CN112225882A - N-type polymer containing non-condensed ring acceptor unit and preparation method and application thereof - Google Patents

Abstract

The invention discloses an n-type polymer containing non-condensed ring receptor units, and a preparation method and application thereof. The structural formula of the n-type polymer based on the non-condensed ring acceptor unit is shown as a formula I, wherein a copolymerization unit 1 is an A2-D-A1-D-A2 type non-condensed ring unit, A1 and A2 are electron-deficient units, and D is an electron donor unit; the copolymerization unit 2 is a conjugated aromatic ring unit, and the number n of the repeating units is a natural number of 1-10000. The polymer provided by the invention has relatively low synthesis cost, the synthesis method of each intermediate is simple and easy to purify, the obtained polymer has wide absorption range and high absorption coefficient, better optical absorption complementation and energy level matching can be realized with p-type semiconductor materials, and the polymer has good photoelectric response performance when being applied to organic solar cells.

Description

N-type polymer containing non-condensed ring acceptor unit and preparation method and application thereof

Technical Field

The invention belongs to the technical field of photoelectric materials and application, and particularly relates to an n-type polymer containing a non-condensed ring receptor unit, and a preparation method and application thereof.

Background

In recent years, Polymer Solar Cells (PSCs) have been developed rapidly, and all-polymer solar cells (all-PSCs) using p-type polymers as donors and n-type polymers as acceptors have attracted more and more attention due to advantages of tunable complementary absorption between donors and acceptors, good film stability, and excellent mechanical properties. However, since the number of the high-efficiency polymer donors/acceptors is small, and the problems of micro-phase separation structure of the photovoltaic active layer, non-ideal charge mobility and the like are faced for a long time, the development is slow, and the energy conversion efficiency is behind that of the PSCs using small-molecule materials as acceptors.

Currently, most N-type polymeric acceptor materials are based on imide units, with N2200 being one of the most interesting acceptor materials, but with significant drawbacks: low absorption coefficient (film absorption coefficient at 700nm is only 0.3 x 10)⁵cm^-1) This greatly limits the short-circuit current (J)_sc) Ultimately affecting device performance.

To improve this situation, the li-immortalizing boat teaches that a fused ring non-fullerene acceptor unit (IDIC) is incorporated as a conjugated skeleton into a polymer to design and synthesize PZ1, which has advantages such as high absorptivity, good film-forming property, and thermal stability (angelw. Professor Yanghe, professor Wang Ergang et al also reported in turn polymer acceptors based on IDIC units, all of which exhibited high absorption coefficients, all of which achieved Energy conversion efficiencies (PCEs) of over 10% (ACS Energy Lett.,2019,4,417; Joule,2020,4,658). Then, professor yellow fei introduces another fused ring non-fullerene acceptor unit (Y5) as a conjugated skeleton into the polymer, designs and synthesizes PJ1, obtains 14.4% PCE, and further highlights the development potential of the all-polymer solar cell (Nano Energy,2020,72, 104718).

However, the synthesis cost of the fused ring non-fullerene acceptor unit is high, and large-area commercial production is not facilitated. Research on the literature finds that some small molecule non-fullerene receptors based on non-condensed ring structures show high absorptivity and good device performance, and meanwhile, the synthesis steps are relatively short, the synthesis cost is relatively low, and the work of introducing non-condensed ring receptor units into n-type polymers as conjugated backbones is not reported at present. Therefore, it is desired to design and synthesize a novel non-condensed ring-containing polymeric monomer by using such a construction method, and to adjust absorption and energy levels of a polymer by selecting different copolymerization units, and to obtain a highly efficient all-polymer solar cell.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide an n-type polymer containing non-condensed ring acceptor units, a preparation method thereof and an expanded application of the n-type polymer as an acceptor material in an all-polymer solar cell.

The purpose of the invention is realized by the following technical scheme.

The polymer provided by the invention is an n-type polymer obtained by copolymerizing a non-fused ring acceptor unit and other conjugated aromatic ring units.

