WO2017223407A1 - Conjugated polymers containing alkyl and alkyl ester side chains - Google Patents

Abstract

The present invention is a conjugated polymer that contains both Unit (I) and Unit (II) is shown below: X, in each occurrence, is independently selected from S or Se. M₁ and M₂ are independently selected from H or F. R₁ and R₂ are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms. The number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 9: 1 to 1 :9.

Description

CONJUGATED POLYMERS CONTAINING ALKYL AND ALKYL ESTER SIDE CHAINS

CROSS REFERENCE TO RELATED APPLICATIONS

[1] This application claims priority to and the benefit of U.S. Provisional

Patent Application Ser. No. 62/493,141, filed on Jun. 24, 2016, the disclosure of which is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[2] The present subject matter relates to novel conjugated polymers, methods for their preparation and intermediates used therein, the use of such formulations as semiconductor in organic electronic (OE) devices, especially in organic solar cells (OSC) and organic field-effect transistor (OFET) devices, and to OE and OSC devices made from these formulations.

2. Description of the Related Art

[3] In recent years there has been growing interest in the use of organic semiconductors, including conjugated polymers, for various electronic applications such as organic solar cells (OSC). One particular area of importance is the field of organic solar cells. Organic semiconductors have found use in OSC as they allow devices to be manufactured by solution-processing techniques such as spin casting and printing. Solution processing can be carried out cheaper and on a larger scale compared to the evaporative techniques used to make inorganic thin film devices. State-of-the-art OSC cells consist of a blend film of a conjugated polymer and a fullerene derivative. To achieve efficient OSC devices, a rational design of high-performance donor polymers is critically important.

[4] To develop high-performance donor polymers, the most important consideration is that the donor polymer should exhibit an aggregation property such that the polymer can yield a favorable donor:acceptor blend morphology containing crystalline yet reasonably small domains (<20 nm).

[5] Recently, a new family of donor polymers with strong temperature-dependent-aggregation (TDA) property were developed that exhibit such a favorable aggregation property. These polymers are mostly disaggregated and easily soluble in solution at high temperatures, yet they can strongly aggregate in solution when it is cooled to room temperature. Utilizing this unique TDA property, the hot solutions of polymer:fullerene blends were processed. By controlling the processing temperature and other conditions (e.g., spin rates, concentration, etc.), the extent of polymer aggregation in solution and thus pi-pi stacking in the solid state can be effectively controlled, which leads to a favorable BHJ morphology containing highly crystalline and pure yet sufficiently small domains. This well-controlled and near-optimal BHJ morphology produced over a dozen cases of efficient OSCs with active layer near 300 nm thick yet that can still achieve high FFs (70-77%) and efficiencies (10-11.7%) . By studying the structure-property relationship of the donor polymers, we show the 2nd position branched alkyl chains and the fluorination on the polymer backbone are two key structural features that enable the TDA property.

[6] The key structural feature of these TDA polymers is the 2^nd position branched alkyl chains sitting between two thiophene units. Such 2^nd position branched alkyl chains enabled the strong TDA properties as shown in FIG. 7. The absorption peak of the polymer solution shift for more than 50 nm when the polymer solution is cooled from 120 °C to room temperature.

[7] Although rarely reported, it is also possible to attach alkyl ester side chains on a thiophene unit (as shown below) to construct donor polymers. However, it was found that the polymers with alkyl ester side chains do not exhibit the strong TDA properties. Therefore, it is much more challenging to construct a high-performance polymer with all alkyl ester side chains

[8] Nevertheless, ester side chains have some advantages, one of which is to tune the highest occupied molecular orbital HOMO and LUMO levels as the ester group has a strong electron withdrawing ability. Due to this reason, the alkyl ester group can enhance the Voc of the OSC devices.

[9] Lastly, it is important to note that, although fullerene derivatives have been the dominant choice of materials for nearly two decades, 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 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 developments 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 mamly 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

[10] To achieve efficient non-fullerene OSCs, the donor polymer plays a critical role in controlling the bulk-heterojunction (BHJ) morphology. 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, evidenced by their much larger (010) and (100) crystal size and higher hole mobility. 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, it was found that the state-of-the-art TDA polymers do not perform well in SMA OSCs. For example, while PffBT4T-20D yielded 10. 8% fullerene cells, it only produced lower than 4% devices with SMAs.

[11] With these, it is clear that donor polymers with all alkyl side chains do not work well for non-fullerene OSCs.

SUMMARY OF THE INVENTION

[12] In order to overcome the drawbacks of prior arts for polymers with all alkyl side chains and polymers with all alkyl ester side chains, the present invention provides various embodiments described below. [13] In one embodiment, it was surprisingly found that a polymer containing both the alkyl thiophene and alkyl ester thiophene units [shown below as Unit (I) and Unit (II)] can perform exceptionally well when combined with non-fullerene small molecular acceptors.

Unit (I) Unit (II)

[14] In other words, the polymer (with some alkyl side chains and some alkyl ester side chains on the beta positions of the thiophene units) surprisingly outperform the polymer with 100% of alkyl side chains and the polymer with 100% alkyl ester side chains. The combination use of alkyl and alkyl ester side chains yielded very surprising and beneficial results as shown below.

P3TEA, best efficiency 9.5%

PffBT4T-20D, best efficiency 3.2%

-PDI2 is the non-fullerene acceptor

[15] In another embodiment, it was found that polymers cotaining partially alkyl thiophene and partially alkyl ester thiophene units exhibit similar TDA properties (absorption peak shifts for more than 50 nm when the solution is cooled from 100°C for room temperature) as demonstrated for previous polymers, while the polymer with 100% alkyl ester thiophene do not exhibit such TDA properties, which is important for morphology control and reproducible produce of large-area solar cells.

P3TEA

[16] In another embodiment, it was surprising found that a terthiphene polymer with 50% of alkyl thiophene and 50% alkyl ester thiophene units exhibit unprecedentedly high Voc and efficiency that outperform the polymer with 100% alkyl side chains by a large margin, when the polymers were combined with PDI-based non-fullerene acceptors.

[17] In one embodiment of the invention, it was found that the introduction of the alkyl ester side chain on the beta position of the thiophene unit can enhance the crystallinity of the polymer, which may be favorable for OSC operation. However, it was also surprisingly found that the polymer with all its side chains being alkyl ester side chains does not possess the TDA property, an important property to control the morphology of OSCs.

[18] In another embodiment, it was surprisingly found that the polymer with 50% alkyl side chains and 50% alkyl ester side chains on the beta position of the thiophene units exhibit two attractive features at the same: 1) it exhibits the strong TDA properties, which is critical for morphology control; 2) it exhibits enhanced crystallinity compared to the polymer with 100% alkyl side chains.

[19] In another embodiment, it was surprisingly found that the polymer with 50% alkyl side chains and 50% alkyl ester side chains on the beta position of the thiophene units exhibit a near-perfect blend morphology with a small domain size of about 10 nm and high crystallinity at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

[20] 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.

