conducted using an elemental analyzer (Thermo Scientific Flash 2000, Thermo Fisher Scientific). The number average molecular weights (Mn), weight average molecular weights (Mw), and polydispersity indices (PDI, Mw/Mn) of the copolymers synthesized in this study were measured by gel permeation chromatography (Agilent 1200 series GPC) with polystyrene (PS) standards in o-dichlorobenzene at 80 °C. The absorption spectra of DPP-based copolymer solutions and thin films were recorded using an ultraviolet-visible (UV-vis) absorption spectrometer (Agilent 8453, wavelength () = 190 – 1100 nm). The redox potentials of the DPPBT-based copolymer films were monitored by cyclic voltammetry (CV, potentiostat Model EQ161, eDAQ, scan rate = 50 mV s-1).30 In addition, the thermal properties of DPPBT-based copolymers was measured by using differential scanning calorimetry (DSC, Q20, TA Instruments, heating rate = 10 °C min-1).



Page 8 of 37

Atomic force microscopy (AFM, Multimode 8, Bruker) and synchrotron-based grazingincidence X-ray diffraction (GIXD, 6D and 9A beamlines, Pohang Accelerator Laboratory, Korea) were performed on the DPPBT-based copolymer films on polymer-treated SiO2 surfaces.47 We measured the current-voltage (I-V) characteristics of DPPBT-based copolymer OTFTs using an I-V analyzer (Keithley, 4200 SCS). The  and threshold voltage (Vth) parameters were calculated by drain current-gate voltage (ID-VG) transfer curves and the following equation: ID = (W/2L) Ci  (VG - Vth)2; where Ci is the capacitance per unit area (= 10.8 nF cm-2).47 2.3 Sample Preparation. The PS-grafted SiO2 (gPS-SiO2) dielectrics and TFT devices used in this study were fabricated in accordance with the methods described in our previous literature.47 DPPBT-based copolymer films were deposited on the dielectric surfaces from dilute polymer solutions by spin-coating method, where each polymer (3 mg) was dissolved in 1 mL of CF. Some copolymer films were annealed at different temperatures (TAs) of 150 and 250 C each for 30 min. 3. RESULTS AND DISCUSSION 3.1. Synthesis and Characterization of DPPBT-based Copolymers Most studies related to side-chain engineering for semiconducting polymers have been limited to characterizing the material and electrical properties of π-conjugated polymer chains including alkyl side-chains. Proper side-chains substituted to the conjugated backbone moieties can enhance the solubility, flexibility, and specific chain arrangement of the resulting copolymers when solidified from solution.30-36 However, relatively few studies have attempted to functionalize alkyl side-chains.39-40 8 ACS Paragon Plus Environment

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


Here, well-known DPP and BT units were selected as A and D units for organizing the πconjugated polymer backbones, respectively. We investigated the influence of branched alkyl ester-labelled side-chains on the chain arrangement and charge-carrier transport properties of D-A conjugated copolymers. Four different types of branched alkyl ester-labelled side-chains (referred as ODE3, ODE5, DDE3, and DDE5) were introduced to each N-position of the DPP moieties, and the resulting DPPBT-based copolymers were named as follows: P(ODE3-DPPBT), P(DDE3DPPBT), P(ODE5-DPPBT), and P(DDE5-DPPBT), respectively (Figure 1).

OD

DD

OD

DD C10H21 C8H17

C10H21

E3

E3

O

N O

N

O O C8H17

O

O

O

N

S S

C10H21

O

E5

O

O

S

C10H21

C12H25

O

E5

O

C12H25

C8H17

S

S

O

n

P(ODE3-DPPBT)

O C8H17

N

S

S

S

S

O

n

N

O

P(ODE5-DPPBT)

O

C10H21

N

O

O C10H21

O

N

S S

S

S

O

n

P(DDE3-DPPBT)

S

S

S n

P(DDE5-DPPBT)

O O

C12H25

C10H21

C10H21

N

O

C12H25

Figure 1. Chemical structures of the four DPPBT-based copolymers.

To introduce different side-chains at the N-positions on the DPP units, we first synthesized the ester-bifurcated alkyl derivatives (R-Br) by the one-step esterification of bromoalkanoyl chlorides and branched alkyl alcohols according to a reported procedure.48 Intermediates B1 to B4 were synthesized by alkylation of compound A with either E3 or E5. Then, the DPP derivatives C1  C4 were prepared by bromination of B1 to B4 with N-bromosuccinimide (NBS) in high yields of around 80%. These DPP derivatives were confirmed using 1H NMR spectra and elemental 9 ACS Paragon Plus Environment


Page 10 of 37

analysis (Figures S1–S6 in the Supporting Information (SI)). All DPPBT-based copolymers were synthesized via a Pd-catalyzed Stille coupling polymerization of DPP derivatives and 5,5’bis(trimethylstannyl)-2,2’-bithiophene under reaction conditions at 100 °C for 24 h, resulting in high yields (> 80%). In addition, P(OD-DPPBT) and P(DD-DPPBT) were synthesized as reference polymers bearing only the branched alkyl side-chains.28, 49 The four DPPBT-based copolymers, including the alkyl ester-bifurcated side-chains, exhibited better solubility in solvents (e.g., dichloromethane, CF, and chlorobenzene), in comparison to P(OD-DPPBT) and P(DD-DPPBT), which only had branched alkyl side-chains. Mn and PDI values of all the DPPBT-based copolymers determined by the GPC analysis are shown in Table 1. Among the DPPBT-based copolymers, only the P(OD-DPPBT) and P(DD-DPPBT) copolymers showed endotherms that could be attributed to a semi-crystalline melting transition (Figure 2). The peak melting temperature (Tm) of the P(OD-DPPBT) powder was observed at 303.4 C during DSC heating (up to 350 C). P(DD-DPPBT) had a relatively lower Tm of 289.0 C. However, other D-A copolymers with alkyl ester linkers in the side-chain did not show any clear endotherms during heating. The annealing temperature (TA) for the spun-cast DPPBT-based copolymer films was chosen to be below 260 C based on the onset Tm of P(DD-DPPBT) in the DSC heating curve.


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


Figure 2. DSC heating curves of DPPBT-based copolymers (endothermic direction is down).

3.2. Optical and Electrochemical Properties of DPPBT-based Polymers Absorption spectra and CV profiles of the copolymers were measured and displayed in Figures 3 and 4a, respectively. The corresponding parameters are also listed in Table 1. Absorption spectra of the DPPBT-based copolymer solutions and films showed dual characteristic bands in the range of  = 300  1000 nm; low and high intensity bands were evident at  = 400  500 nm and 600  1000 nm, respectively. These bands correspond to π-π* transition and intramolecular charge transfer (ICT) transition, respectively.50-51 Unlike the P(ODDPPBT) and P(DD-DPPBT) solutions, which presented absorption maxima at  (max) = 778 and 780 nm, respectively, the corresponding spun-cast films showed broader and separated absorption 11 ACS Paragon Plus Environment


Page 12 of 37

peaks, originating from the 0-1 and 0-0 transitions (Table 1).34 The max values in the absorption spectra for E3 and E5 spacer-linked side-chain systems for both solutions and films were slightly red-shifted compared to those of P(OD-DPPBT) and P(DD-DPPBT), owing to the minimized geometrical hindrance of the branched alkyl side-chains caused by the insertion of these spacers.31-32, 34-35

Figure 3. Absorption spectra of the DPPBT-based copolymers in (a, c) solutions and (b, d) films. The spun-cast films of P(OD-DPPBT) and P(DD-DPPBT) showed relatively higher onset oxidation potential (Eox) values of +0.86 and +0.84 V, respectively, indicating highest occupied molecular orbital energy level (EHOMO) values of -5.31 and -5.29 eV, respectively (Figure 4). These latter values were calculated from the following equation, EHOMO = -e(Eox + 4.45 V) 12 ACS Paragon Plus Environment

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


(Table 1). In contrast, the EHOMO values of the E3- and E5-spacer polymer systems were shifted to -5.04 and -5.11 eV, respectively. The HOMO levels became higher as the bifurcation points of the OD and DD chains moved away from the DPPBT backbones, suggesting that the alkyl esterlabelled side-chains can induce better conjugated structures for the D-A conjugated backbones.

Figure 4. (a) CV curves and (b) energy level band diagrams for the DPPBT-based copolymers. Table 1. Physical and electrochemical properties of the DPPBT-based copolymers



Polymer P(ODDPPBT) P(DDDPPBT) P(ODE3DPPBT) P(ODE5DPPBT) P(DDE3DPPBT) P(DDE5DPPBT) a

Mn (kDa)

77.4

Absorption (nm) PDI

1.76

solution

2.40

780

196.0

2.69

797

192.8

3.43

719,

778

162.6

782 717, 776 748, 792 739,

789

173.2

2.70

791

177.7

2.36

786

film

798 739, 785 734, 781

λcut-off (nm)

a

Egopt, b

(eV)

Page 14 of 37

Eoxonset,c

Energy level (eV)

(V)

HOMO c

LUMO d

958

1.29

0.86

-5.31

-4.02

906

1.37

0.84

-5.29

-3.92

907

1.37

0.64

-5.09

-3.72

953

1.30

0.60

-5.05

-3.75

905

1.37

0.66

-5.11

-3.74

918

1.35

0.59

-5.04

-3.69

film; b 1240/cut-off; c obtained from CV sample film on Pt electrode; d LUMO = HOMO +

Egopt. Eoxonset of ferrocene = 0.35 eV.

3.3 Specific Chain Arrangement of DPPBT-based Copolymers in Spun-cast Films: Effects of Alkyl Ester Spacers Figures 5 and 6 show typical AFM topographies of the DPPBT-based copolymer films spuncast on the polymer-treated SiO2 surfaces before and after annealing at 150 and 250 C for 30 14 ACS Paragon Plus Environment

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


min, respectively. PDPPBT-based copolymer films showed distinct morphologies depending upon which side-chains were on the D-A conjugated backbones. The as-spun P(OD-DPPBT) and P(DD-DPPBT) films contained irregularly percolated nanodomains (10  30 nm in size) (Figure 5a and Figure 6a) because the fast solvent evaporation (< 10 s) might provide insufficient time to develop well-defined copolymer films from solutions. In comparison to the P(OD-DPPBT) and P(DD-DPPBT) films, as-spun films of the copolymers containing the E3 and E5 spacer-linked side-chains showed better assembled domains, which still had irregularly shaped structures (Figures 5d, 5g, 6d, and 6g).

Figure 5. AFM topographies of (ac) P(OD-DPPBT), (df) P(ODE3-DPPBT), and (gi) P(ODE5-DPPBT) cast films before and after annealing at different TA for 30 min: (a, d, g) asspun, (b, e, h) 150 C, and (c, f, i) 250 C.



Page 16 of 37

Figure 6. AFM topographies of (ac) P(DD-DPPBT), (df) P(DDE3-DPPBT), and (gi) P(DDE5-DPPBT) cast films before and after annealing at different TA for 30 min: (a, d, g) asspun, (b, e, h) 150 C, and (c, f, i) 250 C.

The initial domains in these as-spun films grew into better ordered structures via annealing at high TA. P(OD-DPPBT) and P(DD-DPPBT) copolymers showed typical melting and crystallization behaviors of semi-crystalline polymers (Figure 2). The 250 C-annealed films cold-crystallized at 250 C (below Tm), developing regularly shaped and sized domains (Figures 5c and 6c). Ordering and percolation of these grains improved in the 150- and 250 C-annealed films. Specifically, the 250 C-annealed P(ODE3-DPPBT) and P(ODE5-DPPBT) films showed percolated layers bearing nanoflakes with a step height of about 3 nm, as shown in Figure 5f and 5i; these results were attributed to the alkyl ester spacers (E3 and E5), which separated the bulky


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


OD chains from the conjugated D-A backbones, enhancing self-association of the conjugated polymer chains. Similarly, P(DDE3-DPPBT) formed percolated layers of 2D flake-like grains in both the 150 and 250 C-annealed films (Figures 6e and 6f). In contrast, the long DDE5 sidechains in P(DDE5-DPPBT) degraded the intra- and inter-chain conformation of the conjugated polymer backbones. As shown in Figures 6gi, the AFM topographies of both the as-spun and annealed P(DDE5-DPPBT) films reveal irregularly shaped grains with sizes below 100 nm. The AFM results suggest that proper side-chain engineering can enhance the solubility and intra/inter-molecular chain conformation of the DPPBT-based copolymers. In conjugated polymer thin films, the localized chain orientation used to achieve an efficient charge-carrier transport is crucial to extend the -conjugated polymer textures with fewer defect sites. 2D GIXD patterns and 1D X-ray profiles of these -conjugated semiconducting copolymer films showed typical X-ray reflections (Figures 7 and 8; Figures S7 and S8 in the SI). The structural parameters are summarized in Table 2. 2D GIXD patterns of the DPPBT-based copolymer films supported that the chain conformation and orientation of the D-A copolymers were considerably affected by the different substituents tethered to the N-positions of the DPP derivatives. First, most of polymer chains in the as-spun P(OD-DPPBT) film were oriented with an “edge-on” chain conformation, but some chains formed a “face-on” oriented structure, where the -stacking direction between the conjugated backbones was normal to the dielectric surface (marked as (010)face-on in Figure 7a and Figure S7a in the SI). In addition, 2D GIXD patterns of the annealed P(OD-DPPBT) films displayed strong reflection intensities due to increased crystallinity; the “edge-on” chain 17 ACS Paragon Plus Environment


Page 18 of 37

conformation was more dominant than the “face-on” one, although the as-spun film contained a small amount of the latter oriented chains. In all the P(OD-DPPBT) films, the layer spacing values of (100) crystal plane (d(100) = 2/Q(h00)) were found to be 20.2  20.6 Å. The d(010) value (referred to as the - overlapping distance, d(010)) varied from 3.80 to 3.86 Å depending on the TA (see Table 2). The larger - overlapping distance of P(OD-DPPBT) was mainly related to the bulkiness of the alkyl sidechains closely linked to the D-A backbone, making it difficult to form coplanar and extended chain structures. In contrast, introduction of the alkyl ester spacers between the OD and DPP backbone moieties significantly improved the “edge-on” chain conformation of the D-A conjugated chains in both as-spun and annealed films on polymer-treated SiO2 surfaces. This was comparable to the engineered side-chain D-A copolymer systems with similar alkyl spacer lengths reported elsewhere.34 In addition, OD segments located farther from the -conjugated DA backbones produced better coplanar chain conformations, which resulted in closer d(010) values of 3.61  3.64 Å.34 After annealing the P(ODE3-DPPBT) and P(ODE5-DPPBT) films, the d(100) values of the crystal planes of the backbone chains that were vertically separated by side-chains increased to 27.5  28.6 and 29.5  30.3 Å, respectively. These values were greater than those of P(OD-DPPBT). Interestingly, these values were even higher than those (approximately 26.4 Å) of common D-A copolymers including branched alkyl side-chains with linear alkyl spacers, which have a number of similar carbons corresponding to the E3 and E5 segments.34 The results were attributed to the more cohesive interactions between the C-H and ester segments in comparison to the van der Waals force experienced by methylene groups.42 The strong interactions between the C-H and O=C- segments can lead to extended, aligned conformations 18 ACS Paragon Plus Environment

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


of the ester-linked side-chains, resulting in closer π-π overlap and an extended structure of D-A πconjugated backbones.

