WO2012087243A1

WO2012087243A1 - New p-type low bandgap polymers and their use

Info

Publication number: WO2012087243A1
Application number: PCT/SG2011/000444
Authority: WO
Inventors: Zhun Ma; Zhikuan Chen; Siew Lay Lim; Jun Li
Original assignee: Agency For Science, Technology And Research
Priority date: 2010-12-20
Filing date: 2011-12-20
Publication date: 2012-06-28

Abstract

Synthesis of a benzothiadiazole/thiophene-based oligomer/polymer for bulk heteroj unction photovoltaic cells. The polymer/oligomer comprises electron donating units such as fluorene, dibenxothiophene, dibenzosilole dihydroindenofluorene etc and electron withdrawing units such as benzothiadiazole and is represented by formula (I).

Description

NEW P-TYPE LOW BANDGAP POLYMERS AND THEIR USE

FIELD OF THE INVENTION

[001 ] The present technology relates to the development of low bandgap copolymers and devices using the same.

BACKGROUND OF THE INVENTION

[002] Organic photovoltaics have attracted much attention in the past two decades. Great progress has been made recently due to many new materials and new processes developed. The most investigated and performing polymeric solar cells are made with regioregular poly(3-hexylthiophene) (P3HT) as donor material and achieve an efficiency surpassing 5%. However, the main disadvantage of this polymer is the poor matching of its photon absorbance with the solar cell spectrum. The bandgap of P3HT is around 1.9 eV, limiting the absorbance to below a wavelength of 650 nm. It has been calculated that at 650 nm only 22.4% of the total amount of photons can be harvested. Since low bandgap polymers can increase the total amount of photons harvested from the solar spectrum, they can have great potential use in polymeric solar cells. However, narrowing of the polymeric bandgap will decrease the open circuit voltage thus may eventually result in a decrease in power conversion efficiency. When the low bandgap polymers are paired with the most commonly used acceptor [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM), the calculated optimal bandgap of the donor polymer will be from 1.3 to 1.9 eV.

[003] The power conversion efficiency (PCE) of OPVs is determined by short circuit current (Jsc), open circuit voltage (Voc), and fill factor (FF).

[004] Very generally, the Voc is governed by the energy levels of donor and acceptor. The Jsc depends on the photon absorption of the active layer and charge carriers generated at the donor-acceptor interface. Thus, using low bandgap polymer with higher Voc is beneficial to increase total PCE performance.

[005] The third parameter, which will affect PCE of OPVs, is fill factor (FF). The fill factor of a device depends on the charge dissociation, the charge carrier transport, and the recombination processes. A good hole transport capability is of vital importance for proper device operation. When hole and electron transport are unbalanced, a build up of space charge results in a square root dependence of the photocurrent on voltage, resulting in low fill factors. Charge transporting property is mainly determined by the intrinsic charge mobility of the donor/acceptor and also the morphology. Formation of an interpenetrating network with an acceptor requires the polymer to have a certain interaction with the acceptor, preventing severe phase separation. Also, the polymer should exhibit some degree of structural ordering which is induced by the rod-like behavior of these polymers.

[006] This structural ordering enhances the transport properties such as the hole mobility, thereby reducing the limitation of a space charge limited photocurrent. Therefore, using low bandgap polymers as the donor for high PCE OPV devices, high charge mobility, e.g. hole mobility and good control of the film morphology are critical.

[007] Generally, low bandgap polymers are developed through combining an electron donating unit and an electron withdrawing unit into the backbone to form a D-A structure to reduce the bandgap. Many aromatic rings with electron-rich structures are employed as electron donor for copolymerization, such as fluorene, dibenzothiophene, dibenzothiophene sulfone, benzodithiophene, dithienothiophene, cyclopentadithiophene, dithioneosilole, dibenzosilole, dibenzothienopyrrole, dihydroindenofluorene and naphthalene. Meanwhile, the incorporation of these building blocks may increase the Voc of the polymers. On the other hand, benzothiadiazole is a widely used electron withdrawing block in low bandgap polymers. [008] Copolymers containing both the above-mentioned aromatic units as the electron donating block and benzothiadiazole as the electron withdrawing unit have been developed and PCE surpassing 5% in OPV devices have been achieved. Examples include but are not limited to silole-containing polythiophenes, silafluorene containing polymers, carbazole containing polymers or indolocarbazole containing polymers. However, low bandgap copolymers composed of both oligothiophene unit and the above two units have not yet demonstrated good PCE.

[009] Additionally, despite the number of low bandgap polymers reported for OPV, only a few of low bandgap polymers have sufficiently high Voc and subsequent high PCE for organic solar cell application. Furthermore, for many real applications such as power generating windows and sunshades, issues such as transparency of OPV devices have not been adequately addressed. SUMMARY OF THE INVENTION

[0010] The present invention relates to the development of low bandgap copolymers.

[001 1] In one aspect of the present invention benzothiadiazole- and oligothiophene-containing semiconductor materials for electronic devices such as organic photovoltaics, organic thin film transistors (OTFTs), photodetectors and chemical sensors are proposed.

[0012] In another aspect of the invention an OPV device comprising such benzothiadiazole- and oligothiophene-containing semiconductor materials.

[0013] In a further aspect of the invention a thin-film OPV device comprising such benzothiadiazole- and oligothiophene-containing semiconductor materials is proposed.

