Naphthobisthiadiazole-Based Selenophene-Incorporated

Subscriber access provided by Macquarie University

Organic Electronic Devices

Naphthobisthiadiazole-Based SelenopheneIncorporated Quarterchalcogenophene Copolymers for Field-Effect Transistors and Polymer Solar Cells Fong-Yi Cao, Fang-Yu Lin, Cheng-Chun Tseng, KaiEn Hung, Jhih-Yang Hsu, Yen-Chen Su, and Yen-Ju Cheng ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b00083 • Publication Date (Web): 28 Feb 2019 Downloaded from http://pubs.acs.org on February 28, 2019

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 24 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

Naphthobisthiadiazole-Based

Selenophene-Incorporated

Quarterchalcogenophene

Copolymers for Field-Effect Transistors and Polymer Solar Cells Fong-Yi Cao, Fang-Yu Lin, Cheng-Chun Tseng, Kai-En Hung, Jhih-Yang Hsu, Yen-Chen Su and Yen-Ju Cheng* Department of Applied Chemistry, National Chiao Tung University, 1001 University Road, Hsinchu, 30010 Taiwan E-mail: [email protected] ABSTRACT: In this research, we developed six new selenophene-incorporated naphthobisthiadiazole-based D-A polymers PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT. The structure-property relationships have been systematically established through the comparison of their structural variations: (1) isomeric biselenophene/bithiophene arrangement between PNT2Th2Se and PNT2Se2Th polymers, (2) biselenophene/bithiophene and quarterselenophene donor units between PNT2Th2Se/PNT2Se2Th and PNT4Se polymers, (3) side-chain modification between the OD- and DT-series polymers. The incorporation of selenophene unit in the copolymers induces stronger charge transfer to improve the light-harvesting capability while maintaining the strong intermolecular interactions to preserve the intrinsic crystallinity for high carrier mobility. The OFET device using PNT2Th2Se-OD achieved a high hole-mobility of 0.36 cm2V-1s-1 with an on/off ratio of 1.9×105. The solar cells with PNT2Th2Se-OD:PC71BM exhibited a power conversion efficiency (PCE) of 9.47% with an Voc of 0.68 V, an FF of 67 %, and an impressive Jsc of 20.69 mAcm-2. KEYWORDS: Chalcogenophene, Selenophene, Naphthobisthiadiazole, Polymer solar cells, Organic field-effect transistors.

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

1. INTRODUCTION Alternating donor-acceptor (D-A) copolymers have been widely utilized as solutionprocessable semiconductors for bulk-heterojunction (BHJ) polymer solar cells (PSCs) and organic field-effect transistors (OFETs).1-18 The optical, electrochemical properties and solidstate morphology of D-A copolymers can be tailored through modifying the molecular structures. D-A copolymers containing quarterthiophene (Th4) as the donor (D) and difluorobenzothiadiazole (FBT) as the acceptor (A) have represented one of the most successful polymer architectures for PSCs due to their high crystallinity nature with strong intermolecular interactions.19-33 In 2013, Hsu et al. first reported a Th4FBT-type copolymer (denoted as PTh4FBT) showing a power conversion efficiency (PCE) of 6.82% and high hole OFET mobility of 0.29 cm2V−1s−1.19 Yan et al. further changed the attachment position of the alkyl side chains on the Th4FBT polymer backbone to form PffBT4T-2OD. By changing the solution temperature to control the aggregation of the polymer and form the appropriate morphology, the device using the PffBT4T-2OD:PC71BM blend achieved a superior PCE of 10.8%.20-23 To further optimize the performance of the quaterthiophene-based polymers, utilization of different acceptor units have been attempted. In comparison to FBT, naphtho[1,2-c:5,6-c’]bis[1,2,5]thiadiazole (NT) with two fused benzothiadiazole units has larger planar aromatic structure, higher C2h-symmetry and stronger electron-withdrawing capability which can induce efficient intramolecular charge transfer and promote strong intermolecular packing. In our previous work, we developed a NT-based copolymer PαNDTDTNT exhibiting a high OFET hole mobility of 0.214 cm2V−1s−1and a superior PSC efficiency of 8.01%.24 Takimiya and coworkers reported a Th4NT-based D-A copolymer (denoted as PNTz4T) with more red-shifted absorption compared to the PTh4FBT-based polymer. The PNTz4T-based device also delivered a high PCE over 10% with a high Jsc of 19.4 mAcm-2. 252 ACS Paragon Plus Environment

Page 2 of 24

Page 3 of 24 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

Besides utilizing the quaterthiophene as the electron-rich unit, they also synthesized a

polymer system PTzNTz incorporating NT and thiophene-thiazolothiazole (TzTz) units. The inverted PSCs utilized PTzNTz exhibited high efficiency up to 9%.29 Huang et al. also utilized a thiophene-based building block 2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene (BTTT) to a NT-based copolymer showing high efficiencies.30 Selenophene has similar structural geometry as thiophene. However, seleium has higher polarizability than sulfur and polyselenophene exhibits higher quinoidal population than polythiopehene.34-44 Consequently, in comparison with the corresponding thiophene-based counterparts, the selenophene-based materials generally exhibit narrower optical bandgaps, enhanced light-harvesting ability and stronger intermolecular interactions, resulting in the improved charge carrier mobilities in OFETs and higher photocurrents in OPVs.45-52 It is envisaged that replacing thiophenes with selenophenes can further tailor the electronic

properties

without

affecting

their

high

crystalline

nature

of

the

quaterchalcogenophene-based D-A copolymer. To this end, we designed a new bithiophene/biselenophene/NT-based D-A copolymer PNT2Th2Se-OD which contains two selenophenes and two 2-octyldodecylthiophene (OD) units attached to a NT acceptor (Figure 1) in the repeating unit. Another isomeric polymer PNT2Se2Th-OD, where the NT unit is sandwiched by two 2-octyldodecylselenophene, was also prepared to study the isomeric effect. Moreover, the bithiophene unit in PNT2Se2Th-OD was further replaced by biselenophene unit, leading to the quaterselenophene-based PNT4Se-OD (Figure 1). In order to impart better solubility, the 20-carbon 2-octyldodecyl group in the ODseries polymers was replaced with 24-carbon 2-decyltetradecyl (DT) group to yield the other three corresponding DT-series polymers PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT. Molecular properties of the six polymers have been carefully characterized and analyzed. The OFET device using PNT2Th2Se-OD achieved a high hole-mobility of 0.36 cm2V-1s-1. The inverted solar cell devices with the PNT2Th2Se-OD:PC71BM blend exhibited 3 ACS Paragon Plus Environment


Page 4 of 24

a high power conversion efficiency (PCE) of 9.47% with an open-circuit voltage (Voc) of 0.68 V, a fill factor (FF) of 67 %, and high short-circuit current density (Jsc) of 20.69 mAcm-2.