[21] FIG.1A shows the Chemical structures of donor polymer P3TEA and SMA SF-PDI₂.

[22] FIG.1B shows the J-V curve of a P3TEA:SF-PDI₂-based solar cell. Inset: device parameters of the P3TEA:SF-PDl₂-based solar cell.

[23] FIG.1C shows the EQE curve of a P3TEA:SF-PDI₂-based solar cell.

[24] FIG.2 shows the UV absorption of the polymer P3TEA.

[25] FIG.3 shows the cyclic voltammetry curve of the polymer P3TEA in 0.1

M (n-Bu)4N+PF6- acetonitrile solution.

[26]FIG.4A is the AFM image (Ι μιη x Ιμιη, left) of P3TEA:SF-PDI₂-based blend film.

[27]FIG.4B shows the TEM image (right) of P3TEA:SF-PDI₂-based blend film.

[28]FIG.5 is GIWAXS profiles of the pure PffBT4T-20D(Y5), pure PffBT4T-E(G5), PffBT4T-20D:SF-PDI₂(Y5/Jsl), PffBT4T-E:SF-PDI₂(G5/Jsl), pure

PffBT3T-l,2(S26), pure P3TEA(G17), PffBT3T-l,2:SP-PDI₂(S26/Jsl), P3TEA:SP-PDI₂(G17/Jsl) films.

[29]FIG.6 shows R-SoXS profiles of the PffBT4T-20D:SF-PDI₂(Y5/Jsl),

PffBT4T-E:SF-PDI₂ G5/Jsl), PffBT3T-l ,2:SP-PDI₂(S26/Jsl) and

P3TEA:SP-PDI₂(G17/Jsl) four blend films.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[30] Formulations of the present teachings can exhibit semiconductor behavior such as optimized light absorption/charge separation in a photovoltaic device; charge transport/recombination/light emission in a light- emitting device; and/or high carrier mobility and/or good current modulation characteristics in a field-effect device. In addition, the present formulations can possess certain processing advantages such as solution-processability and/or good stability (e.g., air stability) in ambient conditions. The formulations of the present teachings can be used to prepare either p-type (donor or hole-transporting), n-type (acceptor or electron- transporting), or ambipolar semiconductor materials, which in turn can be used to fabricate various organic or hybrid optoelectronic articles, structures and devices, including organic photovoltaic devices and organic light-emitting transistors. [31] In the application, where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a composition, an apparatus, or a method described herein can be combined in a variety of ways without departing from the spirit and scope of the present teachings, whether explicit or implicit herein.

[32] The use of the terms "include," "includes", "including," "have," "has," or "having" should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

[33] The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term "about" is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term "about" refers to a ±10% variation from the nominal value unless otherwise indicated or inferred.

[34] It should be understood that the order of steps or order for performing certain actions is immaterial so long as the present teachings remain operable. Moreover, two or more steps or actions may be conducted simultaneously.

[35] As used herein, a "p-type semiconductor material" or a "donor" material refers to a semiconductor material, for example, an organic semiconductor material, having holes as the majority current or charge carriers. In some embodiments, when a p-type semiconductor material is deposited on a substrate, it can provide a hole mobility in excess of about 10^~5 cm /Vs. In the case of field-effect devices, a p-type semiconductor also can exhibit a current on off ratio of greater than about 10.

[36] As used herein, an "n-type semiconductor material" or an "acceptor" material refers to a semiconductor material, for example, an organic semiconductor material, having electrons as the majority current or charge carriers. In some embodiments, when an n-type semiconductor material is deposited on a substrate, it can provide an electron mobility in excess of about 10^"5 cm /Vs. In the case of field-effect devices, an n-type semiconductor also can exhibit a current on off ratio of greater than about 10.

[37] As used herein, "mobility" refers to a measure of the velocity with which charge carriers, for example, holes (or units of positive charge) in the case of a p-type semiconductor material and electrons (or units of negative charge) in the case of an n-type semiconductor material, move through the material under the influence of an electric field. This parameter, which depends on the device architecture, can be measured using a field-effect device or space-charge limited current measurements. [38] As used herein, a compound can be considered "ambient stable" or "stable at ambient conditions" when a transistor incorporating the compound as its semiconducting material exhibits a carrier mobility that is maintained at about its initial measurement when the compound is exposed to ambient conditions, for example, air, ambient temperature, and humidity, over a period of time. For example, a compound can be described as ambient stable if a transistor incorporating the compound shows a carrier mobility that does not vary more than 20% or more than 10% from its initial value after exposure to ambient conditions, including, air, humidity and temperature, over a 3 day, 5 day, or 10 day period.

[39] As used herein, fill factor (FF) is the ratio (given as a percentage) of the actual maximum obtainable power, (Pm or Vmp * Jmp), to the theoretical (not actually obtainable) power, (Jsc * Voc) . Accordingly, FF can be determined using the equation:

[40] FF = (Vmp * Jmp) / (Jsc * Voc)

[41] where Jmp and Vmp represent the current density and voltage at the maximum power point (Pm), respectively, this point being obtained by varying the resistance in the circuit until J * V is at its greatest value; and Jsc and Voc represent the short circuit current and the open circuit voltage, respectively. Fill factor is a key parameter in evaluating the performance of solar cells. Commercial solar cells typically have a fill factor of about 0.60% or greater.

[42] As used herein, the open-circuit voltage (Voc) is the difference in the electrical potentials between the anode and the cathode of a device when there is no external load connected.

[43] As used herein, the power conversion efficiency (PCE) of a solar cell is the percentage of power converted from absorbed light to electrical energy. The PCE of a solar cell can be calculated by dividing the maximum power point (Pm) by the input light irradiance (E, in W/m2) under standard test conditions (STC) and the surface area of the solar cell (Ac in m2) . STC typically refers to a temperature of 25 °C and an irradiance of 1000 W/m2 with an air mass 1.5 (AM 1.5) spectrum.

[44] As used herein, a component (such as a thin film layer) can be considered "photoactive" if it contains one or more compounds that can absorb photons to produce excitons for the generation of a photocurrent.

[45] As used herein, "solution-processable" refers to compounds (e.g., polymers), materials, or compositions that can be used in various solution-phase processes including spin-coating, printing (e.g., inkjet printing, gravure printing, offset printing and the like), spray coating, electrospray coating, drop casting, dip coating, and blade coating. [46] As used herein, a "semicrystalline polymer" refers to a polymer that has an inherent tendency to crystallize at least partially either when cooled from a melted state or deposited from solution, when subjected to kinetically favorable conditions such as slow cooling, or low solvent evaporation rate and so forth. The crystallization or lack thereof can be readily identified by using several analytical methods, for example, differential scanning calorimetry (DSC) and/or X-ray diffraction (XRD).

[47] As used herein, "annealing" refers to a post-deposition heat treatment to the semicrystalline polymer film in ambient or under reduced/increased pressure for a time duration of more than 100 seconds, and "annealing temperature" refers to the maximum temperature that the polymer film is exposed to for at least 60 seconds during this process of annealing. Without wishing to be bound by any particular theory, it is believed that annealing can result in an increase of crystallinity in the polymer film, where possible, thereby increasing field effect mobility. The increase in crystallinity can be monitored by several methods, for example, by comparing the differential scanning calorimetry (DSC) or X-ray diffraction (XRD) measurements of the as-deposited and the annealed films.

[48] As used herein, a "polymeric compound" (or "polymer") refers to a molecule including a plurality of one or more repeating units connected by covalent chemical bonds. A polymeric compound can be represented by the general formula:

[49] Throughout the specification, structures may or may not be presented with chemical names. Where any question arises as to nomenclature, the structure prevails.

[50] In a first embodiment of the present invention, a conjugated polymer that contains both Unit (I) and Unit (I

Unit (I) Unit (I I)

wherein:

X, in each occurrence, is independently selected from S or Se;

Mi and M2 are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 9:1 to 1:9.

[51] In one example, Mi and M2 are H atom, and X is S. [52] In another example, Ri and R2 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[53] In some examples, the number average molecular weight of the conjugated polymer is at least 20,000 gram/mole, and more preferably 40,000 gram/mole.

[54] In still another example, a composition is provided. The composition comprises the conjugated polymer dissolved or dispersed in a liquid medium, and the composition exhibits a red-shift of optical absorption peak of at least 50 nm, when the composition is cooled from 120°C to room temperature.

[55] In still another example, an organic photovoltaic device is disclosed. The organic photovoltaic device comprises a donor of the conjugated polymer, and one or more non-fullerene small molecular acceptors (SMA), wherein domains are formed in the donor:acceptor blend morphology. The domain size is preferred less than 20 nm. The small molecular acceptor (SMA) comprises perylene dimide (PDI) based structure.

[56] In still another example, an optical, electronic, or optoelectronic device is disclosed. The device comprises the conjugated polymer, and preferred, the device is selected from an organic field-effect transistor, an organic light-emitting transistor, or an organic photovoltaic device. polymer has a preferred formula of:

wherein:

R, in each occurrence, is independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[58] In a second embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer contains one or more repeating units of Formula

Unit (I) Unit (II) Formula (I) wherein: Ar is an aromatic unit that is not thiophene;

X, in each occurrence, is independently selected from S or Se;

Mi, M₂, M3 and M₄ are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 9:1 to 1:9.

[59] In one example, the conjugated polymer is selected from the group consisting

[60] In another example, the conjugated polymer is with Formula (IA) or Formula (IB) sho

Formula (IA)

R₂

Formula (IB)

wherein:

Arl and Ar2 are two aromatic units that are not thiophene, where Arl and Ar2 could be same or different; and

M₅, M₆, M₇, Mg, M₉, M₁₀, M11, M₁₂, M₁₃, M₁₄, M₁₅, M₁₆, M₁₇, M₁₈, M₁₉ and M₂₀ are independently selected from H or F. [61] In still another example, wherein Ar is selected from:

[62] In still another example, wherein Mi, M₂, M3 and M₄ are H atom, and X is S.

[63] In still another example, wherein Ri and R2 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[64] In still another example, wherein the number average molecular weight of the conjugated polymer is at least 20,000 gram/mole, and more preferably 40,000 gram/mole.

[65] In still another example, a composition is provided. The composition comprises the conjugated polymer dissolved or dispersed in a liquid medium, and the composition exhibits a red-shift of optical absorption peak of at least 50 nm, when the composition is cooled from 120°C to room temperature.

[66] In still another example, an organic photovoltaic device is disclosed. The organic photovoltaic device comprises a donor of the conjugated polymer, and one or more non-fullerene small molecular acceptors (SMA), wherein domains are formed in the donor:acceptor blend morphology. The domain size is preferred less than 20 nm. The small molecular acceptor (SMA) comprises perylene dimide (PDI) based structure. [67] In still another example, an optical, electronic, or optoelectronic device is disclosed. The device comprises the conjugated polymer, and preferred, the device is selected from an organic field-effect transistor, an organic light-emitting transistor, or an organic photovoltaic device.

[68] In a third embodiment of the present invention, a conjugated polymer is disclosed. The conjugated polymer is with Formula (II) containing at least one Unit (I) and at least one Unit (II) :

Formula (I I)

wherein:

Ar is an aromatic unit that is not thiophene;

X, in each occurrence, is independently selected from S or Se;

Mi, M₂, M₃, M4, M5 and M₆ are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 1:9 to 9:1.

Wherein

Mi ' is selected from H or F;

Ri ' is selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms; Ml and Μ could be same or different; and

RI and RI ' could be same or different. [70] In another example, the conjugated polymer is with Formula (IIA) shown below:

ormu a

Wherein

Ri' is selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms; and

Rl and Rl ' could be same or different.

[71] In still another example, Ar is selected from:

[72] In still another example, Mi, M₂, M₃, M₄, M₅, and M₆ are H atom, and X is S.

i₄ [73] In still another example, Rl and R2 are independently selected from

2-position branched alkyl groups with 4-40 C atoms.

[74] In this embodiment, an optical, electronic, or optoelectronic device comprising the conjugated polymer of above.

[75] In this embodiment, the device of above, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, and an organic photovoltaic device.

[76] In a fourth embodiment of the present invention, a conjugated polymer containi

Formula (I I I)

Wherein:

Arl and Ar2 are two aromatic units that are not thiophene, where Arl and Ar2 could be same or different;

X is S or Se atom;

Mi3, Mi4, Mis, Mi6, Mi7, Mis, Mi9 and M20 are independently selected from H or F; and

R₇ and Re are independently selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms.

[77] In this embodiment, the conjugated polymer of above, wherein:

R₇ and Rg could be independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[78] In this embodiment, the conjugated polymer of above, wherein:

Mi3, Mi4, Mis, Mi6, Mi?, Mis, M19 and M₂o are H atom.

[79] In this embodiment, the conjugated polymer of above, wherein Arl and Ar2 could be selected from:

[80] In this embodiment, an optical, electronic, or optoelectronic device comprising the conjugated polymer of above.

[81] In this embodiment, the device of above, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, and an organic photovoltaic device.

[82] In a fifth embodiment of the present invention, a conjugated polymer contains one or more re eating units with Formula (IV) below:

Formula (IV)

Wherein:

Arl and Ar2 are two aromatic units that are not thiophene, where Arl and Ar2 could be same or different;

X is S or Se atom;

M₂i, M22, M23, M24, M25, M26, M27 and M28 are independently selected from H or F; and R9 and Rio are independently selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms. [83] In this embodiment, the conjugated polymer of above, wherein:

Rg and Rio could be independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[84] In this embodiment, the conjugated polymer of above, wherein:

M₂i, M₂₂, M₂3, M₂4, M₂5, M₂₆, M₂₇ and M₂₈ could be H atom.