[0014] Therefore, in one aspect the present invention refers to a polymer with the following formula (I):

wherein Ar refers to aromatic ring comprising compounds selected from the group consisting of

R, RL R₂ R3, or R₄ are each independently being hydrogen, halogen, alkyl group, substituted alkyl group, polyether, oligoethylene oxide, polysiloxy, optionally substituted alkenyl, optionally substituted alkynyl, substituted amine, ether, thioether, carbonyl, thiocarbonyl, carboxylic ester, thioester, amide, thioamide, sulfonyl, sulfinyl, wherein at least one of R, R^ R₂, R3, R₄ is not hydrogen

X is independently O, S, or Se.

a and b are 0 or 1 ; x and y are the repeat numbers of two blocks, respectively, with a ratio of between 1 : 10 to 10:1 ,

and x + y vary from about 2 to 1 ,000.

[0015] In a further aspect, the present invention refers to an electronic device comprising an active p-chanel layer of a mixture of at least one polymer of the present invention.

[0016] In still another aspect, the present invention refers to an electronic double layer device comprising a p-channel layer which comprises at least one polymer of the present invention.

[0017] In still another aspect the present invention refers to a method of forming an organic semiconductor device. The method comprises a) providing a substrate; b) depositing a material for preparing an anode electrode; c) forming an anode electrode; d) depositing a solution comprising a mixture of a polymer according to any of the claims 1 to 18 with PCBM; e) depositing a material for preparing a cathode electrode; and f) forming a cathode electrode.

[0018] Other objectives and advantages of the invention will become readily apparent from the following discussion.

[00191 Definitions

[0020] Unless otherwise specified, the below terms used herein are defined as follows:

[0021] As used herein, the term an "aromatic ring" or "aryl" means a monocyclic or polycyclic-aromatic ring or ring radical comprising carbon and hydrogen atoms. Examples of suitable aryl groups include, but are not limited to, phenyl, tolyl, anthacenyl, fluorenyl, indenyl, azulenyl, and naphthyl. An aryl group can be unsubstituted or substituted with one of more substituents (including without limitation alkyl (preferably, lower alkyl or alkyl substituted with one or more halo), hydroxy, alkoxy (preferably, lower alkoxy), alkylsulfanyl, cyano, halo, amino, and nitro. [0022] As used herein, the term "alkyl" means a saturated straight chain or branched non-cyclic hydrocarbon, which are optionally substituted. Alkyl groups included in compounds of this invention may be optionally substituted with one or more substituents. Examples of substituents include, but are not limited to, amino, alkylamino, alkoxy, alkylsulfanyl, oxo, halo, acyl, nitro, hydroxy I, cyano, aryl, alkylaryl, aryloxy, arylsulfanyl, arylamino, carbocyclyl, carbocyclyloxy, carbocyclylthio, carbocyclylamino, heterocyclyl, heterocyclyloxy, heterocyclylamino, heterocyclylthio, and the like. In addition, any carbon in the alkyl segment may be substituted with oxygen (=0), sulfur (=S), or nitrogen.

[0023] The term alkylene refers to an alkyl group or a cycloalkyl group that has two points of attachment to two moieties (e.g., (-CH₂-), -(CH₂CH₂-). Alkylene groups may be substituted or unsubstituted with one or more substituents.

[0024] An aralkyl group refers to an aryl group that is attached to another moiety via an alkylene linker. Aralkyl groups can be substituted or unsubstituted with one or more substituents.

[0025] The term "alkoxy," as used herein, refers to an alkyl group which is linked to another moiety though an oxygen atom. Alkoxy groups can be substituted or unsubstituted with one or more substituents.

[0026] The term "alkylamino," as used herein, refers to an amino group in which one hydrogen atom attached to the nitrogen has been replaced by an alkyl group. The term "dialkylamino," as used herein, refers to an amino group in which two hydrogen atoms attached to the nitrogen have been replaced by alkyl groups, in which the alkyi groups can be the same or different. Alkylamino groups and dialkylamino groups can be substituted or unsubstituted with one or more substituents.

[0027] As used herein, the term "alkenyl" means a straight chain or branched, hydrocarbon radical having at least one carbon-carbon double bond. Alkenyl groups can be substituted; or unsubstituted with one or more substituents. [0028] As used herein, the term "alkynyl" means a straight chain or branched, hydrocarbonon radical typically having from 2 to 10 carbon atoms and having at least one carbon-carbon triple bond. Alkynyl groups can be substituted or unsubstituted with one or more substituents.

[0029] As used herein, the term "halogen" or "halo" means -F, -CI, -Br or -I.

[0030] As used herein, the term "haloalkyl" means an alkyl group in which one or more -H is replaced with a halo group. Examples of haloalkyl groups include, but are not limited to -CF₃, -CHF₂, -CCI₃, -CH₂CH₂Br, -CHaCHiCHzCHaBrJCHs, -CHICH3, or the like. As used herein, the term "haloalkoxy" means an alkoxy group in which one or more -H is replaced with a halo group. Examples of haloalkoxy groups include, but are not limited to -OCF₃ or -OCHF₂.

[0031] The number average (M_n) molecular weight is one way of determining the molecular weight of a polymer. The formula for determining the number average molecular weight M_n is as follows:

_ y ,Ν,Μ,

M„ = ' where Λ/, is the number of molecules of molecular weight M.

[0032] The number average molecular weight of a polymer can be determined by gel permeation chromatography, viscometry via the (Mark-Houwink equation), colligative methods such as vapor pressure osmometry, end-group determination or proton NMR.

[0033] The weight average molecular weight (M_w) is another way of describing the molecular weight of a polymer. Polymer molecules, even if of the same type, come in different sizes (chain lengths, for linear polymers), so that even polymers with the same Mn can have different M_w. The formula for the weight average molecular weight Mw, is given below

M = ^ — - where N, is the number of molecules of molecular weight M.

[0034] The compounds of the invention are defined herein by their chemical structures and/or chemical names. Where a compound is referred to by both a chemical structure and a chemical name, and the chemical structure and chemical name conflict, the chemical structure is determinative of the compound's identity.

[0035] Suitable substituents for an alkyl, alkoxy, alkylsulfanyl, alkylamino, dialkylamino, alkylene, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, aralkyl, heteroaryl, and heteroaralkyl groups include any substituent which will form a stable compound of the invention. Examples of substituents for an alkyl, alkoxy, alkylsulfanyl, alkylamino, dialkylamino, alkylene, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclyl, aryl, aralkyl, heteroaryl, and heteroaralkyl can include but are not limited to an alkyl, an alkoxy, an alkylsulfanyl, an alkylamino, a dialkylamino, an alkenyl, an alkynyl, a cycloalkyl, a cycloalkenyl, a heterocyclyl, an aryl, a heteroaryl, an aralkyl, a heteraralkyl, or a haloalkyl.

[0036] Choices and combinations of substituents and variables envisioned by this invention are only those that result in the formation of stable compounds. The term "stable", as used herein, refers to compounds which possess stability sufficient to allow manufacture and which maintains the integrity of the compound for a sufficient period of time to be useful for the purposes detailed herein (e.g., therapeutic or prophylactic administration to a subject). Typically, such compounds are stable at a temperature of 40°C or less, in the absence of excessive moisture, for at least one week. Such choices and combinations will be apparent to those of ordinary skill in the art and may be determined without undue experimentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 depicts the UV-vis absorption spectra of Polymer 1 to polymer 4 in chlorobenzene. The bandgaps of the polymers determined by the onset absorption are 1.53 to 1.74 eV.

[0038] Figure 2 depicts the cyclic voltammogram of polymer 1 measured in dichloromethane with 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte (scan rate of 100 mV.s ¹). The onset oxidation potential was determined to be 1.04 V, corresponding to HOMO level of -5.44 eV.

[0039] Figure 3 depicts the schematic of the OPV device comprising the blend of polymers 1 , 2, 3 or 4 and PCBM.

[0040] Figure 4 depicts the l-V characteristics of OPV devices based on polymer 1 to polymer 4.

[0041] Figure 5 depicts AFM phase image (height and phase) of polymer 1 and PC₇0BM film (weight ratio: 1 :4). PCBM acts as active layer in the OPV device.

R, R-i , R₂ R3, or R₄ are each independently being, hydrogen, halogen, or alkyl group, substituted alkyl group, polyether, such as oligoethylene oxide, polysiloxy, optionally substituted alkenyl, optionally substituted alkynyl, substituted amine, ether, thioether, carbonyl, thiocarbonyl, carboxylic ester, thioester, amide, thioamide, sulfonyl, sulfinyl, wherein at least one of R, R-i , R₂, R3, R₄ is not hydrogen;

X is independently O, S, or Se.

a and b are 0 or 1 ;

X and y are the repeat numbers of two blocks, respectively. Their ratio can be 1 :10 to 10:1 ;

and x + y vary from about 2 to 1 ,000, or 100 to 500, or 200 to 800, and more specifically, from about 10 to about 100 wherein the number average molecular weight (Mn) of the polymer can be from between about 2,000 to about 1 ,000,000 or from between 5000 to 500,000, or from between 100,000 to 400,000, or from between 200,000 to 800,000. The weight average molecular weight (M_w) of the polymers according to the present invention is from between 4,000 to about 2,000,000 and preferably from about 10,000 to about 1 ,000,000. [0043] In some embodiments, R or or R₂, or R₃, or R₄ which are not hydrogen or halogen have about 10 carbon atoms to about 30 carbon atoms. In some examples, R or Ri which are not hydrogen or halogen may have about 12 to 25 carbon atoms or between 15 to 20 carbon atoms.

[0044] Preferred embodiments can be copolymers of structure (I) wherein number average molecular weight (Mn) of the polymer can be from between about 2,000 to about 1 ,000,000, or from between 5000 to 500,000, or from between 100,000 to 400,000, or from between 200,000 to 800,000. The weight average molecular weight (M_w) of the polymers according to the present invention is from between 4,000 to about 2,000,000 and preferably from about 10,000 to about 1 ,000,000.

[0045] Preferred embodiments of the present invention are illustrated in structures (1) through (6):

wherein,

R, Ri, R₂ R₃, or R₄ are each independently hydrogen, halogen, or alkyl group, substituted alkyl group, polyether, such as oligoethylene oxide, polysiloxy, optionally substituted alkenyl, optionally substituted alkynyl, substituted amine, ether, thioether, carbonyl, thiocarbonyl, carboxylic ester, thioester, amide, thioamide, sulfonyl* sulfinyl, wherein at least one of R, Ri, R₂, R3, 4 is not hydrogen.

[0046] In some examples, R which is not hydrogen or halogen may have about 10 carbon atoms to about 30 carbon atoms; in some examples, R may have of about 12 to 25 carbon atoms; a, b, and c, represent the number of quarterthienylene moieties, and thienylene moieties, a are from 1 to 3; b and c are 0 or 1 ; and

n is the degree of polymerization, and can be from about 2 to 5,000, and more specifically, from about 10 to about 1 ,000 where in the number average molecular weight (Mn) of the polymer can be from 2,000 to about 1 ,000,000, and more specifically, from about 5,000 to about 500,000, or from between 100,000 to 400,000, or from between 200,000 to 800,000; and the weight average molecular weight (Mw) of the polymer can be from 4,000 to about 2,000,000, and more specifically, from about 10,000 to about 1 ,000,000.