2. RESULTS AND DISCUSSION C10H21

C8H17

N

S

C10H21

N

Se S

S N

S

C8H17

n

Se

C8H17

N

S

C8H17

n

S

Se

n

C10H21

PNT2Th2Se-DT

S

N

C8H17

C10H21

C12H25

Se

n

S

N S C12H25

S

n

Se

N C8H17

C10H21

PNT4Se-OD

S Se

Se Se

N

N

C10H21 S N N

N

N

Se

PNT2Se2Th-OD

C12H25

N S C12H25

S Se

C10H21

Se S

C10H21

N

N

N

C10H21 S N N

S

S

Se

PNT2Th2Se-OD

C12H25

N

C10H21 S N N

Se Se

Se N

C10H21

PNT2Se2Th-DT

S

N C12H25

n

Se

C10H21

PNT4Se-DT

Figure 1. The chemical structures of PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT. The synthetic route for the monomers and polymers is showed in Scheme 1. The detailed synthetic procedures are depicted in the Supporting information. Stille coupling of 2trimethylstannyl-4-(2-octyldodecyl)selenophene

(1a)

and

2-trimethylstannyl-4-(2-

decyltetradecyl)selenophene (1b) with Br-NT (2) afforded NT2Se-OD and NT2Se-DT, respectively, which were brominated by NBS to form Br-NT2Se-OD and Br-NT2Se-DT. Stille polymerization of Br-NT2Se-OD with 5,5'-bis(trimethylstannyl)-2,2'-bithiophene (2Th) or

5,5'-bis(trimethylstannyl)-2,2'-biselenophene

(2Se)

obtained

PNT2Se2Th-OD

and

PNT4Se-OD, respectively. Similarly, 4,7-bis(5-bromo-4-(2-octyldodecyl)thiophenyl-2-yl)5,6-difluorobenzothiadiazole

(Br-NT2Th-OD)

was

copolymerized

bis(trimethylstannyl)-2,2'-biselenophene (2Se) to form PNT2Th2Se-OD.


with

5,5'-

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


In a similar manner, by using Br-NT2Se-DT and Br-NT2Th-DT as the monomers, the corresponding PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT polymers with 2decyltetradecyl side chains were also prepared for comparison. S

N

R Se

SnMe3

+

N

Pd(PPh3)4 P(t-Bu)3

Br Br

1a (R= OD) 1b (R= DT)

N

S

S

N

CHCl3

N

N

S

S

S

SnMe3

N

S

Se

Se

Br

N

S

Br

Me3Sn

Se

Se

SnMe3

Br-NT2Se-OD (R= OD), 74% Br-NT2Se-DT(R= DT), 76%

N

R

S

N

S Se

N

N

Br

S

Me3Sn S

S

S

Se

Se

N

R

S

S

N

Se Se

N

S

Br-NT2Th-OD (R= OD), 74% Br-NT2Th-DT(R= DT), 76%

*

n

Se R

N

PNT4Se-OD (R= OD), 88% PNT4Se-DT(R= DT), 88%

SnMe3

N

R

S

N

Se

Br R

S

N

S

S N

*

n

R

N

Se

N

R

N

PNT2Se2Th-OD (R= OD), 86% PNT2Se2Th-DT(R= DT), 88%

Pd2(dba)3 P(o-tol)3 chlorobenzene

R

S

Br

Br-NT2Se-OD (R= OD), 74% Br-NT2Se-DT(R= DT), 76%

R

N

Se

N


N

N

R

N

Se R

S

Se

Br

NT2Se-OD (R= OD), 34% NT2Se-DT(R= DT), 38%

Me3Sn

N

R

NBS

Se

Se

toluene

2

OD = 2-octyldodecyl DT= 2-decyltetradecyl

N

R


N

S

N

*

n

Se R

PNT2Th2Se-OD (R= OD), 90% PNT2Th2Se-DT(R= DT), 87%

Scheme 1. Synthetic route of PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2SeDT, PNT2Se2Th-DT and PNT4Se-DT.

Thermogravimetric analysis (TGA) was employed to evaluate the thermal stability of the

polymers.

PNT2Th2Se-OD,

PNT2Se2Th-OD,

PNT4Se-OD,

PNT2Th2Se-DT,

PNT2Se2Th-DT and PNT4Se-DT all have high decomposition temperature (Td) of 404˚C, 378˚C, 401˚C, 403˚C, 371˚C and 396˚C, respectively (Table 1 and Figure S1). From the differential scanning calorimetry (DSC) measurements, all polymers showed neither glass transition temperature (Tg) nor melting point (Tm) (Figure S2) in the scanning range.



Page 6 of 24

PNT2Th2Se-OD exhibited a λmax at 762 nm in solution state, while its isomeric polymer PNT2Se2Th-OD showed a more red-shifted λmax at 810 nm in the UV-Vis absorption spectra. The direct attachment of the two more electron-rich selenophene rings to the NT acceptor in PNT2Se2Th induces stronger intramolecular charge transfer, resulting in the broader and the more red-shifted λmax than PNT2Th2Se-OD. Furthermore, the all-selenophene PNT4Se-OD displayed the most red-shifted λmax at 820 nm. The optical bandgaps of PNT2Th2Se-OD, PNT2Se2Th-OD and PNT4Se-OD are gradually decreased (1.63 eV, 1.46 eV and 1.39 eV, respectively) with the increasing content of selenophene. DT-series polymers exhibited similar absorption behavior with the OD-series polymers. The molecular properties are summarized in Table 1. Table 1. Summary of the intrinsic properties of the six polymers. λmax (nm)

Polymers

Mn (kDa)

PDI

Td (°C)

PNT2Th2Se-OD

51.0

2.2

404

o-DCB 689, 762

Film 660, 720

PNT2Se2Th-OD

39.2

2.9

378

700, 810

PNT4Se-OD

31.0

3.3

401

PNT2Th2Se-DT

64.0

2.6

PNT2Se2Th-DT

96.8

2.6

PNT4Se-DT

55.4

3.7

o-DCB = ortho-dichorobenzene,

λonset (nm)a)

Egopt (eV)b)

EHOMO (eV)

ELUMO (eV)

Egele (eV)

830

1.47

－5.44

－3.81

1.63

680, 755

895

1.41

－5.28

－3.82

1.46

735, 820

723, 777

925

1.36

－5.18

－3.79

1.39

403

691, 757

678, 728

843

1.45

－5.39

－3.83

1.56

371

695, 807

682, 728

895

1.40

－5.33

－3.84

1.49

396

719, 815

706, 775

914

1.36

－5.24

－3.83

1.41

a)calculated

in the solid state,

b)E opt g

= 1240/λonset.

Figure 2. (a) Normalized UV-visible absorption spectra of the six polymers in o-DCB; (b) energy levels of the six polymers and PC71BM estimated by cyclic voltammetry.


Page 7 of 24 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


The UV-visible absorption spectra as a function of temperature were used to investigate the aggregation behavior of the polymers in o-DCB (Figure 3). The λmax of the OD-series polymers (PNT2Th2Se-OD, PNT2Se2Th-OD and PNT4Se-OD) and the DT-series polymers (PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT) were hypsochromically shifted by 96 nm, 122 nm, 54 nm, 99 nm, 151 nm, and 60 nm, respectively, at higher temperature of 150 °C. The vibronic peaks at the longer wavelengths also gradually disappear as the temperature increases. These results indicated that the six polymers has strong aggregation in solution. To quantify the degree of aggregation, we made a plot of IT/I30 as a function of solution temperature. IT is defined as absorbance intensity at the wavelength of 759 nm for PNT2Th2Se-OD and PNT2Th2Se-DT, 810 nm for PNT2Se2Th-OD and PNT2Se2Th-DT, and 820 nm for PNT4Se-OD and PNT4Se-DT at different temperatures of 30, 50, 70, 90, 110, 130 and 150oC The plot of IT/I30 as a function of solution temperature can be used to quantify the degree of aggregation (Figure 4).32,33 The side-chain modification and isomeric arrangement play important roles to dictate the intermolecular interactions. The IT/I30 values of the OD-series polymers are higher than that of the DT-series polymers from 130 to 30oC, suggesting that the OD-series polymers with the shorter side chain have stronger aggregation than the corresponding DT-series polymers.



Figure 3. Normalized UV-visible absorption spectra of (a) PNT2Th2Se-OD, (b) PNT2Se2ThOD, (c) PNT4Se-OD, (d) PNT2Th2Se-OD, (e) PNT2Se2Th-OD and (f) PNT4Se-OD at elevated temperatures from 30°C to 150°C.

Figure 4. Plot of IT/I30 values of the six polymers as function of temperature from 30 to 150oC. Cyclic voltammetry (CV) was used to estimate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels (Table 1 and Figure S3). The HOMO/LUMO of PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT and PNT4Se-DT were estimated to be −5.44/−3.81, −5.28/−3.82, −5.18/−3.79 eV, −5.39/−3.83, −5.33/−3.84 and −5.24/−3.83 eV with the corresponding 8 ACS Paragon Plus Environment

Page 8 of 24

Page 9 of 24 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


electrochemical bandgap of 1.63 eV, 1.46 eV, 1.39 eV, 1.56 eV, 1.49 eV and 1.41 eV, respectively. In the OD-series polymers, PNT2Th2Se-OD has the lowest-lying HOMO level and the largest bandgap, while the quarterselenophene-based PNT4Se-OD showed the highest HOMO energy and the narrowest bandgap. The DT-series polymers exhibited the similar properties as the OD-series polymers. Quantum-chemical calculations were performed with the Gaussian09 suite15 to further understand the molecular orbital properties of the polymers (Figure 5). The dimer molecules denoted as 2(NT2Th2Se), 2(PNT2Se2Th) and 2(NT4Se) (the 2-octyldodecyl and 2decyltetradecyl group are simplified to methyl group) are used for calculation. The electrondensity of HOMO of the three dimers is delocalized on both the NT and the thiophene/selenophene units, while the eletron-density of the LUMO is primarily localized on the electron-deficient NT units. The calculated HOMO/LUMO levels are −5.08 eV/−3.21 eV, −5.04 eV/ −3.25 eV and −5.00 eV/ −3.24 eV for 2(NT2Th2Se), 2(PNT2Se2Th) and 2(NT4Se), respectively, which is qualitatively consistent with the experimental results.

Figure 5. Calculated HOMO/LUMO frontier molecular orbitals of (a) 2(NT2Th2Se), (b) 2(NT2Se2Th) and (c) 2(NT4Se). The OFET devices were fabricated to measure the charge carrier transport properties of the six polymers (Table 2 and Figure 6). The bottom-gate-top-contact devices with the architecture of Si/SiO2/ODTS/Polymer/Au were fabricated and optimized by thermal annealing at 160oC for 10 min. The OFET device using PNT2Th2Se-OD with thermal 9 ACS Paragon Plus Environment


Page 10 of 24

annealing at 160oC showed the highest hole mobility of 0.36 cm2V-1s-1 in the saturation regime with a current on/off ratio of 1.9×105. Furthermore, PNT2Se2Th-OD and PNT4Se-OD OFET devices also showed the decent hole mobilities of 0.10 cm2V-1s-1 and 0.11 cm2V-1s-1, respectively. On the other hand, the OFET device using PNT2Th2Se-DT with the longer side chain displayed the hole mobility of 0.21 cm2V-1s-1, and PNT2Se2Th-DT and PNT4Se-DT showed the similar mobility of 0.03 cm2V-1s-1 and 0.03 cm2V-1s-1, respectively. Table 2. The optimal bottom-gate/top-contact OFET characteristics of the polymer thin films. Polymer

on/off ratio

Vt (V)

Mobilitya (cm2V-1s-1)

PNT2Th2Se-OD

1.9×105

-10.8

0.36 (0.34±0.020)

PNT2Se2Th-OD

2.0×105

-1.2

0.10 (0.09±0.005)

PNT4Se-OD

7.0×105

-9.6

0.11 (0.11±0.01)

PNT2Th2Se-DT

2.3×105

-7.1

0.21 (0.19±0.02)

PNT2Se2Th-DT

9.3×105

-0.9

0.03 (0.07±0.01)

PNT4Se-DT 4.7×104 -9.8 0.03 (0.03±0.004) asaturated mobility. All of the devices treated by thermal annealing at 160°C for 30 min. The average values with standard deviation over 5 cells are shown in parenthesis.

Figure 6. (a) Typical output curves and (b) transfer plots of the bottom-gate/top-contact OFET devices using PNT2Th2Se-OD with thermal annealing at 160oC. To further understand the crystalline nature of polymers, two-dimensional grazingincidence X-ray diffraction (2D-GIWAXS) was employed to analyze the molecular packing of the six polymer thin films. 2D-GIWAXS images of the polymer films were showed in 10 ACS Paragon Plus Environment

Page 11 of 24 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 7. PNT2Th2Se-OD exhibited a (010) diffraction in the in-plane direction at qxy = 1.80 Å-1 corresponding to the periodic π–π stacking with a distance (dπ) of ca. 3.49 Å, indicating that PNT2Th2Se-OD possesses an edge-on crystalline orientation which benefits the charge transport in the direction parallel to the substrate. Similarly, PNT2Se2Th-OD and PNT4SeOD showed high-order lamella peaks in the out-of-plane direction and a π–π signal at qxy = 1.76 Å-1 and qxy = 1.69 Å-1 with the dπ of ca. 3.57 Å and 3.72 Å in the in-plane direction, respectively, indicating that PNT2Se2Th-OD and PNT4Se-OD also adopt edge-on orientations. Due to the smaller size of thiophene, PNT2Th2Se-OD with the alkylthiophene attached to the NT unit may have smaller steric repulsion and higher main-chain coplanarity near the NT region, resulting in shorter π–π stacking distance than PNT2Se2Th-OD with the alkylselenophene attached to the NT unit. The PNT4Se-OD has the largest steric hindrance and thus longest π–π stacking distance. PNT2Th2Se-OD has the strongest π–π signal and the shortest π–π stacking distance (dπ = 3.49 Å) than PNT2Se2Th-OD and PNT4Se-OD, which is responsible for the highest OFET hole-mobility of 0.36 cm2V-1s-1. Among the DT-series, only PNT2Th2Se-DT displayed the π–π signal at qxy = 1.71 Å-1 and a dπ of ca. 3.67 Å in the in-plane direction. It should be noted that PNT2Th2Se-OD shows the shorter π–π distance (dπ = 3.49 Å) as compared to the corresponding PNT2Th2Se-DT counterpart (dπ = 3.67 Å), which is ascribed to the shorter aliphatic DT chain. Therefore, PNT2Th2Se-OD displays strongest aggregation tendency and highest crystallinity. PNT2Se2Th-DT and PNT4Se-DT did not show obvious π–π signals in the in-plane or out-of-plane directions. Consequently, PNT2Th2Se-DT exhibited the highest OFET mobility of 0.21 cm2V-1s-1 in this series.



Figure 7. Two-dimensional GIWAXS images of the (a) PNT2Th2Se-OD, (b) PNT2Se2ThOD, (c) PNT4Se-OD, (d) PNT2Th2Se-OD, (e) PNT2Se2Th-OD and (f) PNT4Se-OD thin films. The solar cell devices using the ITO/ZnO/polymer:PC71BM/MoO3/Ag configuration were fabricated and the characteristics of devices were summarized in Table 3 and Table S1. The external quantum efficiency (EQE) spectra and the J-V curve are shown in Figure 8. The device using the PNT2Th2Se-OD:PC71BM (1:2 in wt%) blend with 5 vol% diphenyl ether (DPE) as the additive showed an impressive power conversion efficiency of 9.47% with a Voc of 0.68 V, an FF of 0.67, and a high Jsc of 20.69 mAcm-2. Notably, the device exhibited high EQE values from 350 to 800 nm with the maximum EQE exceeding 80%. The substantially broadened EQE responses in the UV-visible region is consistent with the intrinsic absorption region of both PNT2Th2Se-OD and PC71BM. The devices using PNT2Se2Th-OD:PC71BM (1:2 in wt %) and PNT4Se-OD:PC71BM (1:2 in wt %) blend with 5 vol % DPE showed a PCE of 5.28 % and 5.55 %, respectively. The lower efficiencies of PNT2Se2Th-OD- and PNT4Se-OD-based devices are mainly due to the relatively poor solubility of PNT2Se2Th-OD and PNT4Se-OD, leading to the unsuitable 12 ACS Paragon Plus Environment

Page 12 of 24

Page 13 of 24 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


morphology of the active layers. Among the OD-polymers, the device with PNT2Th2Se-OD showed the highest Voc of 0.68 V which is attributed to the deepest HOMO level of PNT2Th2Se-OD. Consistently, the device with PNT4Se-OD displayed the lowest Voc of 0.56 V due to the higher-lying HOMO energy level of PNT4Se-OD. PNT2Th2Se-DT, PNT2Se2Th-DT, and PNT4Se-DT with the longer aliphatic branched chain to improve the solubility were also evaluated. Under the identical conditions, the device using the PNT2Th2Se-DT:PC71BM blend (1:2 in wt%) also showed a high PCE of 8.41% with a Voc of 0.66 V, an FF of 0.65, and a Jsc of 19.70 mAcm-2. The slightly decreased performance compared to the PNT2Th2Se-OD device might result from the slightly reduced crystallinity. Nevertheless, the device using PNT2Se2Th-DT:PC71BM blend (1:2 in wt%) showed an improved efficiency of 8.25% with a Voc of 0.68 V, an FF of 0.71, and a Jsc of 17.21 mAcm-2 compared to the corresponding PNT2Se2Th-OD-based device (5.28%). The improvement might be associated with the better solubility of PNT2Se2Th-DT. However, the PNT4Se-DT still encountered the poor solubility and solution processability. Therefore, the PNT4Se-DT:PC71BM-based device showed a decreased PCE of 5.66%. Compared to the all-thiophene PNTz4T counterpart reported in the literature,

28

the

devices using the selenophene-containing PNT2Th2Se-OD:PC71BM (20.69 mAcm-2) and PNT2Th2Se-DT:PC71BM (19.7 mAcm-2) blends with the enhanced light-harvesting ability showed the higher Jsc values than the device with PNTz4T:PC71BM blend (19.4 mAcm-2). However, other selenophene-containing polymers devices showed the inferior Jsc values, which might be ascribed to their relatively poorer solubility leading to the inappropriate morphology. Table 3. Characteristics of PSC devices with the six polymers as the donor materials. Polymer

Polymer:PC71BMa

Voc (V)

Jsc (mA/cm2)

FF (%)

PCE (%)

PNT2Th2Se-OD

1:2

0.68 (0.67±0.01)

20.69 (20.57±0.55)

67.30 (66.61±1.34)

9.47 (9.24±0.17)



Page 14 of 24

0.66 15.18 52.72 5.28 (0.65±0.01) (15.39±0.49) (52.04±0.97) (5.23±0.04) 0.56 15.96 62.05 5.55 PNT4Se-OD 1:2 (0.56±0.00) (15.84±0.12) (61.36±0.69) (5.44±0.10) 0.66 19.70 64.70 8.41 PNT2Th2Se-DT 1:2 (0.66±0.01) (19.09±0.38) (66.17±1.61) (8.33±0.07) 0.68 17.21 70.50 8.25 PNT2Se2Th-DT 1:2 (0.67±0.01) (17.61±0.3) (69.14±1.02) (8.11±0.10) 0.60 16.57 56.98 5.66 PNT4Se-DT 1:2 (0.61±0.01) (17.92±0.25) (54.81±0.82) (6.02±0.09) awith 5 vol % diphenyl ether as the additive. The average values with standard deviation over 10 cells are shown in parenthesis.Device architecture : ITO/ZnO/polymer:PC71BM:MoO3/Ag. PNT2Se2Th-OD

1:2

Figure 8. (a) J-V curves under AM 1.5G illumination at 100 mW/cm2 and (b) EQE spectra of the devices using PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT, and PNT4Se-DT as the donor materials.

The molecular orientations for the polymer:PC71BM (1:2 in wt%) films prepared identially to the device fabrication were investigated by the 2D-GIWAXS (Figure 9). As shown in Figure 9a, the PNT2Th2Se-OD:PC71BM film exhibited strong diffraction in the outof-plane direction at qz = 1.82 Å-1 corresponding to the periodic π–π stacking of the polymers with the dπ of 3.45 Å. Similarly, the PNT2Th2Se-DT:PC71BM film displayed a π–π signal at qz = 1.80 Å-1 with a longer dπ of 3.49 Å. The results suggest that the PNT2Th2Se-OD and PNT2Th2Se-DT polymers adopt face-on  stacking orientations which are advantageous for vertical charge carrier transport in the active layer. Therefore, PNT2Th2Se-OD:PC71BM and PNT2Th2Se-DT:PC71BM devices showed impressive efficiencies of 9.47% and 8.41%, 14 ACS Paragon Plus Environment

Page 15 of 24 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


respectively. Nevertheless, the GIWAXS image of the PNT2Se2Th-OD:PC71BM and PNT4Se-OD:PC71BM films did not show obvious polymer packing signal. Also, the PNT2Se2Th-DT:PC71BM and PNT4Se-DT:PC71BM films showed the weak molecular packing.

Figure 9. Two-dimensional GIWAXS images of the (a) PNT2Th2Se-OD:PC71BM, (b) PNT2Se2Th-OD:PC71BM, (c) PNT4Se:PC71BM-OD, (d) PNT2Th2Se-DT:PC71BM, (e) PNT2Se2Th-OD:PC71BM, and (f) PNT4Se:PC71BM-OD thin films.

3. CONCLUSIONS In summary, we have designed and synthesized six new selenophene-incorporated naphthabisthiadiazole-based D-A copolymers PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4SeOD, PNT2Th2Se-DT, PNT2Se2Th-DT, and PNT4Se-DT. Main-chain modifications including using two isomeric biselenophene/bithiophene moieties and an all-selenophene (quarterselenophene) donor moiety, as well as side-chain modification (2-octyldodecyl vs 2decyltetradecyl) are employed to systematically tailor the molecular properties. PNT2Se2Th 15 ACS Paragon Plus Environment


with the two selenophene units attached to the NT unit shows the stronger intramolecular charge transfer, more red-shift absorption and smaller band gap compared to the isomeric PNT2Th2Se with the thiophene unit attached to the NT unit. The PNT4Se polymers with the all-selenophene donor show the smallest band gaps. PNT2Th2Se-OD exhibits the stronger intermolecular aggregation and higher crystallinity. As a result, the OFET device using PNT2Th2Se-OD achieved a highest hole mobility of 0.36 cm2 V-1 s-1 with an on/off ratio of 1.9×105. The value is one of the highest mobilities among the NT-based D-A copolymers reported in the literature. The PNT2Th2Se-OD:PC71BM-based OPV device also exhibited a highest efficiency of 9.47% with an Voc of 0.68 V, an FF of 67%, and an impressively high Jsc of 20.69 mAcm-2. The DT-based polymers using the longer aliphatic chains have better solubility and processability. However, the longer aliphatic side chains of the DT-based polymers also sterically decrease the π–π stacking distance in the thin films. Therefore, the OFET mobility of DT-based polymers is slightly decreased than that of the OD series. Similarly, PNT2Th2Se-DT showed the highest OFET of 0.21 cm2 V-1 s-1 and highest OPV efficiency of 8.41% among the DT-series polymers. The PNT2Se2Th-DT:PC71BM device also exhibited a decent efficiency of 8.25%. The new selenophene-incorporated NT-based copolymers with broad absorption, strong π–π interactions and good crystallinity have shown promising OFET p-type mobility close to 1 cm2 V-1 s-1and high OPV efficiency close to 10%.

4. EXPERIMENTAL SECTION Fabrication and Characterization of OFETs. 325 nm thick SiO2 was deposited on the n-doped silicon wafer (Ci=11 nFcm-2). The substrates were rinsed by sulfuric acid and hydrogen peroxide (3:1, in vol%) in water with the solution concentration of 30% at room temperature for 1h, followed by 15 min of sonication in DI water. The substrates were heated on a hotplate at 150°C to remove water, followed by UVozone treatment for 30 min. The SiO2 was immersed in a octadecyltrichlorosilane 16 ACS Paragon Plus Environment

Page 16 of 24

Page 17 of 24 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


(ODTS):toluene solution (1:100, vol%) for 3h. The surface of the ODTS-treated Si/SiO2 substrates were washed by acetone and heated for 1h at 100°C. Thin films (40−60 nm in thickness) of polymers were deposited on ODTS treated Si/SiO2 substrates by spin-coating (1000 rpm) with the hot chlorobenzene solutions (10 mg/mL). Thermal annealing was then conducted at 160°C for 10 min, respectively. Gold source and drain electrodes (40 nm in thickness) were deposited by thermal vacuum evaporation on the top of polymer layer to complete the bottom-gate/top-contact OFET devices. Electrical measurements of all OFET devices were carried out at room temperature in air on 4156C (Agilent Technologies). The field-effect mobilies were calculated in the saturation and linear regime by using the equation Ids=(μWCi/2L)(Vg−Vt)2 and Ids=(𝑊/𝐿)𝜇Ci𝑉ds(𝑉g-𝑉t-1/2𝑉ds), respectively, where Ids is the drainsource current, μ is the field-effect mobility, W is the channel width (1 mm), L is the channel length (100 μm), Ci is the capacitance per unit area of the gate dielectric layer, Vg is the gate voltage, and Vt is threshold voltage. Fabrication and Characterization of PSCs. The ITO-coated glass substrate was ultrasonically cleaned in detergent, DI-water, acetone and isopropyl alcohol for 10 min, respectively, and subsequently treated with UV-ozone for 45 min. The ZnO layer (thickness=ca. 40 nm) was prepared by a sol-gel procedure from ZnO precursor solution spin-coated onto ITO-coated glass and followed by thermal annealing at 170°C in air for 30 min.S1 Furthermore, the blending solutions of polymer:PC71BM (1:2, in wt%) with 5 vol% diphenyl ether (DPE) as an additive were spin-coated on top of ITO/ZnO surface to form the active layers and the thickness is ca. 250 nm. After the thermal annealing at 100°C for 10 min in the glove box (N2), the MoO3 layer (7 nm) and silver anode (150 nm) were deposited by thermal evaporation at a pressure below 10-6 torr in sequence. The devices without encapsulation were characterized in the ambient condition. Current-voltage characteristics were measured using a Keithley 2400 SMU under the irradiation of AM 1.5G San-Yi solar simulator with JIS AAA spectrum. The characteristics of the solar cells were 17 ACS Paragon Plus Environment


optimized by testing approximately 25 cells. IPCE spectra were measured using a lock-in amplifier with a current preamplifier under short-circuit conditions with illumination by monochromatic light from a 250 W quartz-halogen lamp (Osram) passing through a monochromator (Spectral Products CM110).

ASSOCIATED CONTENT Supporting information: The details for general measurement and characterization, fabrication of devices, thermal properties, electrochemical properties, OFET characterization, synthesis and NMR spectra ACKNOWLEDGEMENTS We thank the Ministry of Science and Technology and Center for Interdisciplinary Science (CIS) of the National Chiao Tung University, Taiwan, for financial support. We thank the National Center of High-Performance Computing (NCHC) in Taiwan for computer time and facilities. We also thank the National Synchrotron Radiation Research Center (NSRRC), and Dr. U-Ser Jeng and Dr. Chun-Jen Su in at BL23A1 station for the help with the GIWAXS experiments.

REFERENCES (1) Chen, J.; Cao, Y. Development of Novel Conjugated Donor Polymers for HighEfficiency Bulk-Heterojunction Photovoltaic Devices. Acc. Chem. Res. 2009, 42, 1709−1718. (2) Li, Y. Molecular Design of Photovoltaic Materials for Polymer Solar Cells: Toward Suitable Electronic Energy Levels and Broad Absorption. Acc. Chem. Res. 2012, 45, 723−733. (3) Li, Y.; Zou, Y. Conjugated Polymer Photovoltaic Materials with Broad Absorption Band and High Charge Carrier Mobility. Adv. Mater. 2008, 20, 2952−2958. (4) Thompson, B. C.; Frechet, J. M. Polymer-fullerene Composite Solar Cells. Angew. Chem. Int. Ed. 2008, 47, 58−77. (5) Arias, A. C.; MacKenzie, J. D.; McCulloch, I.; Rivnay, J.; Salleo, A. Materials and 18 ACS Paragon Plus Environment

Page 18 of 24

Page 19 of 24 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


Applications for Large Area Electronics: Solution-Based Approaches. Chem. Rev. 2010, 110, 3−24. (6) Cheng, Y.-J.; Yang, S.-H.; Hsu, C.-S. Synthesis of Conjugated Polymers for Organic Solar Cell Applications. Chem. Rev. 2009, 109, 5868−5923. (7) Günes, S.; Neugebauer, H.; Sariciftci, N. S. Conjugated Polymer-Based Organic Solar Cells. Chem. Rev. 2007, 107, 1324−1338. (8) Duan, C.; Huang, F.; Cao, Y. Recent Development of Push–pull Conjugated Polymers for Bulk-heterojunction Photovoltaics: Rational Design and Fine Tailoring of Molecular Structures. J. Mater. Chem. 2012, 22, 10416-10434. (9) He, F.; Yu, L. How Far Can Polymer Solar Cells Go? In Need of a Synergistic Approach. J. Phys. Chem. Lett. 2011, 2, 3102−3113. (10) Zhou, H.; Yang, L.; You, W. Rational Design of High Performance Conjugated Polymers for Organic Solar Cells. Macromolecules 2012, 45, 607−632. (11) Li, G.; Zhu, R.; Yang, Y. Polymer Solar Cells. Nat. Photonics 2012, 6, 153−161. (12) Huo, L.; Hou, J. Benzo[1,2-b:4,5-b’]dithiophene-based Conjugated Polymers: Band Gap and Energy Level Control and their Application in Polymer Solar Cells. Poly. Chem. 2011, 2, 2453-2461. (13) Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-Acceptor Heterojunctions. Science 1995, 270, 1789−1791. (14) Scharber, M. C.; Mühlbacher, D.; Koppe, M.; Denk, P.; Waldauf, C.; Heeger, A. J.; Brabec, C. J. Design Rules for Donors in Bulk-Heterojunction Solar Cells-Towards 10 % Energy-Conversion Efficiency. Adv. Mater. 2006, 18, 789-794. (15) Wu, J.-S.; Cheng, S.-W.; Cheng, Y.-J.; Hsu, C.-S. Donor–Acceptor Conjugated Polymers Based on Multifused Ladder-Type Arenes for Organic Solar Cells. Chem. Soc. Rev. 2015, 44, 1113-1154. (16) Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-Acceptor Heterojunctions. Science 1995, 270, 1789-1791. (17) Zhao, X.; Zhan, X. Electron Transporting Semiconducting Polymers in Organic Electronics. Chem. Soc. Rev. 2011, 40, 3728-3743. (18) Yang, L.; Gu, W.; Lv, L.; Chen, Y.; Yang, Y.; Ye, P.; Wu, J.; Hong, L.; Peng, A.; Huang, H. Triplet Tellurophene-Based Acceptors for Organic Solar Cells. Angew. Chem. 2018, 130, 1108-1114. 19 ACS Paragon Plus Environment