The invention provides an n-type polymer containing non-condensed ring acceptor units, which has a structural general formula shown as a formula I:

in the formula I, the copolymerized unit 1 is a non-condensed ring unit of A2-D-A1-D-A2 type, and is represented by a formula II:

in formula ii, the a1 unit is selected from any one of the following structural formulas:

wherein R1 in the structural formula of A1 is independently selected from H, halogen, straight-chain or branched-chain alkyl or alkoxy or alkylthio or alkylsilyl with 1-50 carbon atoms, or aryl substituted by alkyl; the alkyl in the alkyl-substituted aryl can be a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F, Cl or I; the dotted line in the structural formula a1 represents the attachment site to the D unit;

in formula II, the D unit is selected from any one of the following structural formulas:

wherein R2 in the structural formula D is independently selected from H, halogen, straight chain or branched chain alkyl or alkoxy or alkylthio with 1-50 carbon atoms, or alkylsilyl or alkyl substituted aryl; the alkyl in the alkyl-substituted aryl can be a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F, Cl or I; in the structural formula, X represents C, O or S atom; the dashed lines in the D structure indicate the attachment sites to the a1 and a2 units;

in formula ii, the a2 unit is selected from any one of the following structural formulas:

the dotted line in the structural formula of a 2: indicating the connection site of the A2 unit and the D unit; ② represents a linking site of A2 unit and the copolymerizing unit 2;

in the formula I, the copolymerization unit 2 is a conjugated aromatic ring unit and is selected from any one of the following structural formulas:

wherein R in the structural formula of the copolymerization unit 2 is independently selected from H, halogen, straight-chain or branched-chain alkyl or alkoxy or alkylthio with 1-50 carbon atoms, or alkylsilyl or alkyl-substituted aryl; the alkyl in the alkyl-substituted aryl can be a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F or Cl; in the structural formula, X represents C, O or S atom; in the structural formula, Y represents H, F or Cl atom; the dotted line in the structural formula of the copolymerization unit 2 represents a connection site with the copolymerization unit 1;

wherein n is the number of the polymer repeating units and is a natural number of 1-10000.

Further, one structure of the copolymerization unit 1 is shown as a formula III:

wherein R1 in the formula III is as defined for R1 in the A1 unit, and R2 is as defined for R2 in the D unit; the dotted line in said formula III indicates the attachment site to the copolymerizing unit 2.

Further, the polymer in the formula I is shown as a formula IV:

wherein R1 in the formula IV is defined as R1 in the unit A1, and R2 is defined as R2 in the unit D; n is a natural number of 1 to 10000.

Further, the number of carbon atoms of the alkyl straight chain and the branched chain of the polymer is 1-50.

The invention provides a method for preparing the n-type polymer containing the non-condensed ring acceptor unit, which comprises the following steps:

under the inert gas atmosphere, mixing the monomer of the copolymerization unit 1 and the monomer of the copolymerization unit 2 in a reaction solvent in a molar ratio of 1:1 for polymerization reaction, and purifying to obtain the copolymer; the reaction solvent comprises at least one of toluene, o-xylene or chlorobenzene; the catalyst comprises a palladium catalyst; the reaction temperature of the polymerization reaction is 100-120 ℃, the reaction time is 12-16 h, and the stirring speed is 500-1000 rpm; the mixing mode is physical blending; the purification mode comprises one or more of filtration, column chromatography and Soxhlet extraction dialysis.

The n-type polymer containing the non-condensed ring acceptor unit provided by the invention can be used as an acceptor material to be applied to preparation of all-polymer solar cells.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention designs a kind of n-type polymer material containing non-condensed ring receptor unit;

(2) the preparation method provided by the invention has the advantages of simple process, high yield, low manufacturing cost, suitability for industrial production and the like;

(3) the polymer obtained by the invention takes A2-D-A1-D-A2 configuration monomer as a core, so that the intramolecular charge transfer effect of the whole molecule is enhanced, and the polymer is beneficial to obtaining wide absorption and high light absorption coefficient;

(4) the n-type polymer containing the non-condensed ring acceptor unit provided by the invention can be applied to the field of organic photovoltaics.

