阅读说明：本技术 一种基于吡啶的d-a型交叉共轭聚合物、其制备和应用 (Pyridine-based D-A type cross-conjugated polymer, and preparation and application thereof ) 是由 李忠安 孙祥浪 于 2020-12-17 设计创作，主要内容包括：本发明属于有机光电高分子材料领域,公开了一种基于吡啶的给体-受体(donor-acceptor,D-A)型交叉共轭聚合物、其制备和应用,该交叉共轭聚合物的结构如通式(A)所示,该交叉共轭聚合物以异聚三炔作为主链骨架结构,以苯胺类取代芴作为侧链基团,以3,5-二取代吡啶作为电子受体基团；其中,R为苯胺类给电子基团,n取值为10-30的整数。本发明通过引入吸电子基团吡啶,对交叉共轭聚合物的主链结构进行优化,对应得到的D-A型交叉共轭聚合物空穴迁移率显著提升,尤其可作为非掺杂空穴传输材料应用于反式平面结构钙钛矿太阳能电池中(可获得超过22％的高能量转化效率)。(The invention belongs to the field of organic photoelectric high molecular materials, and discloses a pyridine-based donor-acceptor (D-A) type cross conjugated polymer, and preparation and application thereof, wherein the structure of the cross conjugated polymer is shown as a general formula (A), the cross conjugated polymer takes hetero-poly-triyne as a main chain skeleton structure, aniline substituted fluorene as a side chain group, and 3, 5-disubstituted pyridine as an electron acceptor group; wherein R is aniline electron-donating group, and n is an integer of 10-30. According to the invention, the electron-withdrawing group pyridine is introduced to optimize the main chain structure of the cross conjugated polymer, so that the hole mobility of the correspondingly obtained D-A type cross conjugated polymer is remarkably improved, and the D-A type cross conjugated polymer can be particularly used as a non-doped hole transport material to be applied to a trans-planar perovskite solar cell (the high energy conversion efficiency of over 22 percent can be obtained).)

1. A D-A type cross conjugated polymer based on pyridine is characterized in that the structure of the D-A type cross conjugated polymer is shown as a general formula (A), the donor-receptor type cross conjugated polymer takes hetero-poly-triyne as a main chain skeleton structure, aniline substituted fluorene as a side chain group, and 3, 5-disubstituted pyridine as an electron acceptor group;

wherein R is aniline electron-donating group, and n is an integer of 10-30.

2. The pyridine-based D-A type cross-conjugated polymer according to claim 1, wherein the aniline electron-donating group is one selected from diphenylamine, 4' -dimethyldiphenylamine, 4' -dimethoxydiphenylamine, 3' -dimethoxydiphenylamine, phenothiazine, 9, 10-dihydro-9, 9-dimethylacridine, triphenylamine, 4' -dimethyltriphenylamine, 4' -dimethoxytriphenylamine, 2-p-phenyl (4-vinylphenyl) amine, 2-p-tolyl (4-vinylphenyl) amine, 2-p-methoxyphenyl (4-vinylphenyl) amine, and 1-naphthylaminobenzene; preferably 4,4' -dimethyldiphenylamine.

3. The preparation method of the pyridine-based D-A type cross-conjugated polymer according to claim 1 or 2, wherein the pyridine-based D-A type cross-conjugated polymer is obtained by a Sonagashira coupling reaction of an aniline-substituted fluorenylene intermediate and 3, 5-diethynylpyridine, wherein the aniline-substituted fluorenylene intermediate has a structure shown as a formula (I):

wherein R is aniline electron donating group.

4. The preparation method according to claim 3, wherein the preparation method comprises: mixing and dissolving the aniline substituted fluorenylene intermediate and 3, 5-diacetylene pyridine in an organic solvent, adding a catalyst, organic base and cuprous iodide under the protection of inert atmosphere, heating to reflux, fully reacting, adding methanol for filtering, drying the obtained solid, removing the solvent, performing Soxhlet extraction, and drying to obtain the pyridine-based D-A type cross conjugated polymer.

5. The preparation method according to claim 3, wherein the molar ratio of the aniline-substituted fluorene alkene intermediate to the 3, 5-diacetylene pyridine is 1: 1-1: 1.1.

6. The method of claim 3, wherein the reaction time is 60 to 72 hours.

7. Use of the pyridine-based D-A type cross-conjugated polymer according to claim 1 or 2 as a hole transport material.

Technical Field

The invention belongs to the field of organic photoelectric high polymer materials, and particularly relates to a pyridine-based donor-acceptor (D-A) type cross conjugated polymer, and preparation and application thereof.

Background

Since the first perovskite solar cell appeared in 2009, with the continuous improvement of the cell preparation level and the discovery of new materials, the energy Conversion Efficiency (PCE) of the perovskite solar cell has been improved from the first 3.8% to 25.5% in the last decade, and the increase range is even more than the development of many solar cells for decades. However, the commercialization of these materials still faces many challenges, the most prominent of which comes from device stability, including both instability of the perovskite material itself and instability of the charge transport layer. For the hole transport layer, currently, most commonly used Hole Transport Materials (HTMs) such as 2,2,7, 7-tetrakis [ N, N-bis (4-methoxyphenyl) amino ] -9, 9-spirobifluorene (Spiro-omatad) and poly [ bis (4-phenyl) (2,4, 6-trimethylphenyl) amine ] (PTAA) and the like need to be enhanced by chemical doping because intrinsic hole mobility and conductivity are not high. However, the introduced ion dopants such as lithium bistrifluoromethanesulfonimide (LiTFSI) and 4-tert-butylpyridine (tBP) are not only very moisture-absorbing, but also have a very complex oxidation process, which accelerates the degradation of the perovskite material and leads to rapid degradation of the battery performance. Therefore, the development of highly efficient and stable undoped hole transport materials with dopant removal is currently an important research direction in this field.

Recently, researchers at home and abroad have made certain research progress in the aspect of organic non-doped HTMs. However, the development of organic non-doped HTMs still faces some challenges: 1) most non-doped HTMs have poor hole mobility, resulting in significant gap between device efficiency and doped devices; 2) the stability of undoped devices is far from practical use. Therefore, the development of a novel undoped hole transport material with high mobility and high stability is important for the future development of the perovskite battery.

The inventor of the invention researches and obtains an isopoly triene cross-conjugated polymer, and preparation and application thereof (see Chinese patent document CN111019094), the isopoly triene cross-conjugated polymer is used as a non-doped hole transport material to be applied to a trans-planar perovskite solar cell, and the highest photoelectric conversion efficiency reachesTo 19.33% (the highest photoelectric conversion efficiency corresponds to the structural formula shown in the following formula P1). Although this research result solves the above problems to some extent, the hole mobility of the P1 material is only 1.85 × 10^-6cm²V^-1s^-1The application range of the material is limited to a certain extent, and the photoelectric conversion efficiency of the material applied to the solar cell is expected to be further improved. Due to the strong electron push-pull effect, D-A type molecules generally have larger dipole moment, and strong molecular acting force can be formed between dipoles, thereby being beneficial to improving the charge transmission capability of the material.

Disclosure of Invention

In view of the above-identified deficiencies in the art or needs for improvement, it is an object of the present invention to provide a pyridine-based donor-acceptor (D-A) type cross-conjugated polymer, its preparation and use, wherein the main chain structure of the cross conjugated polymer is optimized by introducing pyridine with electron-withdrawing group, uses hetero-poly-triyne as a polymer main chain skeleton structure, uses anilines substituted fluorene as a side chain group, uses 3,5 disubstituted pyridine as an electron acceptor unit, the hole mobility of the correspondingly obtained D-A type cross conjugated polymer is remarkably improved, and the D-A type cross conjugated polymer can be particularly applied to the photoelectric field as a non-doped hole transport material (for example, the D-A type cross conjugated polymer can be applied to a trans-planar perovskite solar cell as a non-doped hole transport material, and can obtain high energy conversion efficiency of over 22%), therefore, the technical problem that the intrinsic hole mobility of the high-molecular hole transport material in the prior art is not high is solved. The cross conjugated polymer of the invention can especially take 3, 5-diethynylpyridine as an electron acceptor group and 4,4' -dimethyldiphenylamine substituted fluorene as a side chain group, and the introduction of the pyridine group leads the hole mobility of the material to reach 1.92 multiplied by 10^{- 3}cm²V^-1s^-1Similar materials with benzene rings as linking groups (P1, 1.85X 10)^-6cm²V^-1s^-1) The improvement is close to 1000 times.

In order to achieve the above object, according to one aspect of the present invention, there is provided a pyridine-based D-a type cross-conjugated polymer, characterized in that the structure thereof is represented by general formula (a), the donor-receptor type cross-conjugated polymer has hetero-triyne as a main chain skeleton structure, anilines substituted fluorene as a side chain group, and 3, 5-disubstituted pyridine as an electron acceptor group;

wherein R is aniline electron-donating group, and n is an integer of 10-30.

Further preferably, the aniline electron-donating group is one selected from diphenylamine, 4' -dimethyldiphenylamine, 4' -dimethoxydiphenylamine, 3' -dimethoxydiphenylamine, phenothiazine, 9, 10-dihydro-9, 9-dimethylacridine, triphenylamine, 4' -dimethyltriphenylamine, 4' -dimethoxytriphenylamine, 2-p-phenyl (4-vinylphenyl) amine, 2-p-tolyl (4-vinylphenyl) amine, 2-p-methoxyphenyl (4-vinylphenyl) amine and 1-naphthylaminobenzene; preferably 4,4' -dimethyldiphenylamine.

According to another aspect of the present invention, the present invention provides a preparation method of the pyridine-based D-a type cross-conjugated polymer, wherein the pyridine-based D-a type cross-conjugated polymer is obtained by performing a Sonagashira coupling reaction between an aniline-substituted fluorenylene intermediate and 3, 5-diethynylpyridine, wherein the aniline-substituted fluorenylene intermediate has a structure represented by formula (i):

wherein R is aniline electron donating group.

As a further preferred aspect of the present invention, the preparation method specifically comprises:

mixing and dissolving the aniline substituted fluorenylene intermediate and 3, 5-diacetylene pyridine in an organic solvent, adding a catalyst, organic base and cuprous iodide under the protection of inert atmosphere, heating to reflux, fully reacting, adding methanol for filtering, drying the obtained solid, removing the solvent, performing Soxhlet extraction, and drying to obtain the pyridine-based D-A type cross conjugated polymer.

In a further preferred embodiment of the present invention, the molar ratio of the aniline-substituted fluorenylene intermediate to 3, 5-diethynylpyridine is 1:1 to 1: 1.1.

In a further preferred embodiment of the present invention, the reaction time is 60 to 72 hours.

According to still another aspect of the present invention, there is provided the use of the above-mentioned pyridine-based D-A type cross-conjugated polymer as a hole transporting material.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a pyridine-based D-A type cross conjugated polymer, which takes hetero-poly-triyne as a main chain skeleton structure of the polymer, aniline substituted fluorene as a side chain group, pyridine as a connecting group, and the introduction of an electron-withdrawing group pyridine reduces the Highest Occupied Molecular Orbital (HOMO) energy level of the material on one hand, obviously enhances the electron-withdrawing effect of molecules on the other hand, and improves the hole mobility of the material. At present, no report is made on using pyridine as a connecting group of a non-doped polymer hole transport material, and the method is helpful for solving the problem of low hole mobility of the current non-doped polymer hole transport material.

(2) The aniline electron-donating group R in the general formula (A) of the invention is 4,4' -dimethyldiphenylamine, and the corresponding obtained pyridine-based D-A type cross-conjugated polymer (shown as the following formula PPY) has the hole mobility of 1.92 multiplied by 10^-3cm²V^-1s^-1Hole mobility is improved over similar materials (formula P1 above) in which the benzene ring is the linking groupNearly 1000 times (hole mobility of only 1.85 × 10 for P1 material)^-6cm² V^-1s^-1). For example, when PPY is applied to a trans-planar perovskite solar cell as an undoped hole transport material, the illumination intensity is 100mW cm^-2Under the irradiation condition of simulated sunlight AM1.5G, the highest photoelectric conversion efficiency can reach 22.41 percent, which is higher than that of a comparative PTAA device.

(3) The D-A type cross conjugated polymer provided by the invention can be obtained by performing Sonagashira coupling reaction on a dibromo-substituted fluorenene intermediate and 3, 5-diacetylene pyridine, and the preparation method is simple and easy to implement.

(4) The D-A type cross conjugated polymer based on pyridine provided by the invention can be directly used as a hole transport material to be applied to a trans-planar perovskite solar cell, and a dopant or an additive is not required to be added for chemical doping, so that the long-term stability of a device is prevented from being damaged by the introduction of the dopant and the additive. The pyridine-based D-A type cross conjugated polymer provided by the invention is a high-efficiency and high-stability undoped hole transport material. It should be noted that, it can be reasonably inferred from the relevant properties of the series of materials that the series of materials can also be applied to other devices in the photoelectric field as hole transport materials, such as electroluminescent devices, organic solar cells and the like.

Drawings

FIG. 1 is a scheme for the synthesis of PPY of example 1.

FIG. 2 shows the nuclear magnetic hydrogen spectrum of PPY of example 1.

FIG. 3 is an ultraviolet-visible absorption spectrum of the PPY film of example 1.

FIG. 4 is a cyclic voltammogram of PPY from example 1.

FIG. 5 is a hole mobility test chart of PPY in example 1.

Fig. 6 is a graph comparing the J-V curve of the optimum device for the trans-planar perovskite cell with PPY as the undoped hole transport material of example 2 with poly [ bis (4-phenyl) (2,4, 6-trimethylphenyl) amine ] (PTAA).

Fig. 7 shows the device efficiency variation curve of the perovskite cell with the trans-planar structure and the PPY as the undoped hole transport material in the embodiment 2 under the continuous illumination condition.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a D-A type cross conjugated polymer based on pyridine, which takes hetero-poly-triyne as a main chain skeleton structure of the polymer, aniline substituted fluorene as a side chain group and pyridine as a connecting group, wherein the aniline substituted fluorene is 2-position and 7-position aniline electron-donating groups substituted fluorene.

In some embodiments, the attachment group site of the pyridine group in the backbone structure of the cross-conjugated polymer is a 3,5 site.

In some embodiments, the two aniline electron-donating groups R are located at the 2, 7-position substitution positions on fluorene, and the cross-conjugated polymer has the following general structural formula:

wherein R is aniline electron-donating group, and n is an integer of 10-30.

In some embodiments, the aniline electron donating group is selected from one of diphenylamine, 4' -dimethyldiphenylamine, 4' -dimethoxydiphenylamine, 3' -dimethoxydiphenylamine, phenothiazine, 9, 10-dihydro-9, 9-dimethylacridine, triphenylamine, 4' -dimethyltriphenylamine, 4' -dimethoxytriphenylamine, 2-p-phenyl (4-vinylphenyl) amine, 2-p-tolyl (4-vinylphenyl) amine, 2-p-methoxyphenyl (4-vinylphenyl) amine, and 1-naphthylaminobenzene.

In a preferred embodiment, the aniline electron-donating group is 4,4' -dimethyldiphenylamine, and the cross-conjugated polymer has a general structural formula shown in formula PPY:

wherein n is an integer of 10-30. The compound is synthesized for multiple times in the experimental process, and the obtained polymer n is between 10 and 30.

The invention also provides a preparation method of the cross-conjugated polymer, which is obtained by performing Sonagashira coupling reaction on an aniline substituted fluorