CN114560999B

CN114560999B - Boron-nitrogen coordination bond-based n-type macromolecular compound and preparation method and application thereof

Info

Publication number: CN114560999B
Application number: CN202210403733.4A
Authority: CN
Inventors: 刘俊; 曹旭; 田洪坤; 王利祥
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2022-04-18
Filing date: 2022-04-18
Publication date: 2024-03-12
Anticipated expiration: 2042-04-18
Also published as: CN114560999A

Abstract

Based on boron nitrogenAn n-type macromolecular compound with coordination bonds, a preparation method and application thereof, belonging to the technical field of macromolecular functional materials and electronics. Solves the technical problem of low mobility of the organic conjugated polymer compound in the prior art. The conjugated main chain of the high molecular compound contains two fragments, namely a diboron nitrogen coordination bond bridged bipyridine unit and an Ar unit which are in electron deficiency, and the structural formula is shown as the formula (I). The high molecular compound has the characteristics of good planeness, small single bond connection proportion, strong skeleton rigidity and intermolecular interaction and the like, and can greatly improve the electron mobility of the material; ar structure is a condensed unit, the chemical structure is easy to modify, the energy level structure is adjustable, the steric hindrance is small, and the planarity is good; can be applied as a charge transport layer material of an organic field effect transistor.

Description

Boron-nitrogen coordination bond-based n-type macromolecular compound and preparation method and application thereof

Technical Field

The invention belongs to the technical field of high molecular functional materials and organic electronics, and particularly relates to an n-type high molecular compound based on boron-nitrogen coordination bonds, and a preparation method and application thereof.

Background

The conjugated polymer semiconductor material can be used as a novel charge transmission material due to the advantages of flexibility, low cost and the like, and particularly an organic field effect transistor constructed by taking a polymer semiconductor as a charge transmission layer has been widely focused by people due to the potential application prospect of the conjugated polymer semiconductor material in flexible devices and wearable electronics. Polymeric semiconductor materials can be classified into p-type materials (hole transport), n-type materials (electron transport) and bipolar materials (both electron and hole transport) according to the type of carrier transport. With current research, p-type materials are widely studied and develop faster, and some materials have mobilities far exceeding the level of amorphous silicon. In contrast, n-type and bipolar materials develop more slowly, have low mobility, and have poor air stability. In view of the application of bipolar materials and n-type materials in organic logic complementary circuits, the development of high mobility bipolar materials and n-type materials is the current focus of research.

In addition, the organic conjugated polymer can be applied to the conductive material through physical or chemical doping of the material. The conductive polymer is a polymer material which has pi conjugated main chain structure and can realize intrinsic conductive property by doping, such as polyaniline, polypyrrole and the like. The conductive polymer not only can realize the conductive property similar to metal, but also has the plastic property of the conventional polymer material, such as flexibility, light weight, low-cost solution processing and the like. The conductivity of the conductive polymer can be continuously adjusted in a wide scale by controlling the doping degree, so that the conductive polymer has the property of a semiconductor or a conductor. However, the core of the research of the materials is the problem of carrier transmission of the organic conjugated polymer, so how to effectively improve the carrier mobility, especially the electron mobility, of the organic conjugated polymer becomes an important problem of whether the materials can be applied.

Disclosure of Invention

In view of the above, the invention provides an n-type polymer compound based on boron-nitrogen coordination bonds, a preparation method and application thereof, and aims to solve the technical problems in the prior art and further improve the carrier mobility of an organic conjugated polymer compound.

The technical scheme adopted by the invention for solving the technical problems is as follows.

The invention provides an n-type high molecular compound based on boron-nitrogen coordination bond, which has a structure shown in a formula (I):

in the formula (I), n is an integer of 2-1000; m is an integer of 0 to 10, and two m are the same or different; x is an integer of 1 to 20, y is an integer of 1 to 20, and x and y are the same or different; ar-isa is O, S or Se, b is CH or N, and c is F, cl or CN.

Preferably, the-Ar-is one of the following structures:

the invention also provides a preparation method of the n-type high polymer compound based on boron-nitrogen coordination bond, which comprises the following steps:

under the protection of inert atmosphere, dissolving a dibromo monomer of a bis (boron-nitrogen) coordination bond bridged bipyridine, a bis (trimethyltin) monomer and tetra (triphenylphosphine) palladium in an organic solvent, performing a Stille polymerization reaction under the conditions of light shielding and heating reflux, and purifying the obtained polymer after the Stille polymerization reaction is finished to obtain an n-type high polymer compound based on the boron-nitrogen coordination bond;

The structural formula of the dibromo monomer of the double boron-nitrogen coordination bond bridged bipyridine is as follows;

the structural formula of the ditrimethyltin monomer is as follows:

preferably, the organic solvent is toluene, and the concentration of the dibromo monomer and the concentration of the bistrimethyltin monomer of the bisborazine coordination bond bridged bipyridine in the organic solvent are respectively 0.005-0.1 mM.