Drawings

FIG. 1 is a diagram of a synthetic scheme embodying non-fused ring unit based monomer BTzC-IC-Br and n-type conjugated polymer materials PBTzC-IC-T and PBTzC-IC-TT.

FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of monomer BTzC-IC-Br based on non-condensed ring units.

FIG. 3 is a NMR carbon spectrum of monomer BTzC-IC-Br based on non-fused ring units.

FIG. 4 shows the absorption spectra of solution and thin film of n-type polymer material PBTzC-IC-T based on non-condensed ring unit.

FIG. 5 is a structural diagram of a donor material PBDB-T in an active layer and a structural diagram of a solar cell device.

FIG. 6 is a voltage-current density curve of an all-polymer solar cell with PBDB-T and PBTzC-IC-T as active layers.

FIG. 7 is a graph of wavelength-external quantum efficiency of an all-polymer solar cell with PBDB-T and PBTzC-IC-T as active layers.

Detailed Description

The following description of the embodiments of the present invention is provided in connection with the accompanying drawings and examples, but the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art.

The practice of the present invention may employ conventional techniques of polymer chemistry within the skill of the relevant art. In the following examples, efforts are made to ensure accuracy with respect to numbers used (including amounts, temperature, reaction time, etc.) but some experimental errors and deviations should be accounted for. The temperatures used in the following examples are expressed in degrees Celsius and the pressures are at or near atmospheric. All solvents used were either analytically pure or chromatographically pure, and all reactions were carried out under an inert gas atmosphere. All reagents were obtained commercially unless otherwise indicated.

By way of example, the structural formula of the n-type polymer containing non-fused ring acceptor units prepared in the following examples is shown below:

wherein n is a natural number, and the value of n is 1-10000.

Example 1

Preparation of polymerized monomer BTzC-IC-Br

The chemical synthesis route of BTzC-IC-Br is shown as follows, and the specific reaction steps and reaction conditions are as follows:

(1) the starting materials 1 and 2 and the terminal compound 4 were prepared according to the Methods reported in the literature (synthetic references of starting material 1: J. Mater. chem. C,2015,3, 2792-2797; ACS appl. Polym. Mater.,2019,1, 2302-2312. synthetic references of starting material 2: Small Methods,2019,1900531; ACS appl. Mater. Interfaces,2020,12, 16531-16540. synthetic references of Compound 4: Eur. J. Org.chem.,2016, 2404-2412; J. Am. chem. Soc.,2017,139,1336-1343), and other reagents required for each reaction were purchased commercially.

(2) Synthesis of Compound 3

Raw material 1(325mg), raw material 2(500mg), pivalic acid (54mg), cesium carbonate (138mg), tris (o-methoxyphenyl) phosphine (35mg), tris (dibenzylideneacetone) dipalladium (55mg) were sequentially added to a 40ml pressure bottle, and then 15ml o-xylene was added, and the temperature was raised to 125 ℃ under nitrogen protection to react for 24 hours. After the reaction, dichloromethane was used for extraction, and the crude product was purified by column chromatography to obtain 444mg of compound 3 with a yield of 64%.

(3) Synthesis of BTzC-IC-Br

Compound 3(444mg), compound 4(372mg), and pyridine (1.5ml) were sequentially added to a 100ml two-necked flask, followed by addition of 30ml of chloroform, and the reaction was carried out at room temperature for 6 hours under nitrogen atmosphere. After the reaction is finished, a large amount of trichloromethane is removed in a spinning mode, then the trichloromethane is settled in methanol, and the precipitated solid is collected and purified through column chromatography separation, so that 566mg of monomer BTzC-IC-Br is obtained, and the yield is 91%. (the hydrogen spectrum of the monomer BTzC-IC-Br is shown in figure 2, and the carbon spectrum of the monomer BTzC-IC-Br is shown in figure 3)

Example 2

Preparation of Polymer PBTzC-IC-T

The chemical synthesis route of PBTzC-IC-T is shown as follows, and the specific reaction steps and reaction conditions are as follows:

(1) the polymerized monomer 5, the catalyst tetrakis (triphenylphosphine) palladium and o-xylene were all commercially available.

