A Haptacyclic Carbazole-Based Ladder-Type Non-Fullerene Acceptor

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A Haptacyclic Carbazole-Based Ladder-Type Non-Fullerene Acceptor with Side-Chain Optimization for Efficient Organic Photovoltaics Yu-Tang Hsiao, Chia-Hua Li, Shao-Ling Chang, Soowon Heo, Keisuke Tajima, Yen-Ju Cheng, and Chain-Shu Hsu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b12612 • Publication Date (Web): 10 Nov 2017 Downloaded from http://pubs.acs.org on November 11, 2017

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ACS Applied Materials & Interfaces

A Haptacyclic Carbazole-Based Ladder-Type Non-Fullerene Acceptor with Side-Chain Optimization for Efficient Organic Photovoltaics Yu-Tang Hsiao,1 Chia-Hua Li,1 Shao-Ling Chang,1 Soowon Heo,2 Keisuke Tajima,2 Yen-Ju Cheng*,1 and Chain-Shu Hsu*1 1

Department of Applied Chemistry, National Chiao Tung University, 1001 University Road, Hsinchu, 30010

Taiwan 2

RIKEN Center for Emergent Matter Science (CEMS) 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

E-mail: [email protected]; [email protected] KEYWORD: carbazole, ladder-type, non-fullerene, bulk heterojunction, organic photovoltaics. Abstract: In this research, a haptacyclic carbazole-based dithienocyclopentacarbazole (DTCC) ladder-type structure was formylated to couple with two 1,1-dicyanomethylene-3-indanone (IC) moieties, forming a new non-fullerene acceptor DTCCIC-C17 using a bulky branched 1-octylnonayl side chain at the nitrogen of the embedded carbazole and four 4-octylphenyl groups at the sp3-carbon bridges. The rigid and coplanar main-chain backbone of DTCC core provides a broad light-absorbing window and a higher-lying LUMO energy level, while the bulky flanked side chains to reduce intermolecular interactions make DTCCIC-C17 amorphous with excellent solution processability. The DTCCIC-C17 as an acceptor is combined with a medium

bandgap

polymer

poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di2-thienyl-5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-’]dithiophene-4,8-dione))])

(PBDB-T)

as

the

donor in the active layer to obtain suitable HOMO/LUMO energy alignments and complimentary absorption. The devices with an inverted configuration (ITO/ZnO/active layer/MoO3/Ag) without using aqueous PEDOT:PSS layer were fabricated for better device stability. When the DIO-treated PBDB-T:DTCCIC-C17 active layer was thermally annealed at 50 oC for 10 min, the device achieved a highest efficiency of 9.48% with a high Voc of 0.98 V, a Jsc of 14.27 mA cm-2, and an FF of 0.68. ACS Paragon Plus Environment