[0047] The present invention provides compounds with formula (I) that are particularly useful when employed as semiconductors or charge transport materials in electronic devices such as organic photovoltaic cells, organic thin film field effect transistors (OFETs), or organic light emitting diodes (OLEDs), and the like.

[0048] In particular, the design of the building blocks is as follows:

[0049] Block A is chosen for the construction of light harvest polymers to achieve high Voc, whereas block B is chosen to impart higher mobility to achieve higher Jsc. Additionally, the benzothiadiazole unit is chosen as an electron withdrawing building block to lower the bandgap. [0050] It is a feature of the present invention to provide semiconductor polymers, which have low bandgap of <1 .9 eV (preferable <1.7 eV) but relatively higher Voc (usually > 0.8 V), which covers more broad sunlight spectrum for OPV application and result in high PCE.

[0051] It is another feature of the present invention to provide semiconductor polymers, which can be fabricated into devices with thin film thickness (< 90 nm or <50 nm or <30 hm). This feature offers a promising opportunity to fabricate translucent OPV devices for various applications, such as power generating windows and sunshades.

[0052] In a further feature of the present invention there is provided a class of semiconductor polymers with side chains, preferable branched side chains, attached to the aromatic units with electron rich structures and oligothiophene building unit, which can enhance the solubility and good miscibility with n-type materials, preferably with PCBM (Phenyl-Butyric-Acid-Methyl-Ester), such as PC₆₀BM (Phenyl-C61 -Butyric-Acid-Methyl-Ester or PC₇₀ BM (Phenyl-C₇i-Butyric- Acid-Methyl Ester), alone or in combination with each other to form bi-continuous network structure to facilitate charge separation and charge transporting.

[0053] In a further feature of the present invention there is provided a class of semiconductor polymers with side chains in a regioregular position to facilitate the polymer chains self alignment in the p-channel domains under appropriate processing conditions. Proper molecular alignment can permit higher molecular structural order in thin films, which benefits to efficient charge carrier transport in electronic devices.

[0054] In another aspect, the invention provides an organic semiconductor device comprising a layer of an organic semiconductor material, the organic semiconductor material comprising a compound of formula (I) as defined above.

[0055] Examples of the low bandgap polymers of the present invention are copolymerized fluorene, or dibenzothiophene, or dibenzothiophene sulfone, or benzodithiophene, or dithienothiophene, or cyclopentadithiophene, or dithienosilole, or dibenzosilole, or dibenzothienopyrrole, or dihydroindenofluorene, or naphthalene blocks with oligothiophene and benzothiadiazole units. Such a donor-acceptor (D-A) structure will raise the Voc of the resulting polymer. The key of the design of the D-A structure here is the right choice of the co-monomer blocks, the side chains and also right positioning the side chains to ensure good charge transporting properties of the polymer, good solubility and miscibility with PCBM to achieve good morphology. The film thickness of active layer can be much thinner, such as about 10% or 20% or 30% or 40% or 50% or 60% or 70% or 80% or 90% thinner than commonly used polymers to achieve translucent devices.

[0056] In yet another aspect, the invention provides a method of forming an organic semiconductor device including the steps of providing a substrate, and preparing a solution of a compound of formula (I) mixed with an acceptor, such as PCBM as defined above in a solvent. An organic semiconductor layer is formed on the substrate with the solution.

[0057] The invention also provides a method of forming an active layer containing the low bahdgap polymer and an acceptor, such as PCBM, in a solvent. The active layer possesses a bicontinuous network structure with a domain size <100 nm, preferable <50 nm, more preferably at about 20 to 30 nm.

[0058] Other objects, features, advantages and aspects of the present invention will become apparent to those skilled in the art from the following description and appended claims. It should be understood, however, that the following description, appended claims, and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only.

[0059] Various changes and modifications within the scope of the disclosed invention will become readily apparent to those skilled in the art from reading the following. EXAMPLES

[0060] Exemplary embodiments of methods according to the invention as well as reactants and further processes that may be used are described below.

[0061] Instruments

[0062] 1 H data were performed on a Bruker DPX 400 MHz spectrometer with chemical shifts referenced to internal TMS. Differential scanning calorimetry (DSC) was carried out under nitrogen on a DSC Q100 instrument (scanning rate of lO C.min^"1). Thermal gravimetric analysis (TGA) was carried out using TGA Q500 instrument (heating rate of 10°C.min^"1). Cyclic voltammetry experiments were performed using an Autolab potentiostat (model PGSTAT30) by Echochimie. All CV measurements were recorded in dichloromethane with 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte (scan rate of 100 mV.s^"1). All experiments were performed at room temperature with a conventional three electrode configuration consisting of a platinum wire working electrode, a gold counter electrode, and a Ag/AgCI in 3 M KCI reference electrode. The measured potentials were converted to SCE (saturated calomel electrode) and the corresponding ionization potential (IP) and electron affinity (EA) values were derived from the onset redox potentials, based on -4.4 eV as the SCE energy level relative to vacuum (EA = E_red-onset + 4.4 eV, IP = E_ox-₀nset + 4.4 eV). UV-Vis spectra were recorded on a Shimadzu model 2501 -PC UV-VIS spectrometer.

[0063] Example 1 : Synthesis of monomers 1 and 2

Scheme 1

reaction, or Suzuki coupling reaction, accor ng o t e genera processes depicted in Scheme 1.

[0065] Monomer 1 and 2 possess relatively large bandgap so that when polymerized the resultant polymers possess higher Voc.

[0066] Example 1 (a): Synthesis of monomer 1. 2.7-bis(2-bromothienyl)-9,9- dioctylfluorene

[0067] Monomer 1 can readily be obtained from the Stille coupling reaction of 2,7-dibromo-9,9'-dialkylfluorene with 2-tributylstanyl-thiophene followed by NBS bromination.

[0068] A mixture of 2,7-dibromo-9,9-dioctylfluorene (5.48 g, 10 mmol) and 2- tributylstanyl-thiophene (7.84 g, 21 mmol) was deaerated three times with argon, and then DMF (40 mL) was added. After tetrakis(triphenylphosphine)palladium (Pd(PPh₃)4, (462 mg, 4.0 x 10^"2 mmol) was added, the reaction mixture was stirred for 48 h at 90^°C under dark. After cooling, the reaction mixture was poured into water for extraction with diethyl ether. The combined organic layers were washed with brine and subsequently dried over Na₂S0₄. After the solvent had been removed, the residue, 2,7-bis(2 hienyl)-9,9-dioctylfluorene, was purified by column chromatography on silica gel to afford the target compound as colorless oil with a yield of 88.3% (4.9 g). 1JH NMR (CDCI₂, 400 MHz): δ (ppm) 7.72 (d, 2H), 7.65 (d, 2H), 7.63 (s, 2H), 7.42 (d, 2H), 7.33 (d, 2H), 7.13 (t, 2H), 2.07 (t, 4H), 1.28-1.06 (m, 20H), 0.81 (t, 6H), 0.70 (br, 4H).

[0069] To a stirred solution of 2.0 g of 2,7-bis(2-thienyl)-9,9-dioctylfluorene in 15 mi. CHCI3 at 0°C, a solution of 0.94 g N-bromosuccinimide in 5 ml_ CHCI₃ was added dropwise. The mixture was left at room temperature for 3 hrs. The reaction was quenched by addition of sodium sulfite aqueous solution and the mixture was extracted with CHCI₃ for 3 times and the organic layers were collected. After CHCI₃ was removed off, the crude product was recrystalized in CHCI₃ and ethanol to obtain light yellow solid (2.0 g, 78%). 1 H NMR (CDCI₂, 400 MHz): δ (ppm) 7.71 (d, 2H), 7.55 (d, 2H), 7.52 (s, 2H), 7.17 (d, 2H), 7.10 (d, 2H), 2.04 (t, 4H), 1.20-1.07 (m, 20H), 0.80 (t, 6H), 0.68-0.65 (br, 4H). [00701 Example Kb): Synthesis of monomer 2,2,7-bis(2-bromothienyl)-9,9- dioctyldibenzosilole

[0071] Monomer 2 can be obtained from the similar reaction starting from 2,7- dibromo-9,9-dialkyldibenzosilole. [00721 Synthesis of 4,4'-Dibromo-2,2'-dinitrobiphenyl

[0073] To a stirring solution of 2,5-dibromonitrobenzene (24.0 g, 85.4 mmol) in DMF (1 10 mL) was added copper powder (12.0 g, 188.9 mmol), and the reaction mixture was heated to 125 °C. After 3 h, the mixture was allowed to cool to room temperature. After most of the DMF was evaporated under high vacuum at 60 °C, the mixture was dissolved in toluene (400 mL). The insoluble inorganic salts arid excess copper were next removed by filtration through Celite®. The filtrate was washed with water and 10% NaHC0₃ and evaporated to dryness to yield the crude product as yellow crystals (15.6 g, 91 %). The crude product was next recrystallized from isopropanol to give 1 1.0 g of pure product. The mother liquid was evaporated to one-fourth of its volume and an additional 3.9 g of pure product was recovered, giving a total yield of 14.9 g (87 %). 1 H NMR (CDCI₃): δ (ppm) 7.17 (d, 2H), 7.84 (dd, 2H), 8.39 (d, 2H). [00741 Synthesis of 4.4'-Dibromobiphenyl-2.2'-diamine

[0075] To a solution of 4,4'-Dibromo-2,2'-dinitrobiphenyl (1 1.0 g, 27.4 mmol) in 135 mL of absolute ethanol was added 32 % w/w aqueous HCI (78.0 mL). Tin powder (13.0 g, 108.5 mmol) was then added portionwise over 10 min, and the reaction mixture was heated to reflux at 100 °C for 2 h. After cooling, the mixture was poured into ice water (400 mL) and then made alkaline with 20% w/w aqueous NaOH solution until the pH was 9.0. The product was next extracted with diethyl ether and the organic layer was washed with brine, dried over anhydrous Na₂S0₄, filtered, and then evaporated to dryness to give pure product as light-brown crystals that can be used without further purification (8.6 g, 92%). 1 H NMR (CDCI₃): δ (ppm) 6.92 (s, 6H), 3.78 (br s, 4H, NH₂).

[00761 Synthesis of 4,4'-Dibromo-2,2'-diiodobiphenyl

[0077] A solution of diamine (16.0 g, 46.8 mmol) and concentrated HCI (56.0 mL) in water (64.0 mL) was cooled to 0 °C. Next, 8.0g (1 16 mmol) of NaN0₂ in 40 mL of water was added dropwise to the diamine solution over a period of 30 min, keeping the temperature at 0 °C. After the addition of NaN02 was complete, the resulting mixture was stirred for an additional 30 min. and an aqueous solution of Kl (77.7 g in 150 ml_ of water) at -5 °C was added dropwise over 30 min.

