WO2018068725A1

WO2018068725A1 - Difluorobenze-based building blocks and conjugated polymers

Info

Publication number: WO2018068725A1
Application number: PCT/CN2017/105684
Authority: WO
Inventors: He Yan; Zhengke LI
Original assignee: He Yan; Li Zhengke
Priority date: 2016-10-11
Filing date: 2017-10-11
Publication date: 2018-04-19

Abstract

Disclosed are donor-acceptor conjugated polymers, methods for their preparation and intermediates used therein. The conjugated polymer contains chemical structure with difluorobenze-based building blocks.

Description

DIFLUOROBENZE-BASED BUILDING BLOCKS AND CONJUGATED POLYMERS

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 62/496,212 filed on 11 Oct. 2016 and entitled “DIFLUOROBENZE-BASED CONJUGATED POLYMERS FOR ELECTRONIC AND PHOTONIC APPLICATIONS” ， which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to novel donor-acceptor conjugated polymers, methods for their preparation and intermediates used therein, the use of formulations containing such polymers as semiconductors in organic photovoltaic (OPV) or other organic electronics (OE) , and to OE and OPV devices made from these formulations.

BACKGROUND

The organic solar cell (OSC) is considered a promising low-cost and environmentally friendly solar technology, as it can be produced using low-cost printing methods and does not contain any toxic components.

A typical OSC device consists of a pair of matching materials that function as electron donor and acceptor, respectively. For the acceptor, fullerene derivatives have been the dominant choice of materials for nearly two decades and best-efficiency (over 10％) OSCs can only be achieved using fullerene acceptors. However, fullerenes exhibit many drawbacks such as high production cost and poor absorption properties.

To overcome these drawbacks, the OSC community has been actively exploring non-fullerene OSCs, which are believed to be the next generation of OSCs that will be more efficient and stable and lower in cost than conventional fullerene devices. There are several material options to construct non-fullerene OSCs. Among them, OSCs based on a polymer donor and a small molecular acceptor (SMA) have seen rapid development in the past two years. To develop efficient polymer: SMA OSCs, intensive research efforts have been devoted to the design and synthesis of novel SMA materials, which then are typically combined with known donor polymers (for example, PTB7-Th) to construct polymer: SMA OSCs.

However, these known donor polymers were mainly designed for polymer: fullerene OSCs. Although they match well with fullerene acceptors and enable high-efficiency fullerene devices, they may not be the best matching donors for SMA materials.

To achieve efficient OSCs, the donor polymer plays a critical role in controlling the bulk-heterojunction (BHJ) morphology of OSCs. One successful approach of achieving a favorable morphology (containing highly crystalline and small domains) in fullerene OSCs is the use of a family of donor polymers with strong temperature dependent aggregation (TDA) properties, which yielded multiple cases of high-efficiency (higher than 10％) polymer: fullerene OSCs. The crystallinity of these TDA polymers were much greater than conventional PTB7-family polymers. The key property is the strong TDA behavior of polymers, which leads to well-controlled aggregation of the polymer during the film cooling and drying process, resulting in highly crystalline yet small domains (20 nm) at the same time.

However, we found that the state-of-the-art TDA polymers do not perform with in SMA OSCs. For example, while PffBT4T-2OD yielded 10.9％fullerene cells, it only produced lower than 4％devices with SMAs. The successful polymer design rationales for fullerene OSCs do not appear to work best for non-fullerene OSCs and a different polymer design rationale is needed.

SUMMARY

In this invention, we develop novel building blocks and conjugated polymers based on difluorinated benzene unit. Inserting a benzene ring into polymer backbone is usually believed to be harmful to the device performance of polymers, and there are few report of polymers based on benzene building block that can achieve excellent device performances. It is believed that due to the large twisting angle between benzene and thiophene, polymers containing benzene ring cannot form a planar structure and thus of lower mobility, which is harmful for device performances.

There are significant twisting between benzene and thiophene units

However, it was surprising found in the present invention that when the benzene unit is substituted with two fluorine atoms, the twisting angle between the difluorobenzene unit and the neighboring thiophene units can be reduced. As a result, a near co-planar structure can be formed, which is beneficial for OPV performance.

In some embodiments, we developed difluorobenzene building blocks (named FB-O, T-FB-T-O) and related donor polymers (named PTFB-O, PBTFB-DT) that enable highly efficient non-fullerene OSCs with PCEs up to 10.9％, which is near the best PCEs achievable for fullerene or non-fullerene OSCs to date. Interestingly, this donor polymer does not yield high-efficiency OSCs when combined with fullerene acceptors, the PCE of which is only 6.5％.