[85] In this embodiment, the conjugated polymer of above, wherein Arl and Ar2 could be selected from:

[86] In this embodiment, an optical, electronic, or optoelectronic device comprising the conjugated polymer of above.

[87] In this embodiment, the device of above, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, and an organic photovoltaic device.

[88] In a sixth embodiment of the present invention, three conjugated polymers containing one or more repeating units with Formula (V), Formula (VI), and Formula (VII) are provided:

Formula (VI)

Formula (VI I)

Wherein:

Arl and Ar2 are two different aromatic units that are not thiophene;

Ri i, Ri2, Ri3, Ri4, Ri5, Ri6, Ri7, Ri8 and R19 are independently selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms.

[89] In this embodiment, the conjugated polymer of above, wherein:

R11, R12, Ri3, Ri4, Ri5, Ri6, Ri7, Ri8 and R19 could be independently selected from

2-position branched alkyl groups with 4-40 C atoms.

[90] In this embodiment, the conjugated polymer of above, wherein Arl and Ar2 could be selected from:

[91] In this embodiment, an optical, electronic, or optoelectronic device comprising the conjugated polymer of above.

[92] In this embodiment, the device of above, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, and an organic photovoltaic device.

[93] In a seventh embodiment of the present invention, two monomers Formula (VIII) and Formula (IX) for forming the above-mentioned conjugated polymers are

Formula (VI I I) _{Formu|a (|χ)}

Wherein:

Ar is an aromatic unit that is not thiophene;

Y is Br or I;

R21, R22, R23 and R24 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

Ar is selected from:

[94] In an eighth embodiment of the present invention, three monomers Formula (X), Formula (XI), and Formula (XII) for forming the above-mentioned conjugated polymers are provided:

Wherein:

Ar is an aromatic unit that is not thiophene;

Y is Br or I;

R24, R25, R26 R27, R28 and R24 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

Ar is selected from:

Wherein: R33, R34, R35, R36, R37, R38, R39> R40, R41, R42, R43, R44, R45, R46, R47 and R48 are independently selected from 2-position branched alkyl groups with 4-40 C atoms. R49 is selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms.

[96] In one example, the first conjugated polymer of above, wherein R33 is 2-position branched C8C12, R34 is 2-position branched C6C9.

[97] In this embodiment, an optical, electronic, or optoelectronic device comprising the conjugated polymer of above.

[98] In this embodiment, the device of above, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, and an organic photovoltaic device.

In a tenth embodiment of the present invention, several conjugated

wherein:

R, in each occurrence, is independently selected from 2-position branched alkyl groups with 4-40 C atoms.

[100] It was surprising found polymers containing above building blocks exhibit a dramatic LUMO and HOMO levels decrease due to the strong electronic withdrawing ability of the ester group on the thiophene. As the result, the blends (polymer/fullerene or polymer/small molecule) usually show high Voc, such as, the P3TEA:SF-PDI₂ exhibits a high Voc of 1.11 V. The bandgap of P3TEA polymer is 1.66 eV, which is calculated from the absorption onset. Together with high Voc, the blend exhibits a low voltage loss of 0.55 eV. Thus it is highly possible that the blend using the thiophene carboxylate-based polymers as the donor will show high Voc because of the deeper HOMO levels of the polymers.

[101] Surprisingly and beneficially, polymer exhibiting such building block tend to form an optimal morphology with small molecule acceptor, as evidenced by the AFM and TEM images. As a result, high Voc and Jsc can be achieved simultaneously, which is due to a high PCE efficiency of 9.5%. Our OSC system has fundamental implications on developing more efficient solar cells because it effectively unlocks the trade-off between the Voc and Jsc.

EXAMPLES

Example 1 - Synthesis of Monomers Dibromof BT-Ε,Α and polymer

P3TEA

Scheme S1 : Synthetic route for DibromoffBT-E

DibromoffBT-E

[103] 2-octyldodecyl thiophene-3-carboxylate (SI). A solution of thiophene-3-carboxylic acid (1, 5.126 g, 40 mmol) in 150 mL DCM was stirred at room temperature under N₂. Then 4-Dimethylaminopyridine (1.466 g, 12 mmol), a DCM solution of Ν,Ν'-dicyclohexylcarbodiimide ( 9904 mg , 48 mmol ) and 2-octyldodecan-l-ol (2, 23.88 g, 80 mmol ) were added to the system. The reaction mixture was stirred for another 12 hours. 50 mL distilled water was added and the reaction mixture was filtered, diluted with hexane and washed with water and brine. The organic layer was dried over Na₂S0₄, filtered and concentrated. Then the residue was purified with silica gel chromatography to provide pure product as transparent liquid (17.25 g, 92% yield). 1H NMR (400 MHz, CDC1₃) δ 8.08 (d, / = 1.7 Hz, 1H), 7.54 - 7.51 (m, 1H), 7.31 - 7.28 (m, 1H), 4.18 (d, / = 5.6 Hz, 2H), 1.74 (d, / = 4.4 Hz, 1H), 1.41 - 1.22 (m, 32H), 0.88 (t, / = 6.3 Hz, 6H). ¹³C NMR (101 MHz, CDC1₃) δ 163.13, 134.27, 132.57, 128.09, 126.07, 67.68, 37.63, 32.12, 32.11, 31.64, 30.15, 29.85, 29.80, 29.76, 29.55, 29.51, 26.96, 22.89, 22.88, 14.31. HRMS (MALDI+) Calcd for C₂₅H₄₄0₂S (M⁺): 408.3062, Found: 408.3080. [104] 2-octyldodecyl 2-(trimethylsilyl)thiophene-3-carboxylate (S2). A solution of 3-(2-octyldodecyl)thiophene (SI, 2.468 g, 7 rnmol) in 40 mL THF was cooled to -78 °C under N₂. A solution of lithium diisopropylamide (2 M, 4.2 mL, 8.4 mmol) was added drop wise and the mixture was stirred at -78 °C for lh. Then liquid Chlorotrimethylsilane (1.1 mL, 8.4 mmol) was added drop wise and the reaction mixture was return to room temperature and stirred overnight. 30 mL distilled water was added and the reaction mixture was filtered, diluted with hexane and washed with water and brine. The organic layer was dried over Na2S0₄, filtered and concentrated. Then the residue was purified with silica gel chromatography to provide pure product as transparent liquid ( 1.28 g, 43% yield). *H NMR (400 MHz, CDC1₃) δ 7.63 (d, J = 4.8 Hz, 1H), 7.47 (d, 7 = 4.8 Hz, 1H), 4.19 (d, J = 5.8 Hz, 2H), 1.77 (d, J = 5.3 Hz, 1H), 1.43 - 1.23 (m, 32H), 0.89 (t, J = 6.6 Hz, 6H), 0.41 (s, 9H). ¹³C NMR ( 101 MHz, CDC1₃) δ 164.05, 150.07, 139.27, 130.85, 129.65, 67.61, 37.68, 32.15, 32.13, 31.61, 30.20, 29.88, 29.82, 29.78, 29.58, 29.54, 26.94, 22.92, 22.90, 14.33, -0.23. HRMS (MALDI+) Calcd for C2₈H52O2SS1 (M ⁺): 480.3457, Found: 480.3477.