(2) Synthesis of Polymer PBTzC-IC-T

The monomers BTzC-IC-Br (0.10mmol, 182.33mg), monomer 5(0.10mmol, 40.98mg) were dissolved in o-xylene (5mL), followed by the addition of tetrakis (triphenylphosphine) palladium (0.002mmol, 2.31mg), degassed with nitrogen gas, stirred at 110 ℃ for 12 hours, cooled to room temperature, followed by the addition of 2- (tributyltin) thiophene for 2 hours, followed by the addition of 2-bromothiophene for 2 hours. After cooling to room temperature, the polymer was precipitated in methanol, then placed in a soxhlet extractor, extracted with methanol, acetone, n-hexane, dichloromethane respectively, and finally the resulting dichloromethane fraction was concentrated, precipitated in methanol, filtered, and dried to yield 167mg of polymer, 96% yield.

Example 3

Preparation of Polymer PBTzC-IC-TT

The chemical synthesis route of PBTzC-IC-TT is shown as follows, and the specific reaction steps and reaction conditions are as follows:

(1) polymerized monomer 6, the catalyst tetrakis (triphenylphosphine) palladium and o-xylene were all commercially available.

(2) Synthesis of Polymer PBTzC-IC-TT

The monomers BTzC-IC-Br (0.08mmol, 145.86mg), monomer 6(0.08mmol, 37.27mg) were dissolved in o-xylene (4mL), after which tetrakis (triphenylphosphine) palladium (0.0016mmol, 1.85mg) was added, degassed with nitrogen gas, stirred at 110 ℃ for 12 hours, cooled to room temperature, reacted with 2- (tributyltin) thiophene for 2 hours, followed by 2-bromothiophene for 2 hours. After cooling to room temperature, the polymer was precipitated in methanol, and then placed in a soxhlet extractor, and extracted with methanol, acetone, n-hexane, dichloromethane, and chloroform, respectively, the residue was dissolved by heating with chlorobenzene, the chlorobenzene fraction obtained by heat filtration was concentrated, precipitated in methanol, filtered, and dried to obtain 108mg of polymer with a yield of 75%.

Example 4

The polymer material obtained in example 2 is used for representing PBTzC-IC-T as an example to illustrate the application of the polymer material as a polymer receptor in an all-polymer solar cell device

The following examples illustrate the proposed n-type conjugated polymers based on non-fused ring acceptor units and their application in organic opto-electronic devices, but the invention is not limited to these examples.

The specific preparation process of the device is as follows:

and (3) a 40nm PEDOT (polymer ethylene terephthalate) (PSS) hole transport layer is spin-coated on the ITO, then a mixed optical active layer of a polymer donor PBDB-T and PBTzC-IC-T with the thickness of about 100nm is spin-coated, then quaternary ammonium bromide salt (PFN-Br) of amido polyfluorene with the thickness of about 5nm is spin-coated to be used as a cathode interface layer, and then an Ag layer with the thickness of 100nm is vapor-deposited, so that the preparation of the device is completed.

The polymer solar cell sequentially comprises a transparent conductive anode, an anode interface layer, a polymer/polymer active layer, a cathode interface layer and a cathode from bottom to top (the cell structure is shown in figure 5). The voltage-current density curve test (see figure 6) and the wavelength-external quantum efficiency curve test (see figure 7) were carried out, and the device performance parameters are shown in table 1. As can be seen from the test results, the all-polymer solar cell device with PBTzC-IC-T as the receptor can obtain higher energy conversion efficiency, and the wide absorption range and high absorption coefficient of the material (see figure 4) show the potential application value of the n-type polymer based on the non-condensed ring receptor unit as the receptor material in the all-polymer solar cell material.