Another polymer (PBTFB-DT) based on this building block is also developed, and the PCE of which is 8.9％. The excellent OSCs device performance of these polymers indicate the difluorobenzene building block is promising for developing polymers in the field of photovoltaics.

In many embodiments, the T-FB-T-O building block can be used to construct many novel conjugated polymers.

In some other embodiments, another difluorobenzene building block, T-FB-T-P, can also be used to construct conjugated polymers for OPV devices, with high efficiency.

The formulations, methods and devices of the present invention (diflurobenzene building block) provide surprising improvements in the efficiency of the OE devices and the production thereof. Unexpectedly, the performance, the lifetime and the efficiency of the OE devices can be improved, if these devices are achieved by using a formulation of the present subject matter. Furthermore, the formulation of the present subject matter provides an astonishingly high level of film forming. Especially, the homogeneity and the quality of the films can be improved. In addition thereto, the present subject matter enables better solution printing of OE devices, especially OPV devices.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the drawings described above or below are for illustration purposes only. The drawings are not necessarily to scale, with emphasis generally being placed upon illustrating the principles of the present teachings. The drawings are not intended to limit the scope of the present teachings in any way.

FIG. 1 shows the solar cell characterization of bulk heterojunction devices prepared from Polymer: SMA. (a) current-voltage plots under illumination with AM 1.5G solar simulated light at 100 mW cm^-2. (b) EQE spectra of the BHJ solar cells with SMA.

FIG. 2 shows optical characterization of PTFB-O and PTFB-P. (a) UV-Vis absorption coefficients in solution； (b) comparison of the optical absorbance of pure films normalized by thickness

FIG. 3 shows UV-Vis absorption spectra evolutions of polymers. (a) PTFB-P and (b) PTFB-O in dichlorobenzene solution. (Cooling process, from 100 ℃ to 10 ℃. )

FIG. 4 shows two-dimensional (2D) GIWAXS pattern of pure polymer and polymer blend films. (a) PTFB-O, (b) PTFB-P, (c) PTFB-O: ITIC, (d) PTFB-P: ITIC, (e) PTFB-O: PC₇₁BM, (f) PTFB-P: PC₇₁BM.

DETAILED DESCRIPTION

In a first embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

In one example of this embodiment, the conjugated polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.

In another example of this embodiment, the conjugated polymer were found to exhibit temperature dependent aggregation properties, characterized in that the absorption onset of the polymer solution exhibits a red shift of at least 50 nm when the solution is cooled from 140 ℃ to room temperature.

In a second embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.

wherein R is selected from H and straight or branched hydrocarbon group；

In a third embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

wherein R is branched hydrocarbon group；

In one example of this embodiment, Ar is selected from:

Z₁, Z₂, Z₃, Z₄, Z₅, Z₆ are S, O, or Se；

X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈ is H, F, or Cl；

R, R₃, R₄ are independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 2-40 C atoms, wherein one or more non-adjacent C atoms are optically replaced by -O-, -S-, -C (O) -, -C (O-) -O-, -O-C (O) -, -O-C (O) -O-, - CR⁰＝CR⁰⁰-, or -C≡C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryoxy, heteroaryloxy, arycarbonyl, heteroarycarbonyl, arycarbonyloxy, heteroarylcarbonyloxy, aryxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms unsubstituted or substituted by one or more non-aromatic groups, wherein R⁰ and R⁰⁰ are independently a straight-chain, branched, or cyclic alkyl group；

In a fourth embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.

In another example of this embodiment, the conjugated polymer comprises one or more repeating units of the following formula:

wherein R is selected from H, and straight or branched hydrocarbon groups.

In still another example of this embodiment, the conjugated polymer were found to exhibit temperature dependent aggregation properties, characterized in that the absorption onset of the polymer solution exhibits a red shift of at least 50 nm when the solution is cooled from 140 ℃ to room temperature.