[105] 2-octyldodecyl 5-(tributylstannyl)-2- (trimethylsilyl)thiophene-3- carboxylate (S3). A solution of 2-octyldodecyl

2-(trimethylsilyl)thiophene-3-carboxylate 3-(2-octyldodecyl)thiophene (S2, 2.124 g, 5 mmol) in 30 mL THF was cooled to -78 °C under N₂. A solution of lithium diisopropylamide (2 M, 2.8 mL, 5.5 mmol) was added dropwise and the mixture was stirred at -78 °C for lh. Then tributyltin chloride ( 1.6 mL, 6 mmol) was added dropwise and the reaction mixture was return to room temperature and stirred overnight. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na2S0₄, filtered and the solvent was evaporated to get the crude product as yellow oil, which is directly used without further purification.

[106] bis(2-octyldodecyl)5,5'-(5,6-difluorobenzo[c][l,2,5]thiadiazole-4,7-diyl)bi s(2-bromothiophene-3-carboxylate) (DibromoffBT-E). A mixture of 2-octyldodecyl 5-(tributylstannyl)-2-(trimethylsilyl)thiophene-3-carboxylate (S3, 3.388 g, -4.4 mmol), 4, 7-dibromo-5,6-difluoro-2,l ,3-benzothiadiazole (3, 607 mg, 2 mmol), Pd₂(dba)₃(92 mg, 0.1 mmol) and P(o-tol)₃(122 mg, 0.4 mmol) in 20 mL Toluene was refluxed at 100 °C overnight under N₂. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na2S0₄, filtered and concentrated. Then the residue was simply purified with silica gel chromatography by a short column to give crude product as yellow oil, which is directly used without further purification.

[107] The crude product mixture was added to a mixture of N-Bromosuccinimide (784 mg, 4.4 mmol) and silica gel (10 mg) in 30 mL chloroform and 6 mL trifluoroacetic acid at 0 °C. The reaction mixture was warmed to r.t. and stirred overnight. After washed with water, the organic phase was dried with Na2S0₄ and the solvent was evaporated. Then the residue was purified with silica gel chromatography to provide pure product as orange solid (1.715 g, 75 % yield). *H NMR (400 MHz, CDC1₃) δ 8.44 (s, 2H), 4.26 (d, J = 5.6 Hz, 4H), 1.80 (dd, J = 11.1, 5.5 Hz, 2H), 1.52 - 1.21 (m, 64H), 0.90 - 0.83 (m, 12H). ¹³C NMR (101 MHz, CDC1₃) δ 162.00, 151.51, 151.30, 148.90, 148.70, 148.27, 148.23, 148.20, 132.96, 132.90, 132.86, 132.03, 131.80, 123.74, 123.71, 111.07, 111.03, 110.98, 110.94, 68.31, 37.62, 32.14, 32.13, 31.67, 30.23, 29.90, 29.88, 29.85, 29.80, 29.58, 29.56, 27.01, 22.89, 14.31. ¹⁹F NMR (376 MHz, CDC1₃) δ -126.87. HRMS (MALDI+) Calcd for C56H84Br₂F2N204S3 (M ⁺): 1142.3908, Found: 1142.4729.

[108] bis(2-octyldodecyl)5,5"-(5,6-difluorobenzo[c][l,2,5]thiadiazole-4,7-diyl)b is(4'-(2-hexylnonyl)-[2,2'-bithiophene]-3-carboxylate) (S4). A mixture of DibromoffBT-E (1.144 g, 1 mmol), tributyl(4-(2-hexylnonyl)thiophen-2-yl)stannane (4, 1.343 g, 2.3 mmol), Pd₂(dba)₃ (46 mg, 0.05 mmol) and P(o-tol)₃ (61 mg, 0.2 mmol) in 20 mL THF was refluxed at 80 °C overnight under N₂. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na2S0₄, filtered and concentrated. Then the residue was purified with silica gel chromatography to give product as red oil (1.429 g, 91% yield). *H NMR (400 MHz, CDCI₃) δ 8.64 (s, 2H), 7.42 (d, J = 1.1 Hz,2H), 7.03 (s, 2H), 4.22 (d, J = 5.8 Hz, 4H), 2.58 (d, J = 6.7 Hz, 4H), 1.76 (s, 2H), 1.66 (s, 2H), 1.28 (dd, J = 24.6, 14.4 Hz, 108H), 0.93 - 0.82 (m, 24H). ¹³C NMR (101 MHz, CDC1₃) δ 163.41, 151.63, 151.43, 149.03, 148.80, 148.76, 148.72, 146.35, 142.59, 142.12, 134.38, 132.85, 131.86, 129.19, 129.01, 127.90, 124.96, 124.54, 120.83, 111.34, 111.25, 111.21, 68.07, 39.12, 37.61, 35.16, 33.55, 32.15, 31.65, 30.26, 30.24, 29.95, 29.93, 29.89, 29.87, 29.83, 29.60, 29.58, 27.01, 26.87, 26.83, 22.92, 22.90, 14.33, 14.31. ¹⁹F NMR (376 MHz, CDC1₃) δ -127.21. HRMS (MALDI+) Calcd for G^H^^C Ss (M⁺): 1570.0201, Found: 1570.0461.

[109] bis(2-octyldodecyl)5,5"-(5,6-difluorobenzo[c][l,2,5]thiadiazole-4,7-diyl)b is(5'-bromo-4'-(2-hexylnonyl)-[2,2'-bithiophene]-3-carboxylate)

(DibromoffBT-Ε,Α). N-Bromosuccinimide (320 mg, 1.8 mmol) was added to a mixture of S4 (1.414 g, 0.9 mmol) and silica gel (10 mg) in 10 mL chloroform at 0 °C. The reaction mixture was stirred for 15 minutes. After washed with water, the organic phase was dried with Na2S0₄ and the solvent was evaporated. The residue was purified with flash column chromatography (eluent: n-hexane) to get the product as orange solid (1.540 g, 99% yield). *H NMR (400 MHz, CDC1₃) δ 8.61 (s, 2H), 7.28 (s, 2H), 4.23 (d, J = 5.8 Hz, 4H), 2.53 (d, J = 7.1 Hz, 4H), 1.78 (d, J = 4.4 Hz, 2H), 1.71 (s, 2H), 1.30 (t, J = 23.5 Hz, 108H), 0.92 - 0.81 (m, 24H). ¹³C NMR (101 MHz, CDC1₃) δ 163.27, 151.66, 151.46, 149.06, 148.86, 148.71, 148.67, 145.45, 141.74, 134.35, 132.77, 131.18, 129.23, 127.85, 114.26, 111.27, 111.19, 111.15, 68.25, 38.79, 37.62, 34.38, 33.58, 32.15, 31.67, 30.28, 30.23, 29.93, 29.89, 29.88, 29.83, 29.59, 27.02, 26.78, 26.74, 22.92, 22.90, 14.34, 14.32. ¹⁹F NMR (376 MHz, CDC1₃) δ -126.97. HRMS (MALDI+) Calcd for C₉₄Hi₄₈Br₂F₂N₂0₄S₅ (M ⁺): 1726.8357, Found: 1726.8539.