(19) Jheng, J.-F.; Lai, Y.-Y., Wu, J.-S.; Chao, Y.-H.; Wang, C.-L.; Hsu, C.-S. Influences of the Non-Covalent Interaction Strength on Reaching High Solid-State Order and Device Performance of a Low Bandgap Polymer with Axisymmetrical Structural Units. Adv. Mater. 2013, 25, 2445–2451. (20) Hu, H. W.; Jiang, K.; Yang, G. F.; Liu, J.; Li, Z. K.; Lin, H. R.; Liu, Y. H.; Zhao, J. B.; Zhang, J.; Huang, F.; Qu, Y. Q.; Ma, W.; Yan, H. Terthiophene-Based D–A Polymer with an Asymmetric Arrangement of Alkyl Chains That Enables Efficient Polymer Solar Cells. J. Am. Chem. Soc. 2015, 137, 14149−14157. (21) Liu, Y. H.; Zhao, J. B.; Li, Z. K.; Mu, C.; Ma, W.; Hu, H. W.; Jiang, K.; Lin, H. R.; Ade, H.; Yan, H. Aggregation and Morphology Control Enables Multiple Cases of HighEfficiency Polymer Solar Cells. Nat. Commun. 2014, 5, 5293-5300. (22) Li, Z. K.; Jiang, K.; Yang, G. F.; Lai, J. Y. L.; Ma, T. X.; Zhao, J. B.; Ma, W.; Yan, H. Donor Polymer Design Enables Efficient Non-Fullerene Organic Solar Cells. Nat. Commun. 2016, 7, 13094-13102. (23) Zhao, J. B.; Li, Y. K.; Yang, G. F.; Jiang, K.; Lin, H. R.; Ade, H.; Ma, W.; Yan, H. Efficient Organic Solar Cells Processed from Hydrocarbon Solvents. Nature Energy 2016, 1, 15027-15033. (24) Cheng, S.-W.; Chiou, D.-Y.; Tsai, C.-E.; Liang, W.-W.; Lai, Y.-Y.; Hsu, J.-Y.; Hsu, C.S.; Osaka, I.; Takimiya, K.; Cheng, Y.-J. Angular-Shaped 4,9-Dialkyl α- and βNaphthodithiophene-Based Donor–Acceptor Copolymers: Investigation of Isomeric Structural Effects on Molecular Properties and Performance of Field-Effect Transistors and Photovoltaics. Adv. Funct. Mater. 2015, 25, 6131-6143. (25) Osaka,I.; Shimawaki, M.; Mori, H.; Doi, I.; Miyazaki, E.; Koganezawa, T.; Takimiya, K. Synthesis, Characterization, and Transistor and Solar Cell Applications of a Naphthobisthiadiazole-Based Semiconducting Polymer. J. Am. Chem. Soc. 2012, 134, 3498−3507. (26) Kawashima, K.; Osaka, I.; Takimiya, K. Effect of Chalcogen Atom on the Properties of Naphthobischalcogenadiazole-Based π-Conjugated Polymers. Chem. Mater. 2015, 27, 6558−6570. (27) Kawashima, K.; Tamai, Y.; Ohkita, H.; Osaka, I.; Takimiya, K. High-efficiency Polymer Solar Cells with Small Photon Energy Loss. Nat. Commun. 2015, 6, 10085-10094. (28) Vohra, V.; Kawashima, K.; Kakara, T.; Koganezawa, T.; Osaka, I.; Takimiya, K.; Murata, H. Efficient Inverted Polymer Solar Cells Employing Favourable Molecular Orientation. Nature Photon. 2015, 9, 403-408. 20 ACS Paragon Plus Environment

Page 20 of 24

Page 21 of 24 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


(29) Saito, M.; Osaka, I.; Suzuki, Y.; Takimiya, K.; Okabe, T.; Ikeda, S.; Asano, T. Highly Efficient and Stable Solar Cells Based on Thiazolothiazole and Naphthobisthiadiazole Copolymers. Sci. Rep. 2015, 5, 14202-14210. (30) Chen, Z. H.; Cai, P.; Chen, J. W.; Liu, X. C.; Zhang, L. J.; Lan, L. F.; Peng, J. B.; Ma, Y. G.; Cao, Y. Low Band-Gap Conjugated Polymers with Strong Interchain Aggregation and Very High Hole Mobility Towards Highly Efficient Thick-Film Polymer Solar Cells. Adv. Mater. 2014, 26, 2586–2591. (31) Zhang, Z. Y.; Lin, F.; Chen, H.-C.; Wu, H.-C.; Chung, C.-L.; Lu, C.; Liu, S.-H.; Tung, S.-H.; Chen, W.-C.; Wong, K.-T.; Chou, P.-T. A Silole Copolymer Containing a Laddertype Heptacylic Arene and Naphthobisoxadiazole Ｍ oieties for Ｈ ighly Ｅ fficient Polymer Solar Cells. Energy Environ. Sci. 2015, 8, 552–557. (32) Jin, Y. C.; Z. Chen, M.; Dong, S.; Zheng, N. N.; Ying, L.; Jiang, X.-F.; Liu, F.; Huang, F.; Cao, Y. A Novel Naphtho[1,2-c:5,6-c′]Bis([1,2,5]Thiadiazole)-Based NarrowBandgap π-Conjugated Polymer with Power Conversion Efficiency Over 10%. Adv. Mater. 2016, 28, 9811–9818. (33) Zhao, J. B.; Li, Y. K.; Hunt, A.; Zhang, J. Q.; Yao, H. T.; Li, Z. K.; Zhang, J.; Huang, F.; Ade, H.; Yan, H. A Difluorobenzoxadiazole Building Block for Efficient Polymer Solar Cells. Adv. Mater. 2016, 28, 1868–1873. (34) Cao, F.-Y.; Tseng, C.-C.; Lin, F.-Y.; Chen, Y.; Yan, H.; Cheng, Y.-J. SelenopheneIncorporated Quaterchalcogenophene-Based Donor−Acceptor Copolymers To Achieve Efficient Solar Cells with Jsc Exceeding 20 mA/cm2. Chem. Mater. 2017, 29, 10045– 10052. (35) Usta, H.; Facchetti, A.; Marks, T. n-Channel Semiconductor Materials Design for Organic Complementary Circuits. Acc. Chem. Res. 2011, 44, 501-510. (36) Tang, M.; Bao, Z. Halogenated Materials as Organic Semiconductors. Chem. Mater. 2011, 23, 446-455. (37) Park, J.; Jung, E.; Jung, W.; Jo, W. A Fluorinated Phenylene Unit as a Building Block for High-Performance n-Type Semiconducting Polymer. Adv. Mater. 2013, 25, 25832588. (38) Lei, T.; Xia, X.; Wang, J.; Liu, C.; Pei, J. “ Conformation Locked” Strong ElectronDeficient Poly(p-Phenylene Vinylene) Derivatives for Ambient-Stable n-Type FieldEffect Transistors: Synthesis, Properties, and Effects of Fluorine Substitution Position. J. Am. Chem. Soc. 2014, 136, 2135-2141. (39) Briseno, A.; Miao, Q.; Ling, M.; Reese, C.; Meng, H.; Bao, Z.; Wudl, F. 21 ACS Paragon Plus Environment


Page 22 of 24

Hexathiapentacene: Structure, Molecular Packing, and Thin-Film Transistors. J. Am. Chem. Soc. 2006, 128, 15576-15577. (40) Kawashima, K.; Osaka, I.; Takimiya, K. Effect of Chalcogen Atom on the Properties of Naphthobischalcogenadiazole-Based π-Conjugated Polymers. Chem. Mater. 2015, 27, 6558-6570. (41) Hwang, Y. J.; Ren, G.; Murari, N.; Jenekhe, S. n-Type Naphthalene Diimide– Biselenophene Copolymer for All-Polymer Bulk Heterojunction Solar Cells. Macromolecules 2012, 45, 9056-9062. (42) Kang,I.; Yun, H.; Chung, D.; Kwon, S.; Kim, Y. Record High Hole Mobility in Polymer Semiconductors via Side-Chain Engineering. J. Am. Chem. Soc. 2013, 135, 14896-14899. (43) 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. (44) Patra, A.; Bendikov, M. Polyselenophenes. J. Mater. Chem. 2010, 20, 422–433. (45) Dong, T.; Lv, L.; Feng, L.; Xia, Y.; Deng, W.; Ye, P.; Yang, B.; Ding, S.; Facchetti, A.; Dong, H.; Huang, H. Noncovalent Se···O Conformational Locks for Constructing HighPerforming Optoelectronic Conjugated Polymers. Adv. Mater. 2017, 29, 1606025, (46) Saadeh, H. A.; Lu, L.; He, F.; Bullock, J. E.; Wang, W.; Carsten, B.; Yu, L. Polyselenopheno[3,4-b]selenophene for Highly Efficient Bulk Heterojunction Solar Cells. ACS Macro Lett. 2012, 1, 361-365. (47) Zhao, Z. Y.; Yin, Z. H.; Chen, H. J.; Zheng, L. P.; Zhu, C. G.; Zhang, L.; Tan, S. T.; Wang, H. L.; Guo, Y. L.; Tang, Q. X.; Liu, Y. Q. High-Performance, Air-Stable FieldEffect

Transistors

Based

on

Heteroatom-Substituted

Naphthalenediimide-

Benzothiadiazole Copolymers Exhibiting Ultrahigh Electron Mobility up to 8.5 cm V−1 s−1. Adv. Mater. 2017, 29, 1602410-1602415. (48) Ashraf, R. S.; Meager, I.; Nikolka, M.; Kirkus, M.; Planells, M.; Schroeder, B.; Holliday, S.; Hurhangee, M.; Nielsen, C.; Sirringhaus, H.; McCulloch, I. Chalcogenophene Comonomer Comparison in Small Band Gap Diketopyrrolopyrrole-Based Conjugated Polymers for High-Performing Field-Effect Transistors and Organic Solar Cells. J. Am. Chem. Soc. 2015, 137, 1314-1321. (49) Zeng, Z.; Li, Y.; Deng, J. F.; Huang, Q.; Peng, Q. Synthesis and Photovoltaic Performance of Low Band Gap Copolymers based on Diketopyrrolopyrrole and Tetrathienoacene with Different Conjugated Bridges. J. Mater. Chem. A, 2014, 2, 653662. 22 ACS Paragon Plus Environment

Page 23 of 24 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


(50) Dou, L. T.; Chang, W.-H.; Gao, J.; Chen, C.-C.; You, J. B.; Yang, Y. A SeleniumSubstituted Low-Bandgap Polymer with Versatile Photovoltaic Applications. Adv. Mater. 2013, 25, 825–831. (51) Kim, K.-H.; Park, S.; Yu, H.; Kang, H.; Song, I.; Oh, J. H.; Kim, B. J. Determining Optimal Crystallinity of Diketopyrrolopyrrole-Based Terpolymers for Highly Efficient Polymer Solar Cells and Transistors. Chem. Mater. 2014, 26, 6963-6970. (52) Kim, Y.; Cho, H.-H.; Kim, T.; Liao, K.; Kim, B. J. Terpolymer Approach for Controlling the Crystalline Behavior of Naphthalene Diimide-based Polymer Acceptors and Enhancing the Performance of All-polymer Solar Cells. Polym. J. 2016, 48, 517.



TOC


Page 24 of 24

Naphthobisthiadiazole-Based Selenophene-Incorporated

Recommend Documents