In a fifth embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

wherein R is selected from H and straight or branched hydrocarbon group；

In a sixth embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer comprising one or more repeating units of the following formula:

wherein R is straight or branched hydrocarbon group；

wherein R is branched hydrocarbon group；

Ar is selected from:

Z₁, Z₂, Z₃, Z₄, Z₅, Z₆ are S, O, or Se；

X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈ is H, F, or Cl；

R, R₃, R₄ are independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 2-40 C atoms, wherein one or more non-adjacent C atoms are optically replaced by -O-, -S-, -C (O) -, -C (O-) -O-, -O-C (O) -, -O-C (O) -O-, -CR⁰＝CR⁰⁰-, or -C≡C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryoxy, heteroaryloxy, arycarbonyl, heteroarycarbonyl, arycarbonyloxy, heteroarylcarbonyloxy, aryxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms unsubstituted or substituted by one or more non-aromatic groups, wherein R⁰ and R⁰⁰ are independently a straight-chain, branched, or cyclic alkyl group；

In some embodiments, Ar is selected from:

wherein X can be independently selected from H or F, and R, R2 can be selected from straight-chain or branched saturated hydrocarbon group.

In a seventh embodiment of the present invention, an organic photovoltaic (OPV) device is disclosed. The OPV contains conjugated polymers comprising one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.

wherein R is selected from H, and straight or branched hydrocarbon groups.

EXAMPLES

Example 1 -Synthesis of monomers

1, 4-di (thiophen-2-yl) benzene (S2a) . To a 50 mL tube were added S1a (472 mg, 2.0 mmol) , tributyl (thiophen-2-yl) stannane (1.87 g, 5.0 mmol) , Pd₂ (dba) ₃ (91.5 mg, 0.1 mmol) , P- (o-tol) ₃ (182 mg, 0.6 mmol) and Toluene. The mixture was then put into microwave reactor and heated at 110 ℃ for 1h. After cooled to room temperature, the reaction mixture was filtered, diluted with chloroform and washed with brine 3 times. The organic layer was dried over Na₂SO₄, filtered and concentrated. Then the residue was recrystallized from isopropanol to yield pure product S2a as a light yellow solid (308 mg, 64％yield) . ¹H NMR (400 MHz, CDCl₃) δ 7.62 (s， 4H) ， 7.34 (d， J ＝ 3.6 Hz, 2H) , 7.29 (d, J ＝ 5.1 Hz, 2H) , 7.11 -7.07 (m, 2H) . ¹³C NMR (101 MHz, CDCl₃) δ 143.90， 133.48， 128.10, 126.29, 124.90, 123.10. HRMS (MALDI+) Calcd for C₁₄H₁₀S₂ (M ⁺) : 242.0224, Found: 242.0230.

2, 2'- (2, 5-difluoro-1, 4-8phenylene) dithiophene (S2b) . Synthesis of S2b was carried out in a similar manner to that of S2a using S1b (544 mg, 2.0 mmol) , tributyl (thiophen-2-yl) stannane (1.87 g, 5.0 mmol) , Pd₂ (dba) ₃ (91.5 mg, 0.1 mmol) , P- (o-tol) ₃ (182 mg, 0.6 mmol) and Toluene. . (406 mg, 73％yield) . ¹H NMR (400 MHz, CDCl₃) δ 7.52 (d， J ＝ 3.6 Hz, 2H) , 7.40 (d, J ＝ 5.1 Hz, 2H) , 7.37 (d, J ＝ 4.0 Hz, 2H) , 7.17 -7.11 (m, 2H) . ¹⁹F NMR (376 MHz, CDCl₃) δ -139.10 (s) . ¹³C NMR (101 MHz, CDCl₃) δ 148.02 (dd, J ＝ 253.0, 15.9 Hz) , 135.88 (s) , 127.96 (s) , 126.89 (t, J ＝ 3.2 Hz) , 126.39 (s) , 122.80 (t, J ＝ 3.6 Hz) , 122.67 -122.44 (m) . HRMS (MALDI+) Calcd for C₁₄H₈F₂S₂ (M ⁺) : 278.0035, Found: 278.0031.

2, 2'- (2, 3-difluoro-1, 4-phenylene) dithiophene (S2c) . Synthesis of S2c was carried out in a similar manner to that of S2b. (420 mg, 76％yield) . ¹H NMR (400 MHz, CDCl₃) δ 7.51 (d， J ＝ 3.6 Hz, 2H) , 7.41 (m, 4H) , 7.16 -7.11 (m, 2H) . ¹⁹F NMR (376 MHz, CDCl₃) δ -119.17 (t, J ＝ 9.1 Hz) . ¹³C NMR (101 MHz, CDCl₃) δ 154.87 (dd， J ＝247.5, 3.3 Hz) , 135.79 (s) , 127.89 (s) , 126.86 (t, J ＝ 3.2 Hz) , 126.54 (t, J ＝ 1.8 Hz) , 122.25 -121.55 (m) , 115.38 (dd, J ＝ 19.4, 12.1 Hz) . HRMS (MALDI+) Calcd for C₁₄H₈F₂S₂ (M ⁺) : 278.0035, Found: 278.0038.