Figure 7. 2D GIXD patterns of (ac) P(OD-DPPBT), (df) P(ODE3-DPPBT), and (gi) P(ODE5-DPPBT) cast films before and after annealing at different TA for 30 min: (a, d, g) asspun, (b, e, h) 150 C, and (c, f, i) 250 C.

Unlike the P(OD-DPPBT) series, the P(DD-DPPBT) films displayed less intense, oriented Xray reflections of the (h00) and (010) crystal planes in the 2D GIXD patterns. Specifically, the 19 ACS Paragon Plus Environment


Page 20 of 37

“face-on” oriented chains were increased in the as-spun film and one annealed at 150 C (Figure 8 and Figure S8 in the SI). For the P(DD-DPPBT) films, the d(100) and d(010) values were approximately 23.5  23.8 and 3.84  3.85 Å, respectively. Similar to the P(OD-DPPBT) film, the introduction of the E3 spacers between DD and DPP moieties was found to improve the “edge-on” chain conformation and provide a closer - overlap distance of the D-A conjugated polymer backbones in both the as-spun and annealed films; the d(010) values were determined to be 3.62  3.63 Å. Also, the values of d(100) were 29.4  30.5 and 31.4  32.3 Å for the P(DDE3DPPBT) and P(DDE5-DPPBT) annealed films, respectively. These values were greater than the ~23.8 Å obtained for P(DD-DPPBT). Similarly, the values were even higher than those of the branched alkyl side-chain systems separated by the linear alkyl spacers with a number of similar carbons, corresponding to the E3 and E5 segments. The high charge transport capability of semiconducting polymer films has been mainly associated with the efficiency of the charge-carrier transport along conjugated (1) chain backbones, (2) domains, and (3) grains.47 Sirringhaus et al. also reported that an indacenodithiophene-based D-A copolymer formed an amorphous-like texture film but its highlyplanar chain conformation could yield unexpectedly high  values in OTFTs.19


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


Figure 8. 2D GIXD patterns of (ac) P(DD-DPPBT), (df) P(DDE3-DPPBT), and (gi) P(DDE5-DPPBT) cast films before and after annealing at different TA for 30 min: (a, d, g) asspun, (b, e, h) 150 C, and (c f, i) 250 C.



Page 22 of 37

Table 2. Structural information for the DPPBT-based copolymer films

P(ODDPPBT)

P(ODE3DPPBT)

P(ODE5DPPBT)

TA (C)

d(100) (Å)

d(010) (Å)

TA (C)

d(100) (Å)

d(010) (Å)



20.2

3.81



23.5

3.84

150

20.5

3.80

150

23.8

3.84

250

20.6

3.86

250

23.5

3.85



28.3

3.63



29.4

3.63

150

28.6

3.64

150

30.5

3.62

250

27.5

3.63

250

30.1

3.62



29.5

3.62



32.3

3.62

150

30.3

3.61

150

31.9

3.62

250

30.3

3.62

250

31.4

3.62

P(DDDPPBT)

P(DDE3DPPBT)

P(DDE5DPPBT)

3.4 Charge-carrier Transport Properties of DPPBT-Based Copolymers In our study, solution-cast DPPBT-based copolymer films could be controlled to develop various ordered structures depending on the side-chains. P(OD-DPPBT) and P(DD-DPPBT) without alkyl ester spacers formed conjugated domains with a larger - overlap distance of 3.80 to 3.86 Å, while the corresponding alkyl ester-linked systems formed self-assembled structures with much smaller d(010) values of 3.61 to 3.64 Å. I-V characteristics of top-contact S/D electrode OTFTs containing DPPBT-based films (channel length, L = 100 m and channel width, W = 22 ACS Paragon Plus Environment

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


1500 m) were measured. Figure 9 shows typical IDVG transfer curves for these OTFTs; some devices had a VG-sweep hysteresis. The  values for DPPBT-based OTFTs are summarized in Figure 10, and other device parameters are shown in Table 3. The P(OD-DPPBT) film-based OTFTs yielded  values ranging from 0.28 to 0.62 cm2 V-1 s-1. The P(ODE3-DPPBT) based OTFTs showed higher  values of 0.35  0.84 cm2 V-1 s-1, which is due to an enhancement in conjugated ordering, specifically, “edge-on” chain conformation of the copolymer along the two electrodes. In addition, the P(ODE5-DPPBT) with the longest alkyl ester (E5) spacer showed significantly enhanced  values in OTFTs, specifically, the 250 C-annealed film exhibited the highest  value of 1.56 cm2 V-1 s-1 (Table 3). As shown in the AFM and 2D GIXD results, the P(ODE5-DPPBT) films that included the long-range ordered “edge-on” chain conformation showed considerable enhancement in charge-carrier transport. However, the P(DD-DPPBT) system had  values of around 0.80 cm2 V-1 s-1 (for as-spun film) in the OTFT, which was much higher than that (0.28 cm2 V-1 s-1) of the as-spun P(OD-DPPBT)based devices, and the 250 C-annealed film-based OTFTs could yield  values up to 1.52 cm2 V1

s-1. The optimal P(DDE3-DPPBT) film annealed at 150 °C showed excellent device

performance, presenting a  value of approximately 2.30 cm2 V-1 s-1, a Vth of -1.8 V, and an Ion/Ioff of about 105. In contrast, the P(DDE5-DPPBT) films showed relatively degraded electrical performance in comparison to the P(DDE3-DPPBT) system. Optimized P(DDE5-DPPBT) OTFTs showed  values up to 2.0  0.30 cm2 V-1 s-1, specifically, for the 250 °C-annealed film. For OTFTs, efficient charge-carrier transport is expected along the - overlapped textures of organic semiconductors between the two electrodes. In this case, the charge-carrier mobility is 23 ACS Paragon Plus Environment


Page 24 of 37

significantly enhanced by the small - overlapping distance and planar chain conformation. conjugated domains with significantly smaller - stacking distances for the E3- and E5-spacer linked side-chain systems created an efficient conducting path for carrier hopping along semiconducting polymer chains due to the ester group-induced attraction between the sidechains. The branched alkyl DD chains that were tethered by the optimal alkyl spacer to the D-A backbones yielded better intra- and inter-molecular - overlap, producing high performance OTFTs.

Figure 9. ID-VG transfer curves for (a) P(OD-DPPBT), (b) P(ODE3-DPPBT), (c) P(ODE5DPPBT), (d) P(DD-DPPBT), (e) P(DDE3-DPPBT), and (f) P(DDE5-DPPBT)-based OTFTs (at drain voltage = -40 V). 24 ACS Paragon Plus Environment

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


Figure 10. Variations in  of OTFTs made from the DPPBT-based copolymer films before and after annealing.



Page 26 of 37

Table 3. Electrical performance of DPPBT-based OTFTs Polymer

P(OD-DPPBT)

P(ODE3-DPPBT)

P(ODE5-DPPBT)

P(DD-DPPBT)

P(DDE3-DPPBT)

P(ODE5-DPPBT)

TA (C)

 (cm2V-1s-1)

Vth (V)

Ion/Ioff

-

0.28  0.03

-1.50

> 106

150

0.57  0.04

-6.20

~2  105

250

0.62  0.05

2.20

~2  105

-

0.35  0.05

5.10

> 105

150

0.60  0.05

8.70

~2  105

250

0.84  0.06

7.90

~4  105

-

0.50  0.05

0.50

~2  106

150

0.55  0.03

0.10

> 107

250

1.56  0.12

0.10

> 107

-

0.80  0.05

-0.40

~2  104

150

1.42  0.10

-3.0

~104

250

1.52  0.13

-4.4

~104

-

1.10  0.05

1.80

~105

150

2.30  0.21

-0.80

~105

250

1.55  0.23

1.80

~105

-

1.15  0.15

2.60

~104

150

1.36  0.17

-4.20

> 105

250

2.00  0.30

1.70

~2  105

4. CONCLUSIONS


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


Six different diketopyrrolopyrrole (DPP)-based copolymers, including DPP and bithiophene (BT) as electron-acceptor and donor backbone units, respectively, was synthesized to contain branched alkyl side-chains, which were either directly coupled to the N-positions of DPP or separated by an alkyl ester group. It was found that the ester moieties form pseudo-hydrogen bonds with the nearest side-chains in comparison to the alkyl-only system with weak van der Waals forces. DPPBT-based copolymers were spun-cast on polymer-treated dielectrics from dilute chloroform solutions for use as channel materials for OTFTs. The optimized P(DDE3DPPBT) film showed the highest hole mobility of 2.30 cm2 V-1 s-1 with an on/off current ratio greater than 106.

Supporting Information. Synthetic procedure, elemental analysis, 1H NMR spectra, 1D out-ofplane and in-plane X-ray profiles of DPPBT-based D-A copolymer films. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *H. Y. [email protected]; [email protected]; [email protected] Author Contributions ‡

H. J. Kim and M. Pei contributed equally.



Page 28 of 37

ACKNOWLEDGMENT This research was supported by National Research Foundation of Korea (NRF2017R1A2B4009313 and NRF2012R1A2A1A01008797) and Key Research Institute Program (NRF20100020209) ABBREVIATIONS DPP, diketopyrrolopyrrole; BT, bithiophene; D-A, donor-acceptor; OTFT, organic thin film transistor; , charge-carrier mobility; HD, 2-hexyldecyl; OD, 2-octyldodecyl; DD, 2decyltetradecyl; C, -carbon; CF, chloroform; CV, cyclovoltammetry; DSC, differential scanning calorimetry; AFM, atomic force microscopy; GIXD, grazing-incidence X-ray diffraction; VD, drain voltage; Vth, threshold voltage; Mn, number-average molecular weight; Mw, weight-average molecular weight; Tm, melting temperature.

5. REFERENCES 1. McCulloch, I.; Heeney, M.; Bailey, C.; Genevicius, K.; MacDonald, I.; Shkunov, M.; Sparrowe, D.; Tierney, S.; Wagner, R.; Zhang, W. M.; Chabinyc, M. L.; Kline, R. J.; Mcgehee, M. D.; Toney, M. F. Liquid-Crystalline Semiconducting Polymers with High Charge-Carrier Mobility. Nat. Mater. 2006, 5, 328-333. 2. Liang, Y.; Wu, Y.; Feng, D.; Tsai, S.-T.; Son, H.-J.; Li, G.; Yu, L. Development of New Semiconducting Polymers for High Performance Solar Cells. J. Am. Chem. Soc. 2009, 131, 5657.