TABLE 1 device parameters of all-polymer solar cell based on PBDB-T/PBTzC-IC-T as active layer

The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (5)

1. An n-type polymer containing non-condensed ring acceptor units is characterized in that the structural general formula is shown as formula I:

in the formula I, the copolymerized unit 1 is a non-condensed ring unit of A2-D-A1-D-A2 type, and is represented by a formula II:

in the formula II, A1 unit is selected from any one of the following structural formulas:

wherein R1 in the structural formula of A1 is independently selected from H, halogen, straight-chain or branched-chain alkyl or alkoxy or alkylthio or alkylsilyl with 1-50 carbon atoms, or aryl substituted by alkyl; the alkyl in the alkyl-substituted aryl is a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F, Cl or I; the dotted line in the structural formula a1 represents the attachment site to the D unit;

in the formula II, the D unit is selected from any one of the following structural formulas:

wherein R2 in the structural formula D is independently selected from H, halogen, straight chain or branched chain alkyl or alkoxy or alkylthio with 1-50 carbon atoms, or alkylsilyl or alkyl substituted aryl; the alkyl in the alkyl-substituted aryl is a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F, Cl or I; in the structural formula, X represents C, O or S atom; the dashed lines in the D structure indicate the attachment sites to the a1 and a2 units;

in the formula II, A2 unit is selected from any one of the following structural formulas:

the dotted line in the structural formula of a 2: indicating the connection site of the A2 unit and the D unit; ② represents a linking site of A2 unit and the copolymerizing unit 2;

in the formula I, a copolymerization unit 2 is a conjugated aromatic ring unit and is selected from any one of the following structural formulas:

wherein R in the structural formula of the copolymerization unit 2 is independently selected from H, halogen, straight-chain or branched-chain alkyl or alkoxy or alkylthio with 1-50 carbon atoms, or alkylsilyl or alkyl-substituted aryl; the alkyl in the alkyl-substituted aryl is a straight chain or branched chain alkyl with the carbon atom number of 1-50, and the aryl is a benzene ring or a thiophene ring; the halogen is F or Cl; in the structural formula, X represents C, O or S atom; in the structural formula, Y represents H, F or Cl atom; the dotted line in the structural formula of the copolymerization unit 2 represents a connection site with the copolymerization unit 1;

wherein n is the number of the polymer repeating units and is a natural number of 1-10000.

2. The polymer of claim 1, wherein one of the copolymerized units 1 is represented by formula iii:

wherein R1 in the formula III is as defined for R1 in the A1 unit, and R2 is as defined for R2 in the D unit; the dotted line in said formula III indicates the attachment site to the copolymerizing unit 2.

3. The polymer of claim 1 or 2, wherein one of the polymers of formula i has the structure of formula iv:

wherein R1 in the formula IV is defined as R1 in the unit A1, and R2 is defined as R2 in the unit D; n is a natural number of 1 to 10000.

4. A process for preparing a polymer of formula i according to any one of claims 1 to 3, comprising the steps of:

under the inert gas atmosphere, mixing the monomer of the copolymerization unit 1 and the monomer of the copolymerization unit 2 in a reaction solvent in a molar ratio of 1:1 for polymerization reaction, and purifying to obtain the copolymer; the reaction solvent comprises at least one of toluene, o-xylene or chlorobenzene; the catalyst comprises a palladium catalyst; the reaction temperature of the polymerization reaction is 100-120 ℃, the reaction time is 12-16 h, and the stirring speed is 500-1000 rpm; the mixing mode is physical blending; the purification mode comprises one or more of filtration, column chromatography and Soxhlet extraction dialysis.

5. Use of the n-type polymers containing non-fused ring acceptor units as claimed in claims 1 to 4 as acceptor materials in organic solar cells.

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