1, 4-bis (5- (trimethylstannyl) thiophen-2-yl) benzene (S3a) To a solution of S2a (242 mg, 1.0 mmol) in 20 mL fresh distilled anhydrous THF was added 1.6 M n-BuLi in hexane (1.38mL, 2.2 mmol) dropwise at -78 ℃ under N₂. The mixture was warmed and stirred at 0 ℃ for 1h. 1.0 M Me₃SnCl in hexane (2.5mL, 2.5 mmol) was then added in one portion at -78 ℃ and the reaction mixture was warmed to room temperature and stirred overnight. The resulted solution was then extracted by ethyl acetate 3 times. The organic layer was combined and washed with brine 3 times. The organic layer was dried over Na₂SO₄, filtered and concentrated. Then the residue was recrystallized from isopropanol to yield pure product S3a as a light green solid (402 mg, 71％yield) . ¹H NMR (400 MHz, CDCl₃) δ 7.61 (s， 4H) ， 7.43 (d， J ＝ 3.3 Hz, 2H) , 7.17 (d, J ＝ 3.4 Hz, 2H) , 0.50 -0.30 (m, 18H) . ¹³C NMR (101 MHz, CDCl₃) δ 149.71 (s) ， 137.70 (s) ， 136.24 (s) , 133.33 (s) , 126.23 (s) , 124.23 (s) , -8.23 (s) . HRMS (MALDI+) Calcd for C₂₀H₂₆S₂Sn₂ (M ⁺) : 568.9520, Found: 568.9537.

( (2, 5-difluoro-1, 4-phenylene) bis (thiophene-5, 2-diyl) ) bis (trimethylstannane) (S3b) . Synthesis of S3b was carried out in a similar manner to that of S3a using S2b (278 mg, 1.0 mmol) , 1.6 M n-BuLi in hexane (1.38mL, 2.2 mmol) and Me₃SnCl (2.5mL, 2.5 mmol) . S3b was yielded as a light yellow solid (486 mg, 81％yield) . ¹H NMR (400 MHz, CDCl₃) δ 7.62 (d， J ＝ 3.2 Hz, 2H) , 7.39 (d, J ＝ 3.9 Hz, 2H) , 7.22 (d, J ＝ 3.4 Hz, 2H) , 0.50 -0.33 (m, 18H) . ¹⁹F NMR (376 MHz, CDCl₃) δ -139.08 (d, J ＝ 7.4 Hz) . ¹³C NMR (101 MHz, CDCl₃) δ 147.75 (dd， J ＝ 252.6, 15.9 Hz) , 141.59 (s) , 139.52 (s) , 136.02 (s) , 127.83 (s) , 122.84 (s) , 122.44 (s) , -8.20 (s) . HRMS (MALDI+) Calcd for C₂₀H₂₄F₂S₂Sn₂ (M ⁺) : 605.9331, Found: 605.9329

( (2, 3-difluoro-1, 4-phenylene) bis (thiophene-5, 2-diyl) ) bis (trimethylstannane) (S3c) . Synthesis of S3c was carried out in a similar manner to that of S3b. S3c was yielded as a colorless solid (443 mg, 73％yield) ¹H NMR (400 MHz, CDCl₃) δ 7.60 (d， J ＝ 3.2 Hz, 2H) , 7.40 (t, J ＝ 9.1 Hz, 2H) , 7.21 (m, 2H) , 0.62 -0.27 (m, 18H) . ¹⁹F NMR (376 MHz, CDCl₃) δ -119.11 (m) . ¹³C NMR (101 MHz, CDCl₃) δ 154.61 (dd， J ＝ 247.1, 3.2 Hz) , 141.48 (s) , 139.70 (s) , 136.71 -135.42 (m) , 127.76 (t, J ＝ 3.0 Hz) , 122.21 -121.44 (m) , 115.27 (dd, J ＝ 19.3, 12.2 Hz) , -8.16 (s) . HRMS (MALDI+) Calcd for C₂₀H₂₄F₂S₂Sn₂ (M ⁺) : 605.9331, Found: 605.9328.