Preferably, the mass ratio of the dibromo monomer, the ditrimethyltin monomer and the tetra (triphenylphosphine) palladium of the bis-boron-nitrogen coordination bond bridged bipyridine is 1:1:0.04.

Preferably, the Stille polymerization reaction temperature is 110-120 ℃ and the reaction time is 1-96 h.

The invention also provides the application of the n-type macromolecular compound based on boron-nitrogen coordination bonds as a charge transport layer material of an organic field effect transistor,

the electron mobility of the charge transport layer material in the organic field effect transistor is 0.1cm ² V ^-1 s ^-1 The above.

Preferably, the structure of the organic field effect transistor is a top gate bottom contact or a bottom gate top contact;

the top gate bottom contact structure comprises a substrate, a source electrode, a drain electrode, a charge transmission layer, a dielectric layer and a gate electrode; the material of the substrate is Si/SiO ₂ Substrate, siO ₂ The thickness is 300nm; the source electrode and the drain electrode are made of gold, and the thickness is 10-40 nm; the thickness of the charge transport layer is 1-100 nm; the dielectric layer is made of PMMA and has a thickness of 500nm; the gate electrode is made of gold, and the thickness is 50-90 nm;

The bottom gate top contact structure comprises a substrate, a source electrode, a drain electrode and a charge transmission layer; the material of the substrate is Si/SiO ₂ Substrate, siO ₂ The thickness is 300nm; the source electrode and the drain electrode are made of gold, and the thickness is 10-40 nm; the thickness of the charge transport layer is 1-100 nm.

The invention also provides application of the n-type high polymer compound based on boron-nitrogen coordination bonds in organic conductor materials and organic thermoelectric materials after doping.

Compared with the prior art, the invention has the beneficial effects that:

1. the n-type high molecular compound based on boron-nitrogen coordination bonds has the characteristics of good planarity, skeleton rigidity and strong intermolecular interaction, and the conjugated main chain only comprises two repeating units which are respectively BNBP units and derivative units of benzodithiophene, so that the proportion of single bond connection among the units can be reduced to the greatest extent, and the energy disorder caused by chain distortion is reduced. By introducing N heteroatoms in the benzodithiophene units, steric hindrance between units can be reduced, and chain conformation can be optimized so as to improve molecular accumulation and improve transmission performance. In addition, electron-deficient substituents can be introduced into the 1,4 benzene rings to regulate and control the energy level structure of the polymer in a wide range, so that the polymer has adjustable LUMO/HOMO energy level and can further regulate and control the carrier transmission characteristic. BNBP units are electron-deficient units, so that the LUMO energy level of the polymer is relatively low, and the polymer is suitable for being used as an n-type or bipolar transmission material of an organic field effect transistor; by doping, the polymer can be applied to organic conductor materials and organic thermoelectric materials.

2. According to the n-type high molecular compound based on boron-nitrogen coordination bonds, the pre-aggregation behavior and solid stacking property of the high molecules in the solution can be regulated and controlled by changing the-Ar-unit and the substituent group thereof, so that the crystallization property of the material is optimized, the transmission property of the material is improved, and higher electron mobility is facilitated.

3. The n-type high molecular compound based on boron-nitrogen coordination bond is used as a charge transport material of an organic field effect transistor, and the electron mobility is 0.1cm ² V ^-1 s ^-1 The above.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is an ultraviolet-visible absorption spectrum of the polymer P-BNBP-BBtz (C28) of example 1;

FIG. 2 is an electrochemical test curve of the polymer P-BNBP-BBtz (C28) of example 1;

FIG. 3 is an out-of-plane grazing incidence X-ray diffraction test curve of the polymer P-BNBP-BBtz (C28) of example 1;

FIG. 4 is an electrochemical test curve of the polymer P-BNBP-BBtz (C28) of example 13;

fig. 5 is a block diagram of an organic field effect transistor device of a top gate bottom contact structure (TGBC);

fig. 6 is a block diagram of an organic field effect transistor device of a Bottom Gate Top Contact (BGTC);

fig. 7 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 21;

fig. 8 is an n-type output characteristic of the polymer organic field effect transistor device of example 21.