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


3. Hou, J.; Chen, H.-Y.; Zhang, S.; Chen, R. I.; Yang, Y.; Wu, Y.; Li, G. Synthesis of a Low Band Gap Polymer and Its Application in Highly Efficient Polymer Solar Cells. J. Am. Chem. Soc. 2009, 131, 15586-15587. 4. Liang, Y.; Xu, Z.; Xia, J.; Tsai, S.-T.; Wu, Y.; Li, G.; Ray, C.; Yu, L. For the Bright FutureBulk Heterojunction Polymer Solar Cells with Power Conversion Efficiency of 7.4%. Adv. Mater. 2010, 22, E135-E138. 5. Arias, A. C.; MacKenzie, J. D.; McCulloch, I.; Rivnay, J.; Salleo, A. Materials and Applications for Large Area Electronics: Solution-Based Approaches. Chem. Rev. 2010, 110, 324. 6. Li, L.; Gao, P.; Schuermann, K. C.; Ostendorp, S.; Wang, W.; Du, C.; Lei, Y.; Fuchs, H.; De Cola, L.; Mullen, K.; Chi, L. Controllable Growth and Field-Effect Property of Monolayer to Multilayer Microstripes of an Organic Semiconductor. J. Am. Chem. Soc. 2010, 132, 8807-8809. 7. Li, J.; Zhao, Y.; Tan, H. S.; Guo, Y. L.; Di, C.-A.; Yu, G.; Liu, Y. Q.; Lin, M.; Lim, S. H.; Zhou, Y.; Su, H.; Ong, B. S. A Stable Solution-Processed Polymer Semiconductor with Record High-Mobility for Printed Transistors. Sci. Rep. 2012, 2, 00754. 8. Chung, S.; Jang, M.; Ji, S.-B.; Im, H.; Seong, N.; Ha, J.; Kwon, S.-K.; Kim, Y.-H.; Yang, H.; Hong, Y. Flexible High-Performance All-Inkjet-Printed Inverters: Organo-Compatible and Stable Interface Engineering. Adv. Mater. 2013, 25, 4773-4777.



Page 30 of 37

9. Guo, X.; Zhou, N.; Lou, S. J.; Smith, J.; Tice, D. B.; Hennek, J. W.; Ortiz, R. P.; Navarrete, J. T. L.; Li, S.; Strzalka, J.; Chen, L. X.; Chang, R. P. H.; Facchetti, A.; Marks, T. J. Polymer Solar Cells with Enhanced Fill Factors. Nat. Photonics 2013, 7, 825-833. 10. Yuan, Y. B.; Giri, G.; Ayzner, A. L.; Zoombelt, A. P.; Mannsfeld, S. C. B.; 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. Nat. Commun. 2014, 5, 3005. 11. Cho, Y. J.; Yook, K. S.; Lee, J. Y. High Efficiency in a Solution-Processed Thermally Activated Delayed-Fluorescence Device Using a Delayed-Fluorescence Emitting Material with Improved Solubility. Adv. Mater. 2014, 26, 6642-6646. 12. Xie, G.; Li, X.; Chen, D.; Wang, Z.; Cai, X.; Chen, D.; Li, Y.; Liu, K.; Cao, Y.; Su, S.-J. Evaporation- and Solution-Process-Feasible Highly Efficient Thianthrene-9,9',10,10'-TetraoxideBased Thermally Activated Delayed Fluorescence Emitters with Reduced Efficiency Roll-Off. Adv. Mater. 2016, 28, 181-187. 13. Ban, X.; Zhu, A.; Zhang, T.; Tong, Z.; Jiang, W.; Sun, Y. Highly Efficient All-SolutionProcessed Fluorescent Organic Light-Emitting Diodes Based on a Novel Self-Host Thermally Activated Delayed Fluorescence Emitter. ACS Appl. Mater. Interfaces 2017, 9, 21900-21908. 14. Sirringhaus, H. Device Physics of Solution-Processed Organic Field-Effect Transistors. Adv. Mater. 2005, 17, 2411-2425.


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


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. Park, S.; Lim, B. T.; Kim, B.; Son, H. J.; Chung, D. S. High Mobility Polymer Based on a π-Extended Benzodithiophene and Its Application for Fast Switching Transistor and High Gain Photoconductor. Sci. Rep. 2014, 4, 5482. 17. Sun, B.; Hong, W.; Yan, Z.; Aziz, H.; Li, Y. Record High Electron Mobility of 6.3 cm2V-1s1

Achieved for Polymer Semiconductors Using a New Building Block. Adv. Mater. 2014, 26,

2636-2642 18. Kim, G.; Kang, S.-J.; Dutta, G. K.; Han, Y.-K.; Shin, T. J.; Noh, Y.-Y.; Yang, C. A Thienoisoindigo-Naphthalene Polymer with Ultrahigh Mobility of 14.4 cm2/V·s That Substantially Exceeds Benchmark Values for Amorphous Silicon Semiconductors. J. Am. Chem. Soc. 2014, 136, 9477-9483. 19. Chen, H.; Hurhangee, M.; Nikolka, M.; Zhang, W.; Kirkus, M.; Neophytou, M.; Cryer, S. J.; Harkin, D.; Hayoz, P.; Abdi-Jalebi, M.; McNeill, C. R.; Sirringhaus, H.; McCulloch, I. Dithiopheneindenofluorene (TIF) Semiconducting Polymers with Very High Mobility in FieldEffect Transistors. Adv. Mater. 2017, 29, 1702523. 20. Lei, T.; Dou, J.-H.; Pei, J. Influence of Alkyl Chain Branching Positions on the Hole Mobilities of Polymer Thin-Film Transistors. Adv. Mater. 2012, 24, 6457-6461.