Example 2 -Synthesis of polymers

Synthesis of PTB. To a 10 mL Microwave vial equipped with stir bar, S4 (23.8mg, 0.02 mmol) , S3a (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chloroform. After cooled to room temperature, the chloroform portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark red solid. (16.7mg, 66 ％yield) : GPC: Mn: 36.2 kDa, Mw: 71.4 kDa； PDI＝1.97.¹H NMR (400 MHz, CDCl₃) δ 8.19 (s， 2H) , 7.71 (s, 4H) , 7.39 (s, 2H) , 7.29 (s, 2H) , 4.83 (s, 2H) , 2.92 (s, 4H) , 2.30 (s, 2H) , 1.89 (s, 2H) , 1.65 -1.05 (m, 77H) , 0.91 (s, 12H) . Anal. Calcd for C₆₅H₉₃F₄N₃S₄: C, 74.54； H, 9.11； N, 3.30. Found: C, 74.24； H, 9.08； N, 3.20.

Synthesis of PTFB-O. To a 10 mL Microwave vial equipped with stir bar, S4 (23.8mg, 0.02 mmol) , S3b (12.1mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone, chloroform and toluene. After cooled to room temperature, the toluene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark red solid. (15.0 mg, 57 ％yield) : GPC: Mn: 43.8 kDa, Mw: 88.4 kDa； PDI＝2.02.¹H NMR (400 MHz, CDCl₃) δ 8.20 (s， 2H) ， 7.57 (s， 2H) ， 7.49 (s， 2H) ， 7.34 (s， 2H) ， 4.84 (s， 2H) ， 3.49 (s， 2H) ， 2.93 (s， 4H) , 2.31 (s, 2H) , 1.90 (s, 2H) , 1.37 (d, J ＝ 54.1 Hz, 74H) , 1.18 (s, 3H) , 0.92 (s, 12H) . Anal. Calcd for C₆₅H₉₃F₄N₃S₄: C, 72.49； H, 8.70； N, 3.21. Found: C, 72.22； H, 8.90； N, 3.20.

Synthesis of PTFB-P. To a 10 mL Microwave vial equipped with stir bar, S4 (23.8mg, 0.02 mmol) , S3c (12.1mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and oroform. After cooled to room temperature, the toluene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark red solid. (18.3 mg, 70 ％yield) : GPC: Mn: 46.1 kDa, Mw: 75.8 kDa； PDI＝1.64.¹H NMR (400 MHz, CDCl₃) δ 8.20 (s， 2H) ， 7.53 (s， 4H) ， 7.33 (s, 2H) , 4.82 (s, 2H) , 2.92 (s, 4H) , 2.29 (s, 2H) , 1.89 (s, 2H) , 1.36 (d, J ＝ 44.3 Hz, 74H) , 1.17 (s, 3H) , 0.91 (s, 12H) . Anal. Calcd for C₆₅H₉₃F₄N₃S₄: C, 72.49； H, 8.70； N, 3.21. Found: C, 72.53； H, 8.81； N, 3.13.

Synthesis of P1

To a 10 mL Microwave vial equipped with stir bar, S5 (22.3mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark green solid. (14.1mg, 54.6 ％yield. )

Synthesis of P 2

To a 10 mL Microwave vial equipped with stir bar, S6 (27.0mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark blue solid. (20.8mg, 66.0％yield)

Synthesis of P3

To a 10 mL Microwave vial equipped with stir bar, S7 (27.0mg, 0.02 mmol) , S3b (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark blue solid. (22.4mg, 71.1％yield)

Synthesis of P4

To a 10 mL Microwave vial equipped with stir bar, S8 (24.0mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chloroform. After cooled to room temperature, the chloroform portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark green solid. (18.0mg, 67％yield)

Synthesis of P5

To a 10 mL Microwave vial equipped with stir bar, S9 (23.0mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark green solid. (21.5mg, 74.1 ％yield)

Synthesis of P6

To a 10 mL Microwave vial equipped with stir bar, S10 (23.7mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark purple solid. (17.5mg, 65.8 ％yield)

Synthesis of P7

To a 10 mL Microwave vial equipped with stir bar, S10 (23.7mg, 0.02 mmol) , S3b (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark purple solid. (18.6mg, 69.9 ％yield)

Synthesis of P8

To a 10 mL Microwave vial equipped with stir bar, S11 (31.4mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark purple solid. (24.5mg, 71.5 ％yield)

Synthesis of P9

To a 10 mL Microwave vial equipped with stir bar, S11 (31.4mg, 0.02 mmol) , S3b (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark purple solid. (23.1mg, 67.2 ％yield)

Synthesis of P10

To a 10 mL Microwave vial equipped with stir bar, S12 (32.9mg, 0.02 mmol) , S3b (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark green solid. (24.8mg, 69.1 ％yield)

Synthesis of P11

To a 10 mL Microwave vial equipped with stir bar, S12 (32.9mg, 0.02 mmol) , S3c (11.4mg, 0.02 mmol) , Pd₂ (dba) ₃ (0.3 mg) and P (o-tol) ₃ (0.6 mg) were added. After transferred to glove box and 0.3 mL chlorobenzene added, the vial was sealed and heated at 140 ℃ for 24h. Then the product was diluted with chlorobenzene and precipitated in methanol. The resulting solids were subsequently subjected to Soxhlet extraction with acetone and chlorobenzene. After cooled to room temperature, the chlorobenzene portion was concentrated, precipitated in methanol, collected by filtration and dried in vacuo to get the polymer as dark green solid. (20.7mg, 57.7 ％yield)

Example 3 -Characterization of Polymers

Example 3a: Optical properties

Film UV-Vis absorption spectra of polymers from Example 2 were acquired on a Perkin Elmer Lambda 20 UV/VIS Spectrophotometer. All film samples were spin-cast on ITO/ZnO substrates. Solution UV-Vis absorption spectra at elevated temperatures were collected on a Perkin Elmer Lambda 950 UV/VIS/NIR Spectrophotometer. The temperature of the cuvette was controlled with a Perkin Elmer PTP 6+6 Peltier System, which is supplied by a Perkin Elmer PCB 1500 Water Peltier System. Before each measurement, the system was held for at least 10 min at the target temperature to reach thermal equilibrium. A cuvette with a stopper (Sigma Z600628) was used to avoid volatilization during the measurement. The onset of the absorption is used to estimate the polymer bandgap.

Example 3b: Electronic properties

Cyclic voltammetry was carried out on a CHI760E electrochemical workstation with three electrodes configuration, using Ag/AgCl as the reference electrode, a Pt plate as the counter electrode, and a glassy carbon as the working electrode. Polymers were drop-cast onto the electrode from DCB solutions to form thin films. 0.1 mol L^-1 tetrabutylammonium hexafluorophosphate in anhydrous acetonitrile was used as the supporting electrolyte. Potentials were referenced to the ferrocenium/ferrocene couple by using ferrocene as external standards in acetonitrile solutions. The scan rate is 0.1 V s^- ¹.

Example 4 -Device Fabrication

Pre-patterned ITO-coated glass with a sheet resistance of about 15Ω per square was used as the substrate. It was cleaned by sequential sonications in soap DI water, DI water, acetone and isopropanol for 30 min at each step. After ultraviolet/ozone treatment for 60 min, a ZnO electron transport layer was prepared by spin coating at 5,000 r.p.m. from a ZnO precursor solution (diethyl zinc) . Active layer solutions (D/A ratio 1: 1.5 by weight) were prepared in CB. To completely dissolve the polymer, the active layer solution should be stirred on a hot plate at 100 ℃ for at least 3 h. Before spin coating, both the polymer solution and ITO substrate are preheated on a hot plate at about 110 ℃. Active layers were spin coated from the warm polymer solution on the preheated substrate in a N₂ glovebox at 1500 to 1800 r.p.m. to obtain thicknesses of about 100 nm. The polymer: SMA films were then annealed at 90 ℃ for 5 min before being transferred to the vacuum chamber of a thermal evaporator inside the same glovebox. At a vacuum level of 3 × 10^-6 Torr, a thin layer (20 nm) of MoO₃ or V₂O₅ was deposited as the anode interlayer, followed by deposition of 100 nm of Al as the top electrode. All cells were encapsulated using epoxy inside the glovebox. Device J-V characteristics was measured under AM1.5G (100 mW cm^-2) using a Newport solar simulator (94021A, a Xenon lamp with an AM1.5G filter) in air at room temperature. The light intensity was calibrated using a standard Si diode as a reference cell to bring spectral mismatch to unity. J-V characteristics were recorded using a Keithley 2400 source meter unit. Typical cells have devices area of 5.9 mm², which is defined by a metal mask with an aperture aligned with the device area. EQEs were characterized using a Newport EQE system equipped with a standard Si diode. Monochromatic light was generated from a Newport 300W lamp source.

Example 5 -Device Performance

The performance of OSCs based on PTFB-O and PTFB-P combined with a SMA (named ITIC, Figure 1b) or fullerene acceptor are summarized in Table 1. When ITIC was combined with PTFB-O, an impressive PCE of 10.1％was obtained, while the combination of PTFB-P and ITIC only achieved a PCE of 7.9％ (Table 1, Figure 1) . However, when PTFB-O and PTFB-P were combined with PC₇₁BM, PTFB-P yielded much better performance than PTFB-O (Supplementary Figure 2) . It thus appears that PTFB-O is a much more superior donor polymer match for ITIC, while PTFB-P is a better donor match for fullerene acceptor. By further optimizing the small molecule, 10.9％cell can be achieved combining PTFB-O with ITIC-Th (Figure 1) , mainly due to higher Jsc, originating from the stronger absorption properties of ITIC-Th.