Fig. 9 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 22;

fig. 10 is an n-type output characteristic of the polymer organic field effect transistor device of example 22;

fig. 11 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 23;

fig. 12 is an n-type output characteristic of the polymer organic field effect transistor device of example 23;

fig. 13 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 24;

fig. 14 is an n-type output characteristic of the polymer organic field effect transistor device of example 24;

fig. 15 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 25;

Fig. 16 is an n-type output characteristic of the polymer organic field effect transistor device of example 25;

fig. 17 is an n-type transfer characteristic of the organic field effect transistor device of example 26;

fig. 18 is an n-type output characteristic of the organic field effect transistor device of example 26;

fig. 19 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 27;

fig. 20 is an n-type output characteristic of the polymer organic field effect transistor device of example 27;

fig. 21 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 28;

fig. 22 is an n-type output characteristic of the polymer organic field effect transistor device of example 28;

fig. 23 is an n-type transfer characteristic of the polymer organic field effect transistor device of example 29;

fig. 24 is an n-type output characteristic of the polymer organic field effect transistor device of example 29;

fig. 25 is an n-type transfer characteristic of the organic field effect transistor device of example 30;

fig. 26 is an n-type output characteristic of the organic field effect transistor device of example 30.

Detailed Description

In order to further illustrate the invention, preferred embodiments of the invention are described below in connection with specific embodiments, but it should be understood that these descriptions are merely intended to further illustrate the features and advantages of the invention and are not limiting of the patent claims of the invention.

The n-type high molecular compound based on boron-nitrogen coordination bonds has two structural units in a repeating unit, namely a double boron-nitrogen coordination bond bridged pyridine unit (BNBP) and an-Ar-unit, and the structure is shown as a formula (I):

in the formula (I), n is an integer of 2-1000, m is an integer of 0-10, alkyl side chains on nitrogen atoms on two sides are the same or different, x is an integer of 1-20, y is an integer of 1-20, and x and y are the same or different; ar-is of the structurea is O, S or Se, b is CH or N, and c is F, cl or CN.

In the above technical scheme, it is preferable that-Ar-is one of the following structures:

in the invention, the electronic structure of the n-type polymer compound based on boron-nitrogen coordination bonds can be effectively regulated by changing the structure of-Ar-, so that a polymer with proper energy level and solid state accumulation can be obtained. Through experimental detection, the inventionThe polymer of (C) has proper LUMO energy level, relatively planar skeleton, strong pre-aggregation in solution state, and high electron mobility (electron mobility is 0.1 cm) ² V ^-1 s ^-1 The thickness can reach 0.12-0.43cm ² V ^-1 s ^-1 ，0.17-0.43cm ² V ^-1 s ^-1 ，0.2-0.43cm ² V ^-1 s ^-1 ，0.24-0.43cm ² V ^-1 s ^-1 ，0.39-0.43cm ² V ^-1 s ^-1 ，0.40-0.43cm ² V ^-1 s ^-1 ,0.41-0.43cm ² V ^-1 s ^-1 ) Can be used as electron transport material in organic field effect transistor.

The n-type polymer compound based on boron-nitrogen coordination bond is prepared by Stille-type reaction, and the preparation method can be as follows:

Under the protection of inert atmosphere (generally argon), BNBP dibromo monomer, ditrimethyltin monomer, tetra (triphenylphosphine) palladium and cuprous iodide (cocatalyst) are dissolved in toluene solution according to the mass ratio of 1:1:0.04:0.1, the dissolution sequence is not particularly limited, tetra (triphenylphosphine) palladium is added after that, the concentration of BNBP dibromo monomer and ditrimethyltin monomer can be respectively 0.005-0.1 mM, reflux is carried out for 1-96 h at 110-120 ℃ under the condition of light shielding, stille polymerization reaction is carried out, and after the reaction is finished, the obtained polymer is purified to obtain n-type macromolecular compound based on boron nitrogen coordination bond;

the reaction formula is as follows:

the purification method of the n-type high molecular compound based on boron-nitrogen coordination bond prepared by the method can be as follows: the reaction product system was cooled to room temperature and then dropped into a pure methanol solvent to obtain a precipitated solid. And then washing the precipitated solid with acetone, normal hexane and chloroform solvent in turn to remove the catalyst and the oligomer by using a Soxhlet extractor, then carrying out hot dissolution with chlorobenzene, filtering while the solution is hot, removing most of the organic solvent by rotary evaporation, and finally settling the viscous solution in methanol to obtain the n-type high polymer compound based on boron-nitrogen coordination bonds.