[0078] The reaction mixture was then stirred (by mechanical stirrer) for 1 h at r.t and 3 h at 60 °C, giving a dark brown solution. The solution was then cooled to 25 °C and the brown precipitate was collected by filtration. The crude brown solid was then purified by column chromatography (silica gel, hexane) yielding the title compound as a white solid (7.4 g, 28 % yield). 1 H NMR (CDCI₃): δ (ppm) 7.04 (2H, d), 7.57 (2H, d), 8.1 1 (2H, s).

[0079] Synthesis of 2,7-dibromo-9,9'-di-n-octyldibenzosilole

[0080] n-Butyllithium (17.0 ml_ , 42.5 mmol, 2.5 M in hexane) was added in portions over 2 h to a stirring solution of 4_>4'-dibromo-2,2'-diiodobiphenyl (6.0 g, 10.64 mmol) in dry THF (120 ml_) at -78 °C, under a nitrogen atmosphere. The mixture was next stirred for an additional 1 h at -78 °C. Dichlorodioctylsilane (7.4 ml_, 21.37 mmol) was subsequently added and the temperature of the mixture was raised to room temperature and the mixture was stirred overnight. The reaction mixture was then quenched with distilled water (30.0 ml_), and the solvent was removed under vacuum. The product was then dissolved in diethyl ether and the organic layer washed with brine, dried over anhydrous MgS0₄, filtered, and evaporated in vacuo giving 8.5 g of crude product as brownish oil. Purification by column chromatography (silica gel, hexane) yielded the title compound as colorless oil (4.2 g, 70 % yield) 1 H NMR (CDCI₃): δ (ppm) 0:91 (6H, t), 0. 98 (4H, t), 1 .23-1 .38 (24H, m), 7.53 (2H, dd), 7.63 (2H, d), 7.68 (2H, d).

[0081 ] Synthesis of 2,7-bis(2-thienyl)-9,9-dioctyldibenzosilole

[0082] A mixture of 2,7-dibromo-9,9-dioctyldibenzosilole (0.30 g, 0.548 mmol) and 2-tributylstanylthiophene (0.43 g, 1 .15 mmol) was deaerated three times with argon, and then DMF (5 ml_) was added. After tetrakis(triphenylphosphine)palladium (Pd(PPh₃)4, (12.6 mg, 1 x 10^~2 mmol) was added, the reaction mixture was stirred for 48 h at 90 oC under dark. After cooling, the reaction mixture was poured into water (30 mL) for extraction with diethyl ether. The combined organic layers were washed with brine and subsequently dried over MgS0₄. After the solvent had been removed, the residue was purified by column chromatography on silica gel to afford the title compound as yellowish oil (0.29 g, 93%). 1 H NMR (CD₂CI₂, 400 MHz): δ (ppm) 7.89 (d, 2H), 7.84 (d, 2H), 7.71 (dd, 2H), 7.41 (d, 2H), 7.33 (d, 2H), 7.13 (t, 2H).

[00831 Synthesis of 2,7-bis(2-bromothienyl)-9,9-dioctyldibenzosilole

[0084] To a stirred solution of 2.0 g of 2,7-bis(2-thienyl)-9,9-dioctyldibenzosilole in 15 mL CHCI₃ at 0°C, a solution of 0.91 g N-bromosuccinimide in 5 mL CHCI₃ was added dropwise. The mixture was left at room temperature for 3 hrs. The reaction was quenched by addition of sodium sulfite aqueous solution and the mixture was extracted with CHCI₃ for 3 times and the organic layers were collected. After CHCI₃ was removed off, the crude product was purified by column chromatography on silica gel using hexane as eluent to afford the target compound as white solid (1 .9 g, 72%). 1 H NMR (CDCI₂, 400 MHz): δ (ppm) 7.84 (d, 2H), 7.80 (s, 2H), 7.62 (d, 2H), 7.16 (d, 2H), 7. 09 (d, 2H), 1 .41 -1 .36 (t, 4H), 1 .31-1.18 (m, 20H), 1 .02 (m, 4H), 0.85 (t, 6H).

tolyl)phosphine (7.8 mg, 8% mol) was added in glove-box. Anhydrous chlorobenzene (20 mL) was injected into the mixture by syringe. After heating the mixture at 120°C under nitrogen atmosphere for 48 h, the mixture was poured into stirred methanol. After filtration, the collected solid was purified by Soxhiet extraction with methanol and hexane sequentially. The polymer was then dried under vacuum to give 255 mg of Polymer 1 (88%). Mn = 32200, Mw = 1 16000, PDI = 3.6. 1 NMR (CD₂CI₄, 400 MHz): δ (ppmj 8.20-8.15 (br, 2H), 7.94 (br, 4H), 7.67 (br, 6H), 7.40-7.28 (br, 8H), 7.12 (br, 4H), 2.88 (br, 4H), 2,14 (br, 2H), 1.89 (br, 4H), 1.20-1.07 (br, 88H), 0.94-0.91 (br, 12H), 0.89 (br, 6H). Td of 417 C. [0087] Example 3: Synthesis of polymer 2

2- 2-

octyldodecyl)-2,2':5',2":5",2"'-quaterthiophene (188.5 mg, 0.213 mmol), and 24,7- bis(2-trimethylstannylthien-5-yl)-2, 1 ,3-benzothiadiazole (200 mg, 0.32 mmol), tri(dibenzylideneacetone)dipalladium(0) (5.9 mg, 2% mol) and tri(o- tolyl)phosphine (7.8 mg, 8% mol) was added in glove-box. Anhydrous chlorobenzene (20 mL) was injected into the mixture by syringe. After heating the mixture at 120°C under nitrogen atmosphere for 48 h, the mixture was poured into stirred methanol. After filtration, the collected solid was purified by Soxhiet extraction with methanol and hexane sequentially. The polymer was then dried under vacuum to give 31 1 mg of Polymer 2 (81 %). Td of 385°C.

ee ng rat o:

[00 as that

for example 2, from 2,7-bis(5-bromothiephen-2-yl)-9,9-d octyldibenzosilole (87.3 mg, 0.12 mmol), 5,5"^,-dibromo-3',4"-di(2-octyldodecyl)-2,2':5^,,2":5",2"'- quaterthiophene (106 mg, 0.12 mmol) and 4,7-bis(2-trimethylstannylthien-5-yl)- 2,1 ,3-benzoth!adiazole (150 mg, 0.24 mmol). Yield of 83% is obtained. Td of 380 C.

[0091] Example 5: Synthesis of polymer 4

Pd^dk&k Tri(ivtrtlyl)phofsph!n

C lorobenzene, 120 °C

[0092] dure as examp mmol), 5,5"'-d (153.5

mg, 0.173 mmol) and 4,7-bis(2-trimethylstannylthien-5-yl)-2, 1 ,3-benzothiadiazole (216.6 mg, 0.346 mmol). Yield of 89% is obtained. Td of 276°C. [00931 Example 6: General procedure for OPV device fabrication

[0094] Polymer 1 , 2, 3 and 4 have been used to study the photovoltaic performances by combination with the fullerene, PCBM. Polymer and PCBM were dissolved in dichlorobenzene (weight ratio = 1 : 1 , 1 :2, 1 :4) at a polymer concentration of 10 mg/ml. Patterned ITO-coated glass were used as substrates (with 160 nm of ITO and an average sheet resistance of 14Q/sq). The ITO/glass substrates were cleaned in detergent (30min), distilled water (10min, 2 times), acetone (15 min) and isopropanol (20 min). The substrates were then baked at 60°C to remove residual solvents. A schematic of the device structure is illustrated in FIG. 3. [0095] The dried substrates were subjected to oxygen plasma cleaning for 10 min prior to spin coating a 40 nm of PEDOT SS hole transporting layer followed by baking at 120°C for 10 min. Subsequently, polymer.PCBM blends were spun coat on top of PEDOTPSS layer with a spinning speed of 500 rpm for 120 seconds in inert gas glove box. The metal cathode layer (Ca/Ag) was next evaporated through a shadow mask at a pressure of 8*10^~5 Pa to obtain devices with an active area of 9 mm².

[0096] The performances of the organic solar cells were characterized under simulated AM1.5G solar irradiation with a power intensity of 100 mW/cm².

[0097] Table 1 OPV performance of polymer 1 to polymer 4 blended with PCBM

^■ Active layer

Materials Ratio J_sc (niA/cm²) V_oc (V) FF (%) PCE (%)

thickness (nm)

1 :2 9.74 0.S31 60.9S 4.94 60-65

Polymer 1 :PC70BM

1 :4 9.93 0.S38 . 60,35 5.02 65-70

Polymer 2;PC70BM 1 :2

8.94 0.73S^: 68.41 4.51 75-80 ^'

Polymer 3:PC70BM 1: 1

5.66 0.7S8 52.09 2.32 100-105

Polymer 4:PC70BM 1 :2

S.73 0.610 66.67 3.55 75-80

Claims

substituted amine, ether, thioether, carbonyl, thiocarbonyl, carboxylic ester, thioester, amide, thioamide, sulfonyl, suifinyl, wherein at least one of R, Ri, R₂, R3, R4 is not hydrogen;

X is independently O, S, or Se; a and b are 0 or 1 ; x. and y are the repeat numbers of two blocks, respectively, with a ratio of between 1 :10 to 10:1 ; and x + y vary from about 2 to 1 ,000.

2. The polymer of claim 1 , wherein at least one of R. . F R2, R3, or R₄, is oligoethylene oxide.

3. The polymer of claim 1 , wherein at least one of R, Ri, R₂, R3, or R₄ which is not hydrogen or halogen independently has about 10 carbon atoms to about 30 carbon atoms.

4. The polymer of any one of claims 1 to 3, wherein independently R, R R₂, R3, or R₄ which is not hydrogen or halogen has from about 12 carbon atoms to about 25 carbon atoms.

5. The polymer of any one of claims 1 to 4, wherein x + y varies from about 10 to about 100.

6. The polymer of any one of claims 1 to 5, wherein the number average molecular weight (Mn) of the polymer is from about 2,000 to about 1 ,000,000.

7. The polymer of any one of claims 1 to 6, wherein the Mn of the polymer is from about 5,000 to about 500,000.

8. The polymer of any one of claims 1 to 7, wherein the average molecular weight (Mw) of the polymer is from about 4,000 to about 2,000,000.

9. The polymer of any one of claims 1 to 8, wherein the Mw of the polymer is from about 10,000 to about 1 ,000,000.

10. The olymer of claim 1 having any one of the following structures:

wherein

R and Ri are each independently alkyl, substituted alkyl, alkoxyalkyl, siloxyl-substituted alkyl, perhaloalkyl, polyether, polysiloxy, alkenyl, alkynyl, substituted amine, ether, thioether, carbonyl, thiocarbonyl, carboxylic ester, thioester, amide, thioamide, sulfonyl, sulfinyl; a ratio of x to y is in a range between 1 : 10 to 10: 1 ; and

^■5

x + y is from about 2 to 1 ,000.

1 1 . , The polymer of claim 10, wherein at least one of R or R-_\ is oligoethylene oxide.