[110] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-E (25.9 mg, 0.015 mmol),

5,6-difluoro-4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (6, 10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N₂.The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (13.4 mg, 37 %). *Η NMR (400 MHz, CDC1₃) δ 8.71 (s, 1H), 8.37 (d, J = 3.6 Hz, 1H), 7.56 (s, 1H), 7.43 (d, J = 3.8 Hz, 1H), 4.34 (d, J = 5.8 Hz, 2H), 2.93 (d, J = 6.2 Hz, 2H), 1.89 (s, 2H), 1.55 - 1.25 (m, 54H), 1.00 - 0.86 (m, 12H). GPC: Mn: 48.4 kDa; Mw: 100.2 kDa; PDI=2.07. Anal.Calcd for Cio8Hi5₂F₄N₄0₄S₈: C, 68.17; H, 8.05; N, 2.94. Found C, 68.20; H, 7.90; N, 2.84.

[Ill] Example 2 - Synthesis of polymer P3TEA with different alkyl chains

[112] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-E (29.3 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2.The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (20.1 mg, 61 %).

[113] Example 3 - Synthesis of Monomer DibromoffBT-A,E and according polymer PffBT3T-A.E

[114] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-A,E (24.7 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2-The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (15.3 mg, 52 %).

[115] Example 4 - Synthesis of Monomer DibromoffBT-EAA and according polymer PffBT4T-EAA

[116] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-EAA (35.5 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2-The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (17.8 mg, 47 %).

[117] Example 5 - Synthesis of Monomer DibromoffBT-AEA and according polymer PffBT4T-AEA

[118] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-AEA (35.5 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2-The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (14.6 mg, 38 %).

[119] Example 6 - Synthesis of Monomer DibromoffBT-AAE and according polymer PffBT4T-AAE

[120] Microwave assisted polymerization. To a mixture of monomer DibromoffBT-AAE (35.5 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2-The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (16.5 mg, 43 %).

[121] Example 7 - Synthesis of Monomer Dibromof BTSe-E,A and according polymer PffBT4TSe-E,A

[122] Microwave assisted polymerization. To a mixture of monomer DibromoffBTSe-E,A (26.3 mg, 0.015 mmol),

5,6-difluoro-4 -bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][l,2,5]thiadiazole (10.0 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N2.The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with chloroform. This solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (13,9 mg, 49 %).

[123] Example 8 - synthesis of related polymer S9 and S17

[124] Synthesis

[125] To a solution of SI (406 mg, 0.352 mmol), Pd₂(dba)₃(10 mg, 0.02 mmol) and P(o-tol)₃(22 mg, 0.07 mmol) in 20 mL Toluene was added S2 (625 mg, 0.88 mmol) under N₂, the reaction was refluxed overnight. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na₂S0₄, filtered and concentrated. Then the residue was simply purified with silica gel chromatography by column to give red product, which is directly used without further purification.

[126] To a solution of S33 (485 mg, 0.267mmol) in 20 mL CHC1₃ was added N-Bromosuccinimide (178 mg, 0.90 mmol) at 0D, the reaction was stirred overnight. After washed with water, the organic phase was dried with Na₂S0₄ and the solvent was evaporated. Then the residue was purified with silica gel chromatography to provide pure product S4 as dark red solid.

[127] To a solution of S4 (724 mg, 0.62 mmol), Pd₂(dba)₃ (18 mg, 0.031 mmol) and P(o-tol)₃(37 mg, 0.124 mmol) in 20 mL Toluene was added S5 (578 mg, 1.55 mmol) under N₂, the reaction was refluxed overnight. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na₂S0₄, filtered and concentrated. Then the residue was simply purified with silica gel chromatography by column to give S6 as dark red oil, which is directly used without further purification.

[128] To a solution of S6 (343 mg, 0.172mmol) in 20 mL CHC1₃ was added N-Bromosuccinimide (58 mg, 0.33 mmol) at 0D, the reaction was stirred overnight. After washed with water, the organic phase was dried with Na₂S0₄ and the solvent was evaporated. Then the residue was purified with silica gel chromatography to provide pure product S7 as dark red oil.

[129] Microwave assisted polymerization. To a mixture of monomer S7 (79.1 mg, 0.037 mmol) >

4,7-bis(5"-bromo-3,4'-bis(2-decyltetradecyl) 2,2':5 2"-terthiophen]-5-yl)-5,6-difluoro benzo[c][l,2,5]oxadiazole (24.3 mg, 0.037 mmol), Pd₂(dba)₃ (0.6 mg, 0.007 mmol) and P(o-tol)₃(1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N₂. The reaction mixture was sealed and heated to 140□ for 2 hours using a microwave reactor. The mixture was cool to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The precipitate was collected and further purified by Soxhlet extraction with acetone, chloroform and toluene. The polymer was recovered as a solid from the toluene fraction to the afforded the product as a dark blue solid.

[130] Synthesis of S 17

[131] To a solution of Sll (396 mg, 0.347 mmol), Pd₂(dba)₃(20 mg, 0.047 mmol) and P(o-tol)₃(42 mg, 0.14 mmol) in 20 mL Toluene was added S12 (1250 mg, 2.2 mmol) under N₂, the reaction was refluxed overnight. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na₂S0₄, filtered and concentrated. Then the residue was simply purified with silica gel chromatography by column to give red product S13, which is directly used without further purification.

[132] To a solution of S13 (373 mg, 0.218mmol) in 20 mL CHC1₃ was added N-Bromosuccinimide (166 mg, 0.93 mmol) at 0D, the reaction was stirred overnight. After washed with water, the organic phase was dried with Na₂S0₄ and the solvent was evaporated. Then the residue was purified with silica gel chromatography to provide pure product as red solid S14.