Page 32 of 37

21. Yi, Z.; Wang, S.; Liu, Y. Design of High-Mobility Diketopyrrolopyrrole-Based πConjugated Copolymers for Organic Thin-Film Transistors. Adv. Mater. 2015, 27, 3589-3606. 22. Yun, H.-J.; Choi, H. H.; Kwon, S.-K.; Kim, Y.-H.; Cho, K. Conformation-Insensitive Ambipolar Charge Transport in a Diketopyrrolopyrrole-Based Co-polymer Containing Acetylene Linkages. Chem. Mater. 2014, 26, 3928-3937. 23. Lee, T. W.; Lee, D. H.; Shin, J.; Cho, M. J.; Choi, D. H. π-Conjugated Polymers Derived from

2,5-Bis-(2-Decyltetradecyl)-3,6-di(Selenophen-2-yl)Pyrrolo[3,4-c]Pyrrole-1,4(2H,5H)-

Dione for High-Performance Thin Film Transistors. Polym. Chem. 2015, 6, 1777-1785. 24. Zhang, A.; Xiao, C.; Wu, Y.; Li, C.; Ji, Y.; Li, L.; Hu, W.; Wang, Z.; Ma, W.; Li, W. Effect of Fluorination on Molecular Orientation of Conjugated Polymers in High Performance FieldEffect Transistors. Macromolecules 2016, 49, 6431-6438. 25. Zhang, W.; Mao, Z.; Huang, J.; Gao, D.; Yu, G. High-Performance Field-Effect Transistors Fabricated with Donor-Acceptor Copolymers Containing S···O Conformational Locks Supplied by Diethoxydithiophenethenes. Macromolecules 2016, 49, 6401-6410. 26. Lee, J. H.; Park, G. E.; Choi, S.; Lee, D. H.; Um, H. A.; Shin, J.; Cho, M. J.; Choi, D. H. Effect of the Thiophene and Selenophene Moiety in Regular Terpolymers on the Performance of Thin Film Transistors and Polymer Solar Cells. Polymer 2016, 94, 43-52. 27. 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.


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


28. Ha, J. S.; Kim, K. H.; Choi, D. H. 2,5-Bis(2-Octyldodecyl)Pyrrolo[3,4-c]Pyrrole-1,4(2H,5H)-Dione-Based Donor-Acceptor Alternating Copolymer Bearing 5,5 '-Di(Thiophen-2-yl)2,2 '-Biselenophene Exhibiting 1.5 cm2·V-1·s-1 Hole Mobility in Thin-Film Transistors. J. Am. Chem. Soc. 2011, 133, 10364-10367. 29. Kang, I.; An, T. K.; Hong, J.-A.; 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. Adv. Mater. 2013, 25, 524-528. 30. Shin, J.; Park, G. E.; Lee, D. H.; Um, H. A.; Lee, T. W.; Cho, M. J.; Choi, D. H. Bis(thienothiophenyl) Diketopyrrolopyrrole-Based Conjugated Polymers with Various Branched Alkyl Side Chains and Their Applications in Thin-Film Transistors and Polymer Solar Cells. ACS Appl. Mater. Interfaces 2015, 7, 3280-3288. 31. Meager, I.; Ashraf, R. S.; Mollinger, S.; Schroeder, B. C.; Bronstein, H.; Beatrup, D.; Vezie, M. S.; Kirchartz, T.; Salleo, A.; Nelson, J.; McCulloch, I. Photocurrent Enhancement from Diketopyrrolopyrrole Polymer Solar Cells through Alkyl-Chain Branching Point Manipulation. J. Am. Chem. Soc. 2013, 135, 11537-11540. 32. Chen, S.; Sun, B.; Hong, W.; Aziz, H.; Meng, Y.; Li, Y. Influence of Side Chain Length and Bifurcation Point on the Crystalline Structure and Charge Transport of DiketopyrrolopyrroleQuaterthiophene Copolymers (PDQTs). J. Mater. Chem. C 2014, 2, 2183-2190. 33. 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, 1489614899. 33 ACS Paragon Plus Environment