The n-type high molecular compound based on boron-nitrogen coordination bonds can be applied as a charge transport layer material of an organic field effect transistor, the application method of the charge transport layer material in the organic field effect transistor is not particularly limited, and the n-type high molecular compound based on boron-nitrogen coordination bonds can be used according to the using method of the conventional charge transport layer material in the field. The structure of the organic field effect transistor is not particularly limited, and the structure in the prior art is applicable, and high electron mobility can be achieved by using the charge transport layer material. In the prior art, the structure of the organic field effect transistor may be either Top Gate Bottom Contact (TGBC) or Bottom Gate Top Contact (BGTC). As shown in fig. 5, the device with the TGBC structure sequentially comprises a substrate, a source electrode, a drain electrode, a charge transport layer, a dielectric layer and a gate electrode from bottom to top. As shown in fig. 6, the device of the BGTC structure sequentially comprises a substrate, a gate electrode, a charge transport layer, and a source/drain electrode from bottom to top. The material of the substrate can be Si/SiO ₂ Substrate, siO ₂ The thickness is 300nm; the source and drain electrodes can be made of gold with the thickness of 10-40 nm, and are usually obtained by adopting an evaporation mode; the charge transport layer is made of n-type high molecular compound based on boron-nitrogen coordination bond, the thickness is 1-100 nm, and the material is usually obtained by spin coating; the material of the dielectric layer is PMMA, the thickness is 500nm, and the dielectric layer is usually obtained by spin coating; the gate electrode is gold with a thickness of 50-90 nm, and is usually obtained by deposition.

The invention also provides application of the n-type macromolecular compound doped with the boron-nitrogen coordination bond in organic conductor materials and organic thermoelectric materials.

The invention is further illustrated below with reference to examples.

Example 1

P-BNBP-BBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (64.5 mg,0.05 mmol), benzodithiazole bisstannum salt (27.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg,0.002 mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 64mg and 96%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.79; h,9.63; b,1.72; f,6.05; n,6.69; s,5.11. Experimental value C,69.97; h,9.62; n,6.61; s,5.02.

Subjecting the polymer to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis to obtain M _n ＝61186，PDI＝1.94。

The polymer P-BNBP-BBtz (C28) prepared in example 1 was subjected to ultraviolet-visible absorption spectrum analysis, electrochemical test and out-of-plane grazing incidence X-ray diffraction test, and the test results are shown in FIG. 1, FIG. 2 and FIG. 3, respectively. As can be seen from FIG. 1, the film of the polymer P-BNBP-BBtz (C28) presents a sharp ultraviolet-visible light absorption spectrum, which indicates that the skeleton is relatively rigid; as can be seen from FIG. 2, the LUMO/HOMO energy level of the polymer P-BNBP-BBtz (C28) is-3.80/-6.04 eV, which shows that the polymer can be used as an electron transport material; from FIG. 3, it can be seen that the polymer P-BNBP-BBtz (C28) adopts a hybrid orientation in a solid state, and the pi-pi stacking distance is only 0.36nm, which indicates that the polymer of the invention can realize high electron mobility.

Example 2

P-BNBP-BBtz (C32) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (66.9 mg,0.05 mmol), benzodithiazole bisstannum salt (27.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg,0.002 mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 63mg and 94%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,72.18; h,10.24; b,1.55; f,5.44; n,6.01; s,4.59. Experimental value C,72.21; h,10.35; n,6.09; s,4.49.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis, yielding Mn=14392, PDI=2.37.

Example 3

P-BNBP-BBtz (C24) polymer, the structural formula is shown as follows (in the structural formula, a terminal group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (55.6 mg,0.05 mmol), benzodithiazole bisstannum salt (27.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg,0.002 mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 52mg and 90%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,69.21; h,9.33; b,1.89; f,6.63; n,7.34; s,5.60. Experimental value C,69.18; h,9.35; n,7.35; s,5.56.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=28106, pdi=1.88.

Example 4

The P-BNBP-2fBDT (C28) polymer has the following structural formula (in the structural formula, the end capping group is omitted):

the preparation method comprises the following steps: BNBP dibromo monomer (64.5 mg,0.05 mmol), difluorobenzodithiophene bisstannum salt (27.6 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol) are added into a baked clean polymerization bottle, then the system is vacuumized and aerated with argon to exchange gas for a plurality of times, distilled toluene solvent (1 mL) is added under a dark state, after reflux for 48h at 120 ℃, the reaction system is settled in methanol while the reaction system is hot, high molecules are separated out, the precipitate is washed out of the small molecules and the catalyst by a Soxhlet extractor by acetone and normal hexane in sequence, and finally the high molecules are extracted by chloroform. The yield was 60mg and 89%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.99; h,9.62; b,1.64; f,8.64; n,4.25; s,4.86. The experimental value is C,70.95; h,9.65; n,4.27; s,4.85.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃ C.): mn=48156, pdi=1.72.