Table 1. Photovoltaic properties of solar cells based on polymer: PC71BM and SMA. The average values are from 30 devices.

Example 6 -Mophology Characterization

We characterize the pure PTFB-O and PTFB-P films by grazing incidence wide angle X-ray scattering (GIWAXS) and compare their polymer crystallinity. The GIWAXS 2D maps of pure PTFB-O and PTFB-P films are shown in Figure 4 and the (010) and (100) crystal size and d spacing data are summarized in Table 2. It is clear that PTFB-P exhibits exceptionally strong lamellar stacking as high order diffraction peaks of (100) , (200) , (300) and (400) are all clearly visible. In contrast, the PTFB-O film does not exhibit high order lamellar stacking peaks and the peak intensity is quite low. The lamellar stacking d-spacing is also much smaller for PTFB-P (2.2 nm) than for PTFB-O (2.5 nm) , which proves that the interdigitation of alkyl chains in the PTFB-P film is much stronger. In addition, both the (010) and (100) crystal sizes of PTFB-P polymer are significantly larger than those of PTFB-O. These GIWAXS results are in good agreement with the highly regioregular structure and parallel alkyl chain arrangement of PTFB-P.

To understand the performance difference of fullerene OSCs based on PTFB-O and PTFB-P, the blend films of PTFB-O: PC₇₁BM and PTFB-P: PC₇₁BM were also characterized by GIWAXS. For polymer: fullerene blend films, the high polymer crystallinity of PTFB-P is maintained, as the (010) and (100) coherence length of PTFB-P: fullerene are 7.7 and 26 nm, which are significantly larger than those of PTFB-O: PC₇₁BM blend. In addition, the (010) peak of PTFB-P: PC₇₁BM blend changed to a preferred face-on orientation, which should be beneficial for charge transport in the vertical direction across the electrodes. The hole mobilities of the blends were estimated using Space charge limited current (SCLC) methods to be about 1.7 × 10^-3 cm² V^-1 s^-1, and 4.7 × 10^-3 cm² V^-1 s^-1 for PTFB-O: PC₇₁BM and PTFB-P: PC₇₁BM respectively. Indeed, the high polymer crystallinity of PTFB-P leads to significantly higher hole mobility, which can explain the high FF of the OSCs based on PTFB-P: PC₇₁BM. These results are consistent with our previous reports showing that regioregular polymers typically exhibit stronger interdigitation and thus enhanced lamellar stacking and larger crystal size. These data explained the higher FF and efficiencies of PTFB-P than PTFB-O in fullerene based OSCs.

For non-fullerene OSCs based on SMA, PTFB-O: ITIC and PTFB-P: ITIC blends were also characterized by GIWAXS and soft X-ray scattering (SoXS) . Although the PTFB-P polymer is highly crystalline, GIWAXS data show that it cannot maintain its high crystallinity when blended with ITIC. As shown in Figure 4, the scattering intensity of PTFB-P: ITIC film is low and the (010) coherence length is reduced to only 3.4 nm. Integration of the scattering intensity of the (010) peaks of PTFB-P: ITIC and PTFB-O: ITIC films show that the scattering intensity of PTFB-P: ITIC is only 50％as much as that of PTFB-O: ITIC, which indicates that there is a significantly smaller volume fraction of crystalline domain for PTFB-P: ITIC. This result is also consistent with the hole mobility data of the two blends, which showed that the PTFB-O: ITIC blend exhibits a higher SCLC mobility of 4.4 × 10^-4 cm² V^-1 s^-1, versus 3.3 × 10^-4 cm² V^-1 s^-1 for PTFB-P: ITIC.

R-SoXS data revealed that the average domain size of PTFB-P: ITIC is about 50 nm, which is significantly larger than that of PTFB-O: ITIC. This result is also consistent with TEM and AFM images of the blend films, indicative of a significantly larger domain size for PTFB-P: ITIC. Considering that the commonly accepted optimal domain size for OSCs is about 20 ～ 30 nm, the excessively large domain size of the PTFB-P: ITIC should be one of the reasons that hurts the performance of PTFB-P: ITIC-based devices. The larger domain size of PTFB-P: PC₇₁BM could be due to the stronger π-π and lamellar stacking tendency of the PTFB-P polymer, which tend to stack into larger domains.