[133] To a solution of S14 (364 mg, 0.195 mmol), Pd₂(dba)₃(5.6 mg, 0.01 mmol) and P(o-tol)₃(12.0 mg, 0.04 mmol) in 20 mL Toluene was added S5 (217 mg, 0.584 mmol) under N₂, the reaction was refluxed overnight. A solution of KF in water was added and the reaction mixture was filtered, diluted with hexane and washed with KF solution, water and brine. The organic layer was dried over Na₂S0₄, filtered and concentrated. Then the residue was simply purified with silica gel chromatography by column to give dark red product S15, which is directly used without further purification. [134] To a solution of S15 (214 mg, 0.114mmol) in 15 mL CHC1₃ was added N-Bromosuccinimide (38.1 mg, 0.38 mmol) at 0D , the reaction was stirred overnight. After washed with water, the organic phase was dried with Na₂S0₄ and the solvent was evaporated. Then the residue was purified with silica gel chromatography to provide pure product as dark red solid SI 6.

[135] Microwave assisted polymerization. To a mixture of monomer S16 (53 mg, 0.026 mmol) >

4,7-bis(5"-bromo-3,4'-bis(2-decyltetradecyl) 2,2':5 2"-terthiophen]-5-yl)-5,6-difluoro benzo[c][l,2,5]oxadiazole (17.5 mg, 0.026 mmol), Pd₂(dba)₃ (0.6 mg, 0.007 mmol) and P(o-tol)3(1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N₂. The reaction mixture was sealed and heated to 140 ^°C for 2 hours using a microwave reactor. The mixture was cool to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The precipitate was collected and further purified by Soxhlet extraction with acetone, chloroform and toluene. The polymer was recovered as a solid from the toluene fraction to the afforded the product as a dark blue solid.

[136] Example 9 - synthesis of comparative polymer PffBT4T-E

[137] Microwave assisted polymerization.To a mixture of monomer DibromoffBT-E (17.2 mg, 0.015 mmol),5,5'-bis(trimethylstannyl)-2,2'-bithiophene (5,7.4 mg, 0.015 mmol), Pd₂(dba)₃ (0.6 mg,0.0007 mmol) and P(o-tol)₃ (1.2 mg, 0.004 mmol) in a microwave vial equipped with a stirring bar, 0.20 mL of chlorobenzene was added in a glove box protected with N₂.The reaction mixture was then sealed and heated to 140 °C for 2 hours using a microwave reactor. The mixture was cooled to r.t. and 10 mL of chlorobenzene was added before precipitated with methanol. The solid was collected by filtration, subsequently subjected to Soxhlet extraction with different volume ratio of chloroform and acetone. The polymer was finally collected from 100% chloroform. This ratio solution was then concentrated by evaporation, precipitated into methanol. The solid was collected by filtration and dried in vacuum to get the polymer as dark purple solid (8.7 mg, 35 %). 1H NMR (400 MHz, CDC1₃) δ 8.70 (s, 1H), 7.65 (s, 1H), 7.30 (s, 1H), 4.33 (d, / = 5.8 Hz, 2H), 1.87 (s, 1H), 1.53 - 1.24 (m, 32H), 0.96 - 0.88 (m, 6H). GPC: Mn: 89.4 kDa; Mw: 181.7 kDa; PDI=2.03. Anal.Calcd for C₆4H₈₈F₂N₂0₄S5 : C, 66.98; H, 7.73; N, 2.44. Found C, 67.02; H, 7.56; N, 2.45.

Example 10 - Device Fabrication

[138] Photovoltaic cell fabrication and measurements

[139] Pre-patterned ITO-coated glass with a sheet resistance of -15 Ω per square was used as the substrate. It was cleaned by sequential sonications in soap deionized water, deionized water, acetone, and isopropanol for 30 min at each step. After UV/ozone treatment for 60 min, a ZnO electron transport layer was prepared by spin-coating at 5000 rpm from a ZnO precursor solution (diethyl zinc). Active layer solutions (D/A ratio 1 :1.5, polymer concentration 9 mg/ml) were prepared in 1,2,4-trimethylbenzene (TMB) with 2.5% of 1,8-octanedithiol (ODT). To completely dissolve the polymer, the active layer solution should be stirred on hotplate at 100 °C for at least 1 hour. Before spin coating, both the polymer solution and ITO substrate are preheated on a hotplate at about 90 °C. Active layers were spin-coated from the warm polymer solution on the preheated substrate in a N₂ glovebox at 1500 rpm to obtain thicknesses of -120 nm. The polymer:SMA blend films were then thermally annealed before being transferred to the vacuum chamber of a thermal evaporator inside the same glovebox. At a vacuum level of 3xl0^"6 Torr, a thin layer (20 nm) of 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 in forward direction under AM1.5G (100 mW cm^"2) at room temperature using a Newport solar simulator. The dwell times is 2 s and the speed is 0.8 V/s. We also have conducted both forward and backward scans, which yielded identical result. The light intensity was calibrated using a standard Si diode (with KG5 filter, purchased from PV Measurement) to bring spectral mismatch to unity. J-V characteristics were recorded using a Keithley 236 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 and certified cells have the area of 4.18 mm². EQE was characterized using a Newport EQE system equipped with a standard Si diode. Monochromatic light was generated from a Newport 300W lamp source. EQE data from 300 nm to 850 nm is provided and calculated /_sc (12.79 mA cm^"2) is comparable to that derived from J-V plots. In our experiments, over 30 devices have been tested, and the average efficiency is with 0.4% of our best value. We have also performed stability analysis, which indicates our organic solar cells are reasonably stable (~ 0.2-0.3% decrease in efficiency after two weeks).

[140] Example 11 - Related Device parameters [141] Table 1. Photovoltaic device parameters of PSCs based on the four polymer: SF-PDI₂ blends.

Voc Jsc FF Efficiency

P3TEA:SP-PDI₂ 1.11 13.27 0.64 9.50

P3TEA(changed alkyl

chain):SP-PDI₂ 1.10 12.79 0.59 8.32

PffBT3T-A,E-SF-PDI₂ 1.18 11.09 0.56 7.28

PffBT4T-E:SF-PDI₂ 1.07 9.44 0.52 5.26

[142] Example 12 - Comparison of crystallinitv among several polymers

FIG.5 is the GIWAXS profiles of the pure PffBT4T-20D (in the figure, short-named as Y5), pure PffBT4T-E(in the figure, short-named as G5), PffBT4T-20D:SF-PDI₂(Y5/Jsl), PffBT4T-E:SF-PDI₂(G5/Jsl), pure PffBT3T-l,2(in the figure, short-named as S26), pure P3TEA(in the figure, short-named as G17), PffBT3T-l,2:SP-PDI₂(S26/Jsl), P3TEA:SP-PDI₂(G17/Jsl) films, in which Jsl is the short name of PDI-based non-fullerene acceptor, SF-PDI2. We can see that the (010) peak of PffBT4T-E is sharper (higher FWHM value) than PffBT4T-20D, and the q location of the peak is larger, in both pure and blend film. As a result, PffBT4T-E shows enhanced pi-pi stacking and crystallinity than PffBT4T-20D, which has no alkyl ester group along the polymer chain. For the ter-thiophene polymer P3TEA, half of the alkyl groups are replaced with alkyl ester groups. In pure/blend film, P3TEA shows sharper (010) peaks and larger q location compared with PffBT3T-l,2, exhibiting its stronger crystallinity. These indicate that polymers with alkyl ester side chains have higher crystallinity.