Page 34 of 37

34. Back, J. Y.; Yu, H.; Song, I.; Kang, I.; Ahn, H.; Shin, T. J.; Kwon, S.-K.; Oh, J. H.; Kim, Y.-H. Investigation of Structure-Property Relationships in Diketopyrrolopyrrole-Based Polymer Semiconductors via Side-Chain Engineering. Chem. Mater. 2015, 27, 1732-1739. 35. 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. J. Mater. Chem. C 2015, 3, 11697-11704. 36. Yu, H.; Kim, H. N.; Song, I.; Ha, Y. H.; Ahn, H.; Oh, J. H.; Kim, Y.-H. Effect of Alkyl Chain Spacer on Charge Transport in N-type Dominant Polymer Semiconductors with a Diketopyrrolopyrrole-Thiophene-Bithiazole Acceptor-Donor-Acceptor Unit. J. Mater. Chem. C 2017, 5, 3616-3622. 37. Wang, Z.; Liu, Z.; Ning, L.; Xiao, M. Yi, Y.; Cai, Z.; Sadhanala, A.; Zhang, G.; Chen, W.; Sirringhaus, H.; Zhang, D. Charge Mobility Enhancement for Conjugated DPP-Selenophene Polymer by Simply Replacing One Bulky Branching Alkyl Chain with Linear One at Each DPP Unit. Chem. Mater. 2018, 30, 3090-3100. 38. Liu, Z.; Zhang, G.; Zhang, D. Modification of Side Chains of Conjugated Molecules and Polymers for Charge Mobility Enhancement and Sensing Functionality. Acc. Chem. Res. 2018, 51, 1422-1432. 39. 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.


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


40. Yao, J.; Yu, C.; Liu, Z.; Luo, H.; Yang, Y.; Zhang, G.; Zhang, D. Significant Improvement of Semiconducting Performance of the Diketopyrrolopyrrole-Quaterthiophene Conjugated Polymer through Side-Chain Engineering via Hydrogen-Bonding. J. Am. Chem. Soc. 2016, 138, 173-185. 41. Yesselman, J. D.; Horowitz, S.; Brooks, C. L.; Trievel, R. C. Frequent Side Chain Methyl Carbon-Oxygen Hydrogen Bonding in Proteins Revealed by Computational and Stereochemical Analysis of Neutron Structures. Proteins 2015, 83, 403-410. 42. Horowitz, S.; Dirk, L. M. A.; Yesselman, J. D.; Nimtz, J. S.; Adhikari, U.; Mehl, R. A.; Scheiner, S.; Houtz, R. L.; Al-Hashimi, H. M.; Trievel, R. C. Conservation and Functional Importance of Carbon-Oxygen Hydrogen Bonding in AdoMet-Dependent Methyltransferases. J. Am. Chem. Soc. 2013, 135, 15536-15548. 43. Derewenda, Z. S.; Lee, L.; Derewenda, U. The Occurrence of C-H ··· O Hydrogen Bonds in Proteins. J. Mol. Biol. 1995, 252, 248-262. 44. Kudret, S.; Van den Brande, N.; Defour, M.; Van Mele, B.; Lutsen, L.; Vanderzande, D.; Maes,

W.

Synthesis

of

Ester

Side

Chain

Functionalized

All-Conjugated

Diblock

Copolythiophenes via the Rieke Method. Polym. Chem. 2014, 5, 1832-1837. 45. Kesters, J.; Verstappen, P.; Raymakers, J.; Vanormelingen, W.; Drijkoningen, J.; D'Haen, J.; Manca, J.; Lutsen, L.; Vanderzande, D.; Maes, W. Enhanced Organic Solar Cell Stability by Polymer (PCPDTBT) Side Chain Functionalization. Chem. Mater. 2015, 27, 1332-1341.



Page 36 of 37

46. Kim, J. Y.; Kim, Y. U.; Kim, H. J.; Um, H. A.; Shin, J.; Cho, M. J.; Choi, D. H. Side-Chain Engineering of Diketopyrrolopyrrole-Based Copolymer Using Alkyl Ester Group for Efficient Polymer Solar Cell. Macromol. Res. 2016, 24, 980-985. 47. Jang, M.; Kim, S. H.; Lee, H.-K.; Kim, Y.-H.; Yang, H., Layer-by-Layer Conjugated Extension of a Semiconducting Polymer for High-Performance Organic Field-Effect Transistor. Adv. Funct. Mater. 2015, 25, 3833-3839. 48. Peng, H.-Q.; Sun, C.-L.; Xu, J.-F.; Niu, L.-Y.; Chen, Y.-Z.; Wu, L.-Z.; Tung, C.-H.; Yang, Q.-Z. Convenient Synthesis of Functionalized Bis-ureidopyrimidinones Based on Thiol-yne Reaction. Chem. Eur. J. 2014, 20, 11699-11702. 49. Li, W.; Hendriks, K. H.; Furlan, A.; Roelofs, W. S. C.; Wienk, M. M.; Janssen, R. A. J. Universal Correlation between Fibril Width and Quantum Efficiency in DiketopyrrolopyrroleBased Polymer Solar Cells. J. Am. Chem. Soc. 2013, 135, 18942-18948. 50. Henson, Z. B.; Welch, G. C.; van der Poll, T.; Bazan, G. C. Pyridalthiadiazole-Based Narrow Band Gap Chromophores. J. Am. Chem. Soc. 2012, 134, 3766-3779. 51. Yin, Q.-R.; Miao, J.-S.; Wu, Z.; Chang, Z.-F.; Wang, J.-L.; Wu, H.-B.; Cao, Y. Rational Design of Diketopyrrolopyrrole-Based Oligomers for High Performance Small Molecular Photovoltaic Materials Via an Extended Framework and Multiple Fluorine Substitution. J. Mater. Chem. A 2015, 3, 11575-11586.


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


SYNOPSIS


Influence of Branched Alkyl Ester-labelled Side-chains on Specific

Recommend Documents