Table 2. Coherence length, d spacing and integration of peak intensity for pure polymer, polymer: SMA and polymer: PC₇₁BM films

Claims

A conjugated polymer comprising one or more repeating units of the following formula:
The conjugated polymer in claim 1, wherein the conjugated polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.
The conjugated polymer in claim 1, wherein the conjugated polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, and straight or branched hydrocarbon groups.
The conjugated polymer of claim 1, characterized in that the absorption onset of the polymer solution exhibits a red shift of at least 50 nm when the solution is cooled from 140 ℃ to room temperature.
The conjugated polymer of claim 1, wherein the conjugated polymer contains one or more repeating unit of the formula of:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.
The conjugated polymer of claim 1, wherein the polymer contains one or more repeating unit of formula of:

Wherein R is selected from H and straight or branched hydrocarbon group；

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.
The conjugated polymer of claim 1, wherein the polymer contains one or more repeating unit of formula selected from:

Wherein R is branched hydrocarbon group；

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.
The conjugated polymer of claim 1, wherein the polymer contains one or more repeating unit of formula selected from:

Wherein R is straight or branched hydrocarbon group；

Ar is selected from:

Z₁, Z₂, Z₃, Z₄, Z₅, Z₆ are S, O, or Se；

X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈ is H, F, or Cl；

R, R₃, R₄ are independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 2-40 C atoms, wherein one or more non-adjacent C atoms are optically replaced by -O-, -S-, -C (O) -, -C (O-) -O-, -O-C (O) -, -O-C (O) -O-, - CR⁰＝CR⁰⁰-, or -C≡C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryoxy, heteroaryloxy, arycarbonyl, heteroarycarbonyl, arycarbonyloxy, heteroarylcarbonyloxy, aryxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms unsubstituted or substituted by one or more non-aromatic groups, wherein R⁰ and R⁰⁰ are independently a straight-chain, branched, or cyclic alkyl group；
A conjugated polymer comprising one or more repeating units of the following formula:
The conjugated polymer in claim 10, wherein the polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.
The conjugated polymer in claim 10, wherein the polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, and straight or branched hydrocarbon groups.
The conjugated polymer of claim 10, characterized in that the absorption onset of the polymer solution exhibits a red shift of at least 50 nm when the solution is cooled from 140 ℃ to room temperature.
The conjugated polymer of claim 10, wherein the polymer contains one or more repeating unit of formula of:

Wherein R is selected from H and straight or branched hydrocarbon group；

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.
The conjugated polymer of claim 10, wherein the polymer contains one or more repeating unit of formula selected from:

Wherein R is straight or branched hydrocarbon group；

Ar is selected from the group consisting of unsubstituted or substituted monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar may contain one to five of said arylene or heteroarylene each of which may be fused or linked.
The conjugated polymer of claim 10, wherein the polymer contains one or more repeating unit of formula selected from:

Wherein R is branched hydrocarbon group；

Ar is selected from:

Z₁, Z₂, Z₃, Z₄, Z₅, Z₆ are S, O, or Se；

X₁, X₂, X₃, X₄, X₅, X₆, X₇, X₈ is H, F, or Cl；

R, R₃, R₄ are independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 2-40 C atoms, wherein one or more non-adjacent C atoms are optically replaced by -O-, -S-, -C (O) -, -C (O-) -O-, -O-C (O) -, -O-C (O) -O-, -CR⁰＝CR⁰⁰-, or -C≡C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryoxy, heteroaryloxy, arycarbonyl, heteroarycarbonyl, arycarbonyloxy, heteroarylcarbonyloxy, aryxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms unsubstituted or substituted by one or more non-aromatic groups, wherein R⁰ and R⁰⁰ are independently a straight-chain, branched, or cyclic alkyl group；
An organic photovoltaic (OPV) device that contains conjugated polymers comprising one or more repeating units of the following formula:
An organic solar cell device of claim 17, wherein the conjugated polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, F, and straight or branched hydrocarbon group；

X is S, O, or Se；

Y is N or C-H.
The conjugated polymer in claim 17, wherein the polymer comprises one or more repeating units of the following formula:

Wherein R is selected from H, and straight or branched hydrocarbon groups.
The conjugated polymer of claim 17, characterized in that the absorption onset of the polymer solution exhibits a red shift of at least 50 nm when the solution is cooled from 140 ℃ to room temperature.