[143] Example 13 - Comparison of morphology among several polymer-based blends

[144] FIG.6 shows R-SoXS profiles of the PffBT4T-20D:SF-PDI₂(Y5/Jsl), PffBT4T-E:SF-PDI₂ G5/Jsl), PffBT3T-l ,2:SP-PDI₂(S26/Jsl) and

P3TEA:SP-PDI₂(G17/Jsl) four blend films. For PffBT4T-20D:SF-PDI₂ blend film, its average domain size is 15.15 nm and the relative domain purity is 0.3368. When it turns to PffBT4T-E:SF-PDI₂, domain size of the blend film is increased to 44.48nm and the relative domain purity to 0.5699. So is the situation in the quarter-thiophene system PffBT3T-l,2 vs P3TEA. These two systems give us the conclusion that the esterified polymer can form larger and purer domains with the small molecular acceptor. However, for the best-performing G17/Jsl blend with 50% alkyl and 50% alkyl ester chains, the domain size is the smallest, <10 nm, which is an unprecedented value for OSCs.

Claims

CLAIMS What is claimed is:

1. A conjugated polymer containing both Unit (I) and Unit (II) shown below:

Unit (I) Unit (I I) wherein:

X, in each occurrence, is independently selected from S or Se;

Mi and M2 are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 9:1 to 1:9.

2. The conjugated polymer of claim 1, wherein:

Mi and M2 are H atom; and

X is S.

3. The conjugated polymer of claim 2, wherein:

Ri and R2 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

4. The conjugated polymer of claim 3 , wherein the number average molecular weight of the conjugated polymer is at least 20,000 gram/mole.

5. A composition comprising the conjugated polymer of claim 3 dissolved or dispersed in a liquid medium, and the composition exhibits a red-shift of optical absorption peak of at least 50 nm, when the composition is cooled from 120°C to room temperature.

6. An organic photovoltaic device comprising a donor of the conjugated polymer of claim 1, and one or more non-fullerene small molecular acceptors (SMA), wherein domains are formed in the donor:acceptor blend morphology.

7. The organic photovoltaic device of claim 6, wherein the small molecular acceptor (SMA) comprises perylene dimide (PDI) based structure.

8. The organic photovoltaic device of claim 6, wherein the domain size is less than 20 nm.

9. An optical, electronic, or optoelectronic device comprising the conjugated polymer of claim 1.

10. The device of claim 9, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, or an organic photovoltaic device.

11. The conjugated polymer of claim 1, wherein the conjugated polymer is selected

wherein:

R, in each occurrence, is independently selected from 2-position branched alkyl groups with 4-40 C atoms.

12. The conjugated polymer of claim 1, wherein the conjugated polymer has a formula of:

₄o

wherein:

R, in each occurrence, is independently selected from 2-position branched alkyl groups with 4-40 C atoms.

13. A conjugated polymer containing one or more repeating units of Formula (I),

Unit (I) Unit (II) Formula (I) wherein:

Ar is an aromatic unit that is not thiophene;

X, in each occurrence, is independently selected from S or Se;

Mi, M₂, M3 and M₄ are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 9:1 to 1:9.

14. The conjugated polymer of claim 13, wherein the conjugated polymer is selected

15. The conjugated polymer of claim 12, wherein the conjugated polymer is with Formula (IA) or Formula (IB) shown below:

Formula (IB) wherein:

Arl and Ar2 are two aromatic units that are not thiophene, where Arl and Ar2 could be same or different; and

M₅, M₆, M₇, M₈, M₉, M₁₀, M_n, M₁₂, M₁₃, M₁₄, M₁₅, M₁₆, M₁₇, M₁₈, M₁₉ and M₂₀ are independently selected from H or F.

16. The conjugated polymer of claim 13, wherein Ar is selected from:

17. The conjugated polymer of claim 13, wherein:

Mi, M₂, M₃ and M₄ are H atom; and

X is S.

18. The conjugated polymer of claim 13, wherein:

Ri and R2 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.

19. The conjugated polymer of claim 18, wherein the number average molecular weight of the conjugated polymer is at least 20,000 gram/mole.

20. A composition comprising the conjugated polymer of claim 18 dissolved or dispersed in a liquid medium, and the composition exhibits a red-shift of optical absorption peak of at least 50 nm, when the composition is cooled from 120°C to room temperature.

21. An organic photovoltaic device comprising a donor of the conjugated polymer of claim 18, and one or more non-fullerene small molecular acceptors (SMA), wherein domains are formed in the donor:acceptor blend morphology.

22. The organic photovoltaic device of claim 21, wherein the small molecular acceptor (SMA) comprises perylene dimide (PDI) based structure.

23. The organic photovoltaic device of claim 21, wherein the domain size is less than 20 nm.

24. An optical, electronic, or optoelectronic device comprising the conjugated polymer of claim 13.

25. The device of claim 24, wherein the device is selected from an organic field-effect transistor, an organic light-emitting transistor, or an organic photovoltaic device.

26. A conjugated polymer with Formula (II) containing at least one Unit (I) and at least one Unit (II) :

Unit (!) Unit: (!i) Unit (iii).

Formula (I I) wherein:

Ar is an aromatic unit that is not thiophene;

X, in each occurrence, is independently selected from S or Se;

Mi, M₂, M₃, M4, M5 and M₆ are independently selected from H or F; and

Ri and R2 are independently selected from straight-chain, branched or cyclic alkyl groups with 1-40 C atoms;

wherein the number ratio of Unit (I) and Unit (II) in the polymer chain ranges from 1:9 to 9:1.

27. The conjugated polymer of claim 26, wherein the conjugated polymer is selected

Wherein

Mi' is selected from H or F;

Ri' is selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms; Ml and Μ could be same or different; and

RI and RI ' could be same or different.

28. The conjugated polymer of claim 26 wherein the conjugated polymer is with Formula (IIA) shown below:

ormu a

Wherein

Ri' is selected from straight-chain, branched or cyclic alkyl groups with 2-40 C atoms; and

RI and RI ' could be same or different.

29. The conjugated polymer of claim 26, wherein Ar is selected from:

30. The conjugated polymer of claim 25, wherein:

Mi, M₂, M₃, M4, M₅, and M₆ are H atom; and

X is S.

31. The conjugated polymer of claim 25, wherein:

Ri and R2 are independently selected from 2-position branched alkyl groups with 4-40 C atoms.