Example 5

The P-BNBP-2fBDT (C32) polymer has the following structural formula (in the structural formula, the end capping group is omitted):

the preparation method comprises the following steps: BNBP dibromo monomer (66.9 mg,0.05 mmol), difluorobenzodithiophene bisstannum salt (27.6 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol) are added into a baked clean polymerization bottle, then the system is vacuumized and aerated with argon to exchange gas for a plurality of times, distilled toluene solvent (1 mL) is added under a dark state, after reflux for 48h at 120 ℃, the reaction system is settled in methanol while the reaction system is hot, high molecules are separated out, the precipitate is washed out of the small molecules and the catalyst by a Soxhlet extractor sequentially by acetone and normal hexane, and finally the high molecules are extracted by chloroform. The yield was 68mg and 95%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,72.14; h,10.00; b,1.51; f,7.96; n,3.91; s,4.48. Experimental value C,72.19; h,9.96; n,3.93; s,4.50.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃ C.): mn=67842, pdi=1.73.

Example 6

The P-BNBP-2fBDT (C24) polymer has the following structural formula (in the structural formula, the end capping group is omitted):

The preparation method comprises the following steps: BNBP dibromo monomer (55.6 mg,0.05 mmol), difluorobenzodithiophene bisstannum salt (27.6 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol) are added into a baked clean polymerization bottle, then the system is vacuumized and aerated with argon to exchange gas for a plurality of times, distilled toluene solvent (1 mL) is added under a dark state, after reflux for 48h at 120 ℃, the reaction system is settled in methanol while the reaction system is hot, high molecules are separated out, the precipitate is washed out of the small molecules and the catalyst by a Soxhlet extractor by acetone and normal hexane in sequence, and finally the high molecules are extracted by chloroform. The yield was 51mg, 86%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,69.25; h,9.06; b,1.83; f,9.67; n,4.75; s,5.44. Experimental value C,69.30; h,9.11; n,4.76; s,5.41.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃ C.): mn=48126, pdi=1.89.

Example 7

P-BNBP-2CNBDT (C28) polymer with the following structural formula (in the structural formula, the end sealing group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (64.5 mg,0.05 mmol), dicyanobenzodithiophene bisstannum salt (28.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 59mg and 91%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,71.76; h,9.42; b,1.66; f,5.82; n,6.44; s,4.91. Experimental value C,71.70; h,9.45; n,6.41; s,4.93. The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃ C.): mn=32557, pdi=1.76.

Example 8

P-BNBP-2CNBDT (C32) polymer with the following structural formula (in the structural formula, end sealing group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (66.9 mg,0.05 mmol), dicyanobenzodithiophene bisstannum salt (28.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 63mg and 89%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,72.85; h,9.81; b,1.52; f,5.36; n,5.93; s,4.52. Experimental value C,72.83; h,9.82; n,5.91; s,4.50. The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃ C.): mn=44366, pdi=1.52.

Example 9

P-BNBP-2CNBDT (C24) polymer with the following structural formula (in the structural formula, the end sealing group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (55.6 mg,0.05 mmol), dicyanobenzodithiophene bisstannum salt (28.3 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 54mg and 91%. .

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.45; h,8.95; b,1.81; f,6.37; n,7.04; s,5.37. Experimental value C,70.44; h,8.89; n,7.06; s,5.41.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=28997, pdi=1.63.

Example 10

P-BNBP-2fBBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, a terminal blocking group is omitted):

The preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (64.5 mg,0.05 mmol), difluorobenzodithiazole distannium salt (27.7 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, the polymer was precipitated, the precipitate was washed out with acetone and n-hexane in order, and the small molecule and catalyst were finally extracted with chloroform. The yield was 63mg and 97%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,68.71; h,9.35; b,1.67; f,8.81; n,6.50; s,4.96. Experimental value C,68.71; h,9.40; n,6.48; s,4.97.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=48777, pdi=1.49.

Example 11

P-BNBP-2fBBtz (C32) polymer, the structural formula is shown as follows (in the structural formula, a terminal blocking group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (66.9 mg,0.05 mmol), difluorobenzodithiazole distannium salt (27.7 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 64mg and 92%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.06; h,9.75; b,1.54; f,8.11; n,5.98; s,4.56. Experimental value C,70.10; h,9.71; n,5.99; s,4.51.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=58891, pdi=2.01.

Example 12

The P-BNBP-2fBBtz (C32') polymer has the following structural formula (in the structural formula, the end capping group is omitted):

the preparation method comprises the following steps: to the baked clean polymerization flask were added BNBP dibromo monomer (66.9 mg,0.05 mmol), difluorobenzodithiazole distannium salt (27.7 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol), then the system was evacuated and purged with argon gas for several times, distilled toluene solvent (1 mL) was added in a dark state, after refluxing at 120℃for 48 hours, the reaction system was settled in methanol while hot, high molecules were separated out, the precipitate was washed out with acetone and n-hexane in order, and finally the high molecules were extracted with chloroform. The yield was 67mg and 95%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.06; h,9.75; b,1.54; f,8.11; n,5.98; s,4.56. Experimental value C,70.11; h,9.73; n,5.96; s,4.53.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=42877, pdi=1.52.

Example 13

P-BNBP-2CNBBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the preparation method comprises the following steps: BNBP dibromo monomer (64.5 mg,0.05 mmol), difluorobenzodithiazole distannium salt (28.4 mg,0.05 mmol), cuprous iodide (1.0 mg,0.005 mmol) and tetrakis (triphenylphosphine) palladium (2.4 mg, 0.002mmol) are added into a baked clean polymerization bottle, then the system is vacuumized and ventilated for many times by argon, distilled toluene solvent (1 mL) is added in a dark state, after reflux is carried out at 120 ℃ for 48h, the reaction system is settled in methanol while the reaction system is hot, high molecules are separated out, a Soxhlet extractor is used for washing out small molecules and catalysts by acetone and normal hexane in sequence, and finally the high molecules are extracted by chloroform. The yield was 57mg and 87%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,69.81; h,9.25; b,1.65; f,5.81; n,8.57; s,4.90. Experimental value C,69.85; h,9.21; n,8.59; s,4.93.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=33517, pdi=1.48.

The P-BNBP-2CNBBtz (C28) polymer prepared in example 13 was subjected to electrochemical test, and the test results are shown in FIG. 4. As can be seen from FIG. 4, the LUMO/HOMO energy level of the polymer P-BNBP-2CNBBtz (C28) is-4.36/-6.04 eV, which shows that the polymer can be used as an electron transport material.

Example 14

P-BNBP-fBBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the P-BNBP-fBBtz (C28) polymer was prepared in the same manner as in example 1. Except that the benzodithiazole distannate was replaced with a monofluorobenzodithiazole distannate. The high molecular yield was 59mg and 93%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,69.68; h,9.56; b,1.69; f,7.45; n,6.59; s,5.03. Experimental value C,69.61; h,9.57; n,6.61; s,5.06.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=46180, pdi=1.72.

Example 15

P-BNBP-CNBBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the P-BNBP-CNBBtz (C28) polymer was prepared as in example 1. Except that the benzodithiazole distannate was replaced with a monocyano benzodithiazole distannate. The high molecular yield was 58mg and the yield was 90%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,70.24; h,9.51; b,1.69; f,5.93; n,7.64; s,5.00. Experimental value C,70.26; h,9.50; n,7.70; s,5.04.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis, to give Mn=44369, PDI=1.82.

Example 16

P-BNBP-CNBBSez (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing group is omitted):

the P-BNBP-CNBBSez (C28) polymer was prepared as in example 1. Except that the benzodithiazole distannate was replaced with a monocyano benzodiselenazole distannate. The high molecular yield was 65mg and 94%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,65.45; h,8.86; b,1.57; f,5.52; n,7.12; se,11.47. Experimental value C,65.44; h,8.88; n,7.10.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) to give Mn=32758 and PDI=1.69.

Example 17

P-BNBP-2CNBBSez (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing group is omitted):

the P-BNBP-2CNBBSez (C28) polymer was prepared as in example 1. Except that the benzodithiazole distannate was replaced with dicyanobenzodiselenole distannate. The high molecular yield was 66mg and 95%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,65.14; h,8.63; b,1.54; f,5.42; n,8.00; se,11.27. Experimental value C,65.11; h,8.67; n,7.95.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) to give Mn=27358 and PDI=1.87.

Example 18

P-BNBP-2fBBSez (C28) polymer, the structural formula is shown as follows (in the structural formula, the end capping group is omitted):

the P-BNBP-2fBBSez (C28) polymer was prepared as in example 1. Except that the benzodithiazole distannate was replaced with a difluorobenzodiselenole distannate. The high molecular yield was 57mg and 82%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,64.07; h,8.72; b,1.56; f,8.22; n,6.06; se,11.38. Experimental value C,64.17; h,8.67; n,6.11.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=47878, pdi=2.11.

Example 19

P-BNBP-2ClBBtz (C28) polymer, the structural formula is shown as follows (in the structural formula, end sealing groups are omitted):

the P-BNBP-2ClBBtz (C28) polymer was prepared in the same manner as in example 1. Except that the benzodithiazole distannate was replaced with a dichlorobenzodithiazole distannate. The high molecular yield was 58mg and 88%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,67.01; h,9.12; b,1.63; cl,5.35; f,5.73; n,6.34; s,4.83. Experimental value C,67.05; h,9.06; n,6.30.

The polymer thus prepared was subjected to gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis, to give Mn=78542 and PDI=1.85.

Example 20

P-BNBP-2ClBBSez (C28) polymer, the structural formula is shown as follows (in the structural formula, end capping group is omitted):

the P-BNBP-2ClBBSez (C28) polymer was prepared in the same manner as in example 1. Except that the benzodithiazole distannate was replaced with a dichlorobenzodiselenazol distannate. The high molecular yield was 63mg and 89%.

The prepared polymer was subjected to elemental analysis, and the results were as follows: calculated as C,62.58; h,8.52; b,1.52; cl,4.99; f,5.35; n,5.92; se,11.12. Experimental value C,62.52; h,8.55; n,6.01.

Gel permeation chromatography (GPC, trichlorobenzene, polystyrene standard, 150 ℃) analysis of the polymer produced gave mn=54278, pdi=1.55.

Example 21

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field effect transistor device was fabricated using the polymer P-BNBP-BBtz (C28) of example 1 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-BBTz(C28)(30nm)/PMMA(500nm)/Au(80nm)。

Performance test was performed on the organic field effect transistor device of example 21, fig. 7 is a transfer characteristic curve of the polymer transistor device, and fig. 8 is an output characteristic curve of the polymer transistor device. Using the boron-nitrogen coordination bond-based n-type polymer compound of the present invention as a charge transport material, the electron mobility of the material calculated from the transfer characteristic curve was 0.12cm ² v _- ¹ s ^-1 。

Example 22

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field effect transistor device was fabricated using the polymer P-BNBP-BBtz (C32) of example 2 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-DTBX(100nm)/PMMA(500nm)/Au(80nm)。

Performance test was performed on the organic field effect transistor device of example 22, fig. 9 shows an n-type transfer characteristic of the polymer transistor device, and fig. 10 shows an n-type output characteristic of the polymer transistor device. Using the boron-nitrogen coordination bond-based n-type polymer compound of the present invention as a charge transport material, the electron mobility of the material calculated from the transfer characteristic curve was 0.41cm ² v ^-1 s ^-1 。

Example 23

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: the polymer P-BNBP-2fBBtz (C32) of example 11 was used as an electric power The charge transmission layer is used for preparing an organic field effect transistor device, and the structure of the device is Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-2fBBTz(C32)(40nm)/PMMA(500nm)/Au(80nm)。

Performance test was performed on the organic field effect transistor device of example 23, fig. 11 is an n-type transfer characteristic curve of such a polymer transistor device, and fig. 12 is an n-type output characteristic curve of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.20cm ² V ^-1 s ^-1 。

Example 24

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device was fabricated using the polymer P-BNBP-2fBBtz (C32') of example 12 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-2fBBTz(C32’)(20nm)/PMMA(500nm)/Au(80nm)。

Performance tests were performed on the organic field effect transistor device of example 24, fig. 13 shows an n-type transfer characteristic of such a polymer transistor device, and fig. 14 shows an n-type output characteristic of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.43cm ² V ^-1 s ^-1 。

Example 25

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device was fabricated using the polymer P-BNBP-2CNBBtz (C28) of example 13 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-2CNBBTz(C28)(30nm)/PMMA(500nm)/Au(80nm)。

Performance test of the organic field effect transistor device of example 25, FIG. 15 shows n-type transfer characteristic of the polymer transistor device, and FIG. 16 showsThe n-type output characteristic curve of the high polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.41cm ² V ^-1 s ^-1 。

Example 26

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device was fabricated using the polymer P-BNBP-2fBBSez (C28) of example 18 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/P-BNBP-2fBBSez(C28)(30nm)/Au(40nm)。

Performance tests were performed on the organic field effect transistor device of example 26, fig. 17 shows an n-type transfer characteristic of such a polymer transistor device, and fig. 18 shows an n-type output characteristic of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.39cm ² V ^-1 s ^-1 。

Example 27

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device was fabricated using the polymer P-BNBP-2fBDT (C28) of example 4 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-2fBDT(C28)(30nm)/PMMA(500nm)/Au(80nm)。

Performance test was performed on the organic field effect transistor device of example 27, fig. 19 is an n-type transfer characteristic curve of such a polymer transistor device, and fig. 20 is an n-type output characteristic curve of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.17cm ² V ^-1 s ^-1 。

Example 28

Based on boron-nitrogen complexesUse of a bit-bonded n-type polymeric compound as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device was fabricated using the polymer P-BNBP-2fBDT (C32) of example 5 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/Au(25nm)/P-BNBP-2fBDT(C32)(30nm)/PMMA(500nm)/Au(80nm)。

Performance tests were performed on the organic field effect transistor device of example 28, and fig. 21 shows an n-type transfer characteristic curve of such a polymer transistor device, and fig. 22 shows an n-type output characteristic curve of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.24cm ² V ^-1 s ^-1 。

Example 29

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field-effect transistor device having a structure of Si/SiO was fabricated using the polymer P-BNBP-2fBDT (C24) of example 5 as the charge transport layer ₂ (300nm)/Au(25nm)/P-BNBP-2fBDT(C24)(30nm)/PMMA(500nm)/Au(80nm)。

Performance tests were performed on the organic field effect transistor device of example 29, fig. 23 shows an n-type transfer characteristic curve of such a polymer transistor device, and fig. 24 shows an n-type output characteristic curve of such a polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.41cm ² V ^-1 s ^-1 。

Example 30

Use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material for organic field effect transistor devices: an organic field effect transistor device was fabricated using the polymer P-BNBP-2CNBDT (C24) of example 9 as the charge transport layer, the device structure was Si/SiO ₂ (300nm)/P-BNBP-2CNBDT(C24)(30nm)/Au(40nm)。

For example 30Performance test of airport effect transistor device, fig. 25 shows n-type transfer characteristic of such polymer transistor device, and fig. 26 shows n-type output characteristic of such polymer transistor device. Description of the use of the boron-nitrogen coordination bond-based n-type Polymer of the present invention as a Charge transport Material, the electron mobility of the Material calculated from the transfer characteristic Curve was 0.40cm ² V ^-1 s ^-1 。

Example 21-example 30 illustrates that the n-type polymer compound based on boron-nitrogen coordination bond of the present invention can regulate its charge transport type by adjusting the-Ar-unit.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims

1. The n-type macromolecular compound based on boron-nitrogen coordination bonds is characterized by having a structure shown in a formula (I):

in the formula (I), n is an integer of 2-1000; m is an integer of 0 to 10, and two m are the same or different; x is an integer of 1 to 20, y is an integer of 1 to 20, and x and y are the same or different;

the-Ar-is one of the following structures:

2. the method for producing an n-type polymer compound according to claim 1, wherein the method comprises the steps of:

the structural formula of the ditrimethyltin monomer is as follows:

3. the method for producing an n-type polymer compound based on boron-nitrogen coordination bonds according to claim 2, wherein the organic solvent is toluene, and the concentration of the dibromo monomer and the bistrimethyltin monomer of the bisboron-nitrogen coordination bond bridged bipyridine in the organic solvent is 0.005 to 0.1mM, respectively.

4. The method for producing an n-type polymer compound based on boron-nitrogen coordination bonds according to claim 2, wherein the ratio of the amounts of the substances of the dibromo monomer, the ditrimethyl tin monomer, and the tetrakis (triphenylphosphine) palladium of the bis-boron-nitrogen coordination bond bridged bipyridine is 1:1:0.04.

5. The method for producing an n-type polymer compound based on boron-nitrogen coordination bonds according to claim 2, wherein the Stille polymerization reaction is carried out at a reaction temperature of 110 to 120 ℃ for a reaction time of 1 to 96 hours.

6. The method for preparing the n-type macromolecular compound based on boron-nitrogen coordination bonds according to claim 2, wherein the Stille polymerization reaction is further added with a cocatalyst of cuprous iodide, and the mass ratio of the cuprous iodide to the dibromo monomer of the diboron-nitrogen coordination bond bridged bipyridine is 0.1:1.

7. The use of an n-type polymer compound based on boron-nitrogen coordination bonds as claimed in claim 1 as a charge transport layer material for organic field effect transistors, characterized in that: the electron mobility of the charge transport layer material in the organic field effect transistor is 0.1cm ² V ^-1 s ^-1 The above.

8. The use of an n-type polymer compound based on boron-nitrogen coordination bonds as a charge transport layer material of an organic field effect transistor according to claim 7, wherein the structure of the organic field effect transistor is top gate bottom contact or bottom gate top contact;

9. The use of an n-type polymer compound based on boron-nitrogen coordination bonds as claimed in claim 1, after doping, in organic conductor materials and organic thermoelectric materials.