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Introduction Bulk heterojunction organic photovoltaic cells (OPVs) containing a p-type donor and an n-type acceptor photoactive materials are promising for renewable energy.1-3 Compared to the enormous p-type polymers which have been synthesized for achieving high-efficiency OPVs over the past decade4, development of n-type electron acceptors have been lagging behind due to the fact that the traditional fullerene-based derivatives (e.g. [6,6]-phenyl-C61(or C71)-butyric acid methyl ester (PC61BM or PC71BM)) with superior electron affinity and electron mobility have been dominating in the n-type materials.5-9 Nevertheless, the fullerene acceptors also have several intrinsic downsides hindering the continuous advance of OPVs. The insufficient light-absorbing ability of fullerenes adversely limits photocurrents of OPVs. The LUMO energy levels of mono-adduct fullerenes are not easily tunable by structural modification. Furthermore, spherical-shaped fullerenes are prone to undergo thermal-induced aggregation resulting in unstable morphology.10-11 It is therefore of importance and desire to develop new non-fullerene n-type acceptors (NFAs) which have already made significant progress in OPVs in the recent two years.12-13 Through versatile molecular engineering and chemical modifications, the organic-based NFAs can be equipped with broader absorption windows, higher-lying LUMO energy levels and tunable optical bandgaps in an aim to enhance both current density (Jsc) and open-circuit voltage (Voc).14-21 Perylene diimide (PDI)22-24 and naphthalene diimide (NDI)25-27 with twisted 3D structural architectures have been used as NFAs with good OPV performances. Over the past few years, we have strived to developing the multifused ladder-type donor (abbreviated as LD) building blocks for creating various donor-acceptor (D-A) conjugated polymers.28-38 The forced coplanarity of the LDs restricts rotational disorder between interannular single bonds to enhance intrinsic charge carrier mobility.39 These ladder-type multifused molecules have attracted increasing attentions again because a new class of NFAs using an electron-rich LD such as hexacyclic indacenodithiophene (IDT)40-45 and heptacyclic indacenodithieno[3,2-b]thiophene (IDTT)46-51 end-capped with two electron-withdrawing acceptors have successfully achieved remarkable efficiencies. In 2010, we first reported a multifused heptacyclic LD denoted as dithienocyclopentacarbazole (DTCC)52-54 where the two thiophenes are covalently fastened and rigidified with the central carbazole core by a carbon bridge (Scheme 1). As a result of this coplanar and extended conjugated structure, the D-A copolymer incorporating ACS Paragon Plus Environment

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the DTCC unit performed the higher OPV efficiency than its corresponding non-fused analogue.52-54 It is envisaged that the DTCC unit can be utilized as a suitable LD for making new non-fullerene acceptors. In this research, a formylated DTCC was coupled with two 1,1-dicyanomethylene-3-indanone (IC) moieties to form a new A-LD-A-type molecule denoted as DTCCIC-C17 (Figure 1). Such an A-LD-A-type architecture induces efficient intramolecular charge transfer (ICT) to extend absorption spectrum to the longer wavelengths. The four 4-octylphenyl bulky side chains at the two sp3-carbon bridges and a branched 1-octylnonayl group (simplified as C17) at the nitrogen can reduce intermolecular interactions without causing main-chain twisting, making DTCCIC-C17 highly soluble. Coincidently, Sun and Chen et al. reported a similar non-fullerene material DTCCIC, which contains an identical main-chain backbone but with different side chains, i.e. four 4-octyloxyphenyl groups at the sp3-carbons and an octyl group (C8) at the nitrogen.55 Such side-chain modifications on the DTCCIC-C17 core structure in this work might further optimize the molecular properties and thus the device performance, which is worthy of further investigation. A

medium

bandgap

polymer

poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di2-thienyl-5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-c’]dithiophene-4,8-dione))]) (PBDB-T, M n = 30 kDa and PDI = 1.5) is chosen as the donor material to combine with the DTCCIC-C17 acceptor in view of forming the appropriate HOMO/LUMO energy alignments and complementary absorption (Figure 1).56-57 The OPV devices with the inverted configuration using the binary PBDB-T:DTCCIC-C17 blend have achieved a highest efficiency of 9.48% which outperformed the DTCCIC-based devices.55

Figure 1. Chemical structures of DTCCIC-C17 and PBDB-T.

ACS Paragon Plus Environment


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Scheme 1. Synthetic route of compound DTCCIC-C17.