0

12. The polymer of claim 10 or 1 1 , wherein R or Ri independently has about 10 carbon atoms to about 30 carbon atoms.

13. The polymer of any one of claims 1 1 and 12, wherein R or has about 125 carbon atoms to about 25 carbon atoms.

14. The polymer of any one of claims 10 to 13, wherein x + y is in a range of 10 to about 100. 0

15. The polymer of any one of claims 10 to 14, wherein the number average molecular weight (Mn) of the polymer is in a range from about 2,000 to about 1 ,000,000.

16. The polymer of any one of claims 10 to 15, wherein Mn of the polymer is in a5 range about 5,000 to about 500,000.

17. The polymer of any one of claims 10 to 16, wherein the weight average molecular weight (M_w) of the polymer is in a range of about 4,000 to about 2,000,000.

18. The polymer of any one of claims 10 to 17, wherein the M_w of the polymer is in a range from 10,000 to about 1 ,000,000.

19. An electronic device comprising an active p-channel layer of a mixture of at least one polymer of any one of claims 1 to 18 with an n-type material.

20. The electronic device according to claim 19 further comprising a hole transporting layer.

21 . An electronic double layer device comprising a p-channel layer which comprises at least one polymer of any one of claims 1 to 18.

22. The electronic device of claim 20, wherein the hole transporting layer is a PEDOT SS polymer.

23. The device of any one of claims 19 to 22, wherein R is alkyl having from about 10 to about 30 carbon atoms.

24. The device of any one of claims 19 to 22, wherein R is alkoxy having from 10 to about 30 carbon atoms.

25. The device of any one of claims 19 to 22, wherein R is carboxylic ester group having from about 10 to about 30 carbon atoms.

26. The device of any one of claims 19 to 22, wherein R is thioether group having from about 10 to about 30 carbon atoms.

27. The device of any one of claims 19 to 22, wherein R is thioesfer group having from about 10 to about 30 carbon atoms.

28. The device of any one of claims 19 to 22, wherein R is amide group having from about 10 to about 30 carbon atoms.

29. The device of any of claims 23 to 28, wherein x + y is from about 5 to about 1 ,000.

30. The device of any one of claims 19 to 23, wherein the side chain R is an alkyl being optionally substituted with a group selected from the group consisting of decyl, undecyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, 2-3,7,7- trimethyloctyl, 2-ethyl-2-propylhexyl, 2-butyloctyl, 2,2-dimethyldecyl, 7-methyl-4- (l-methylethyl)octyl, 2-methyldodecyl, 1 1 -methyldodecyl, 2-ethyldodecyl, 3-ethyldodecyl, 4-ethyldodecyl, 2-butyldecyl, 2-hexyloctyl, 2-pentylnonyl, 4- pentylnonyl, 3,7,1 1 -trimethyldodecyl, 2-butyldodecyl, 1 -methylpentadecyl, 2-hexyldecyl, 2-(1 ,3,3-trimethylbutyl)-5,7,7-trimethyloctyl, 2-hexyldodecyl, 2-octyldecyl, 1 ,1-dimethylhexadecyl, 2-octyldodecyl, 4-octyldodecyl, 2-decyltetradecyl, and 4-decyltetradecyl.

31 . The device of any one of claims 19 to 22, wherein R is an unsubstituted alkyl.

32. The device of any one of claims 19 to 23, wherein R is once or multiply substituted with halogen.

33. The device of any of claims 19 to 23, wherein R is once or multiply substituted with nitrile.

34. The device of any one of claims 19 to 33, comprising the polymer of any of the claims 1 to 18 is mixed with PCBM.

35. The device of claim 30, wherein said PCBM is PC₆oBM or PC₇₀BM.

5 .

36. The device of any one of claims 34 or 35, wherein the ratio between said polymer and PCBM is from 2. to 1 :5.

37. The device of any of claims 19 to 36, comprising a substrate, an anode 10 electrode, a hole transporting layer, an active layer and a cathode electrode.

38. The device of any one of claims 19 to 33, wherein said substrate is a plastic sheet made of a material selected from the group consisting of a polyester, a polycarbonate, and a polyimide.

I 5

39. The device of any one of claims 19 to 34, wherein said substrate is glass.

40. The device of any of claims 19 to 39, wherein the anode electrode comprises indium titanium oxide.

0

41. The device of any of claims 19 to 39, wherein the anode electrode comprises a conductive polymer.

42. The device according to claim 41 , wherein the conductive polymer is 5 polystyrene sulfonate-doped poly(3,4-ethylene dioxythiophene).

43. The device of any of claims 19 to 39, wherein the anode electrode comprises a conductive ink/paste.

44. The device of any of claims 19 to 39, wherein the cathode electrode comprises Al.

45. The device of any of claims 19 to 39, wherein the cathode electrode comprises LiF/AI.

46. The device of any of claims 19 to 39, wherein the cathode electrode comprises or Ca/Ag.

47. The device of any one of claims 19 to 46, wherein said active polymer layer is formed by a method selected from the group consisting of solution processes of spin coating, stamp printing, screen printing, inkjet printing, blade coating, gravure printing, flexo printing and other printing process.

48. The method of preparing the polymers of any one of claims 1 to 18 using a reaction type selected from the group consisting of Stille coupling, Suzuki coupling, reduction, and oxidation reactions.

49. A method of forming an organic semiconductor device including the steps of a) providing a substrate;

b) depositing a material for preparing an anode electrode;

c) forming an anode electrode;

d) depositing a solution comprising a mixture of a polymer according to any of the claims 1 to 18 with PCBM;

e) depositing a material for preparing a cathode electrode; and

f) forming a cathode electrode.

50. The use of the polymers of any one of claims 1 to 18 for p-type organic thin film transistors, or photodiode, or sensors, or memories application.