Results and discussion The synthetic routes of DTCCIC-C17 is depicted in Scheme 1. The synthesis of compound 1 has been described by our previous work.52-54 Nucleophilic addition to the ester groups in compound 1 by freshly prepared 4-octylphenyl magnesium bromide formed the benzylic alcohols in compound 2 in 77% yield which further carried out intramolecular Friedel-Crafts cyclization in the presence of acetic acid to successfully afford the DTCC (3) in 68% yield. Treatment of 3 with POCl3/DMF gave formylated compound DTCC (4) in 66% yield. The Knoevenagel condensation of compound 4 with 1,1-dicyanomethylene-3-indanone (IC) yielded the final product DTCCIC-C17 in 89% yield. These new compounds were fully characterized by 1H-NMR, 13C-NMR, and HR-MS. DTCCIC-C17 has good solubility in chloroform and o-dichlorobenzene at room temperature. DTCCIC-C17 exhibited a high decomposition temperature (Td) of 346 oC from the thermogravimetric analysis (TGA) (Figure S1). In the differential scanning calorimetry (DSC) measurement, DTCCIC-C17 does not show any melting point or crystallization transition (Figure S2). Interestingly, the DTCCIC with the different side chains, i.e. four 4-octyloxyphenyl groups at the sp3 carbons and an octyl group at the nitrogen exhibits a clear melting point and crystallization point during the heating and cooling measurement of DSC.55 These results suggest that using a bulkier branched 1-octylnonayl group at the nitrogen to attenuate the intermolecular interactions and reduce the tendency of crystallization makes DTCCIC-C17 more amorphous, which is a crucial characteristics for a ACS Paragon Plus Environment

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NFA material in OPVs. This also manifests that the side-chain engineering of a ladder-type NFA is indeed imperative for structural optimization.

Figure 2. (a) UV-vis absorption spectra of DTCCIC-C17 in chlorobenzene solution and in thin film; (b) cyclic voltammogram of DTCCIC-C17 in CH2Cl2 with a ramping rate of 100 mV/s; (c) energy diagram of DTCCIC-C17 and PBDB-T. Table 1. Optical and electrochemical properties of DTCCIC-C17.

a

λmaxsol

λmaxfilm

εmaxa

αa

Egopt

[nm]

[nm]

[M-1cm-1]

[cm-1]

[eV]

[eV]

[eV]

[eV]

655

704

1.9 *105

1.4 *105

1.60

–5.46

–3.65

1.81

HOMO LUMO

EgCV

absorption coefficient The absorption spectra of DTCCIC-C17 measured in chlorobenzene solution and thin film are shown in

Figure 2a and the data are summarized in Table 1. DTCCIC-C17 exhibited broad and strong absorption in the 400-800 nm region with a maximum absorption peak at 655 nm in chlorobenzene solution and 704 nm in the thin film state which are obviously more blue-shifted than those of DICCIC with λmax at 669 and 732 nm.55 This result is consistent with the fact that DTCCIC-C17 with the bulkier 1-octylnonayl group could effectively reduce intermolecular interactions. The electrochemical properties of DTCCIC-C17 in ACS Paragon Plus Environment


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dichloromethane were evaluated using cyclic voltammetry (CV) (Figure 2b). On the basis of the onsets of the oxidation and reduction curves, the HOMO and LUMO energy levels of DTCCIC-C17 were estimated to be –5.46/–3.65 eV which are lower-lying than those of the donor PBDB-T polymer (–5.33 eV and –2.92 eV) to guarantee efficient exciton dissociation. It is also noteworthy that the estimated LUMO energy level of DTCCIC-C17 (–3.65 eV) is higher-lying than its DTCCIC analogue (–3.87 eV), which is advantageous to improving Voc value.55 The large energy offset of 1.73 eV between the LUMO of DTCCIC-C17 and the HOMO of PBDB-T could potentially might result in a high open circuit voltage (Voc) (Figure 2c). The relatively higher-lying LUMO energy level of DTCCIC-C17 is associated with the existence of an embedded aromatic carbazole unit.

Figure 3. (a) Frontier molecular orbitals (HOMO/LUMO) of DTCCIC-C17; (b) top view and side view of the optimized geometry of DTCCIC-C17 calculated by DFT/B3LYP/6-31G. The optimal molecular geometry and frontier molecular orbitals of the DTCCIC-C17 were calculated with the Gaussian09 suite15 employing the B3LYP density functional in combination with the 6-31G(d) basis set. The octyl groups are replaced by methyl groups for simplicity. The electron density of HOMO/LUMO is distributed over the entire π-system (Figure 3a). As can be seen from the side view of the optimal geometry (Figure 3b), DTCCIC-C17 adopts a highly coplanar main-chain conjugated structure which is beneficial for π-electron delocalization to enhance charge mobility. Furthermore, the 4-methylphenyl side chains at the sp3-tetrahedron carbons are aligned out of the conjugated backbones to prevent self-aggregation and ensure sufficient solubility for solution processability. ACS Paragon Plus Environment

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Figure 4 (a) J–V curves and (b) IPCE spectra of devices with the ITO/ZnO/PBDB-T:DTCCIC-C17 (1:1.5 wt%)/MoO3/Ag.

inverted structure

Bulk heterojunction devices with an inverted architecture ITO/ZnO/active layer/MoO3/Ag were fabricated using the PBDB-T:DTCCIC-C17 blend as the active layer. The J-V characteristics and the external quantum efficiency (EQE) spectrum of the optimized devices under simulated 100 mW cm− 2 at AM 1.5G illumination are shown in Figure 4 and Table 2. The device using the PBDB-T:DTCCIC-C17 (1:1.5 in wt%) without any external treatment already delivered a high PCE of 8.16% with a Voc of 0.98 V, a high Jsc of 12.70 mA cm− 2, and a fill factor (FF) of 0.65. The high Voc is mainly attributed to the higher-lying LUMO energy level (–3.65 eV) of DTCCIC-C17 acceptor. By introducing 0.5 v% diiodooctane (DIO) as the processing additive, the device exhibited a higher PCE of 9.02% with a Voc of 0.96 V, a Jsc of 14.03 mA cm− 2

, and an FF of 0.67. When the DIO-treated active layer was further thermally annealed at 50 oC for 10 min,

the device with the active layer area of 0.04 cm2 achieved a highest efficiency of 9.48% with a Voc of 0.98 V, a Jsc of 14.27 mA cm− 2, and an FF of 0.68. This value represents the highest efficiency among the DTCCIC-based NFA materials in the literature. We found that thermal annealing at 50 oC gives the best device results. The device performance decreases when the heating temperature increases to 80 and 100 oC. The detailed conditions and device parameters can be found in Table S1 in the supporting information. The LUMO level of DTCCIC-C17 (-3.65 eV) is higher than the corresponding IDT-based IC-C6IDT42 (-3.91 eV) and IDTT-based ITIC47 (-3.83 eV) due the embedded electron-donating carbazole unit. The higher LUMO level could lead to higher Voc value. Indeed, DTCCIC-C17:PBDB-T-based device showed higher Voc (0.98 V) than the device using the PBDB-T:ITIC system (0.902 V).57 We also fabricated the devices with the 3-fold larger active layer area of 0.12 cm2. This device can also achieve a high efficiency 8.28%. It should be noted that the inverted configuration adopted in this research can perform better device stability ACS Paragon Plus Environment


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compared to the conventional devices mostly used for the non-fullerene material-based research.58 To gain more insight on the thin film morphology, the PBDB-T:DTCCIC-C17 blends prepared as identical to the device fabrication were investigated by the grazing-incidence wide-angle X-ray diffraction (Figure 5). The PBDB-T:DTCCIC-C17 blend showed a (010) peak at qz = 16.01 Å -1 corresponding to the periodic π-π stacking of the PBDB-T polymer with a distance (dπ) of ca. 3.92 Å (Figure 5a). The (010) peak in the out-of-plane direction reveals that the p-type PBDB-T adopts a face-on orientation which is a beneficial feature for vertical charge transport. The PBDB-T:DTCCIC-C17 with 0.5 v% DIO exhibited a (010) peak at qz = 16.17 Å -1 with a reduced dπ of ca. 3.88 Å (Figure 5b). When the DIO-treated PBDB-T:DTCCIC-C17 blend was thermally annealed at 50 oC for 10 min, the (010) peak shifted to at 16.29 Å -1 corresponding to a dπ of 3.86 Å (Figure 5c). The shortening π-π stacking distance might account for the improvement of the device characteristics. The corresponding 1-D out-of-plane GIWAXS patterns are also shown in Figure 5d.

Figure 5. 2-Dimensional GIWAXS images of the blend films; (a) pristine PBDB-T:DTCCIC-C17 (1:1.5 in wt%) blend; (b) PBDB-T:DTCCIC-C17 (1:1.5 in wt%) blend with 0.5 v% DIO; (c) PBDB-T:DTCCIC-C17 blend (1:1.5 in wt%) with 0.5 v% DIO and thermal annealing at 50 oC for 10 min; (d) the corresponding 1-D out-of-plane GIWAXS.

Table 2. Photovoltaic parameters of the ITO/ZnO/PBDB-T:DTCCIC-C17/MoO3/Ag devices. PBDB-T:DTCCIC-C17

Vocd

Jscd

FFd

PCEd

(1:1.5 in wt%)

(V)

(mA cm−2)

(%)

(%)


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Pristine 0.5 v% DIO 0.5 v% DIOc 0.5 v% DIOc a

0.970 ± 0.001

12.93 ± 0.14

65.15 ± 0.77

8.13 ± 0.03

(0.980)

(12.70)

(65.55)

(8.16)a

0.960 ± 0.001

13.70 ± 0.39

67.88 ± 1.09

8.93 ± 0.11

(0.960)

(14.03)

(66.95)

(9.02)a

0.970 ± 0.001

14.26 ± 0.04

64.08 ± 1.66

9.25 ± 0.29

(0.970)

(14.27)

(67.82)

(9.48)a

0.96

12.64

68.3

8.28b

parameters from the devices with the defined active layer of 0.04 cm2. bparameters from the larger devices

with the defined active layer of 0.12 cm2. cthermal annealing at 50 oC for 10 min. dthe values in parentheses are average values obtained from 10 devices.

Figure 6. AFM height images (top) and phase images (below) of the thin films: (a, d) pristine PBDB-T:DTCCIC-C17 (1:1.5 in wt%) blend; (b, e) 0.5 v% DIO-treated PBDB-T:DTCCIC-C17 (1:1.5 in wt%) blend; (c, f) 0.5 v% DIO-treated PBDB-T:DTCCIC-C17 blend (1:1.5 in wt%) with thermal annealing at 50 oC for 10 min. Atomic force microscopy (AFM) measurements (Figure 6) were used to investigate the morphology of the thin films. The pristine PBDB-T:DTCCIC-C17 blend film, 0.5 v% DIO-treated PBDB-T:DTCCIC-C17 blend and 0.5 v% DIO-treated and thermally annealed (at 50 oC for 10 min) PBDB-T:DTCCIC-C17 blend all showed rather smooth surface. The root-mean-square (RMS) roughness of the pristine PBDB-T:DTCCIC-C17 blend film is 2.16 nm. After adding 0.5 v% DIO, the RMS roughness slightly increases to 2.27 nm, which might stem from the formation of the better nanoscale phase separation. As a result, the Jsc value of the device also increases from 12.70 mA cm-2 to 14.03 mA cm-2. When the ACS Paragon Plus Environment


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DIO-treated thin film was further thermally annealed, the RMS roughness maintains the same value of 2.27 nm and the Jsc value only marginally increases to 14.27 mA cm-2.

Conclusion In summary, a heptacyclic carbazole-based (DTCC) ladder-type A-LD-A-type DTCCIC-C17 is designed and synthesized. By side-chain molecular engineering, DTCCIC-C17 substituted with a bulkier branched 1-octylnonayl group shows a higher-lying LUMO energy level, more amorphous character, and excellent solution processability. The inverted device using the binary PBDB-T:DTCCIC-C17 blend with suitable energy alignments and complimentary absorption has achieved a superior efficiency of 9.48%.

Experimental section Fabrication and Characterization of OPV Devices. The photovoltaic devices were fabricated by the following procedures: The ITO-ZnO layer was prepared according to the previous report.53 The chlorobenzene solutions of PBDB-T:DTCCIC-C17 with an optimal weight ratio of 1:1.5 in wt % with or without 0.5 v% DIO as additive were heated at 65 °C and spin-coated (1600 rpm for 30 s) on top of the ZnO/ITO substrate. The thickness of pristine film and DIO-treated film is roughly 50 nm and 150 nm, respectively. Some samples were further thermally annealed at 50 °C for 10 min in the glove box. Finally, the MoO3 layer (7 nm) and silver anode (100 nm) were deposited by thermal evaporation at a pressure below 10-6 torr. The devices without encapsulation were characterized in ambient condition. Synthesis of 3: A Grignard reagent of (4-octylphenyl) magnesium bromide (5.6 mmol) was added to a solution of 1 (400 mg, 0.56 mmol) in anhydrous THF (10 mL) under nitrogen atmosphere, and then the mixture was refluxed 24 h. After cooling to room temperature, the mixture was quenched by MeOH, and extracted with ethyl acetate. The organic layer was washed with water, and then dried over anhydrous MgSO4. After removing solvent, the brown crude product 2 was obtained and used in the next step without further purification. To a mixture of 2 and acetic acid (15 mL) was refluxed under nitrogen for 2 h. After cooling to room temperature, the mixture was poured into ice water, neutralized with NaOH (aq), and then extracted with ethyl acetate. The organic layer was washed with water, and then dried over anhydrous MgSO4, After removing solvent, the residue was purified by column chromatography on silica gel using ACS Paragon Plus Environment

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n-hexane as eluent to give DTCC as orange solid (397 mg, 52% in two steps). 1H NMR (400 MHz, CDCl3): δ 7.85 (d, J = 14.4 Hz, 2H), 7.52 (br, 1H), 7.38 (br, 1H), 7.27 (d, J = 4.8 Hz, 2H), 7.19 (d, J = 8.0 Hz, 8H), 7.04-7.02 (m, 8H), 4.58 (m, 1H), 2.53 (t, J = 7.8 Hz, 8H), 2.33-2.27 (m, 2H), 2.01-1.95 (m, 2H), 1.29-1.11 (m, 72H), 0.87 (t, J = 6.6 Hz, 12H), 0.79 (t, J = 6.6 Hz, 6H); 13C NMR (400 MHz, CDCl3): δ156.36, 144.95, 143.05, 143.02, 142.18, 141.78, 141.72, 141.02, 138.61, 135.10, 134.65, 128.17, 127.90, 127.14, 123.32, 122.36, 120.93, 117.83, 117.47, 102.11, 99.50, 62.20, 56.78, 35.57, 33.78, 31.89, 31.75, 31.37, 29.71, 29.63, 29.59, 29.49, 29.46, 29.32, 29.24, 29.19, 26.98, 22.67, 22.58, 14.11, 14.04 (Multiple carbon peaks result from phenomenon of atropisomerism); HRMS (FAB) Calcd for C95H127NS2 [M]+, 1345.9405; found, 1345.9406. Synthesis of 4: A mixture of DTCC (3) (300 mg, 0.22 mmol) and 1,2-dichloroethane (15 mL) was deoxygenated with nitrogen for 30 min and then added by POCl3 (0.10 mL) in DMF (1.5 mL) at 0 oC. After being stirred at 60 oC for 20 h, the mixture was poured into Na2CO3 (aq) and extracted with CH2Cl2. The organic layer was washed with water, and then dried over anhydrous MgSO4. After removal of the solvent, the residue was purified by column chromatography on silica gel using n-hexane/CH2Cl2 (1:1) as eluent to give 4 as a yellow solid (206 mg, 66%).1H NMR (400 MHz, CDCl3): δ 9.86 (s, 2H), 7.93 (d, J = 13.6 Hz, 2H), 7.69 (br, 3H), 7.57 (br, 1H), 7.18 (d, J = 8.4 Hz, 8H), 7.07 (d, J = 8.4 Hz, 8H), 4.64 (m, 1H), 2.56 (t, J = 7.6 Hz, 8H), 2.34-2.31 (m, 2H), 2.07-2.01 (m, 2H), 1.30-1.07 (m, 72H), 0.88 (t, J = 6.8 Hz, 12H), 0.79 (t, J = 7.0 Hz, 6H);

13

C NMR (400MHz, CDCl3): δ 182.80, 156.86, 151.76, 151.72, 145.97, 145.55, 142.75,

141.84, 141.69, 139.19, 134.08, 133.67, 132.37, 128.43, 127.69, 124.23, 122.83, 118.38, 118.03, 103.90, 101.40, 62.37, 57.19, 35.52, 33.73, 31.86, 31.84, 31.69, 31.33, 29.55, 29.43, 29.26, 29.20, 29.11, 26.91, 22.64, 22.63, 22.53, 14.09, 14.07, 14.01, 13.99 (Multiple carbon peaks result from phenomenon of atropisomerism); HRMS (FAB) Calcd for C97H127NO2S2 [M]+, 1401.9303; found, 1401.9281. Synthesis

of

DTCCIC-C17:

A

mixture

of

4

(150

mg,

0.11

mmol),

2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (163 mg, 0.84 mmol) in CHCl3 (25 mL) was deoxygenated with nitrogen for 30 min and then pyridine (1 mL) was added and refluxed for 24 h. After the mixture was cooled to room temperature, the mixture was poured into water (100 mL) and extracted with CH2Cl2. The organic layer was washed with water, and then dried over anhydrous MgSO4. After removal of the solvent, the residue was purified by column chromatography on silica gel using n-hexane/CH2Cl2 (1:1) ACS Paragon Plus Environment


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as eluent to give DTCCIC-C17 as a dark blue solid (167 mg, 89%). 1H NMR (400 MHz, CDCl3): δ 8.93 (d, J = 4.8 Hz, 2H), 8.71-8.69 (m, 2H), 7.95-7.92 (m, 4H), 7.85 (br, 1H), 7.78-7.70 (m, 8H), 7.18 (d, J = 8.4 Hz, 8H), 7.08 (d, J = 8.4 Hz, 8H), 4.61 (m, 1H), 2.55 (t, J = 7.8 Hz, 8H), 2.34-2.30 (m, 2H), 2.12-2.06 (m, 2H), 1.29-1.11 (m, 72H), 0.86 (t, J = 6.8 Hz, 12H), 0.78 (t, J = 6.8 Hz, 6H);

13

C NMR (400MHz, CDCl3): δ

188.64, 188.48, 161.05, 160.97, 160.52, 160.46, 157.99, 147.17, 143.37, 141.91, 141.53, 141.48, 140.64, 139.98, 139.89, 139.84, 138.68, 138.60, 136.90, 135.03, 134.58, 134.35, 134.12, 128.55, 128.35, 127.73, 125.64, 125.29, 124.24, 123.64, 121.56, 121.48, 118.74, 118.40, 114.73, 104.79, 102.24, 77.20, 68.75, 68.70, 62.40, 62.36, 57.49, 35.54, 33.62, 31.86, 31.72, 31.34, 29.68, 29.44, 29.43, 29.36, 29.30, 29.20, 29.11, 27.09, 22.64, 22.56, 14.08, 14.02 (Multiple carbon peaks result from phenomenon of atropisomerism); HRMS (FAB) Calcd for C121H135N5O2S2 [M]+, 1754.0052; found, 1754.0044.

Supporting Information. TGA, DSC measurements, device optimization parameters, computational details, and NMR spectra.

Acknowledgment We thank the Ministry of Science and Technology and the Ministry of Education, 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.

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Graphical abstract


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A Haptacyclic Carbazole-Based Ladder-Type Non-Fullerene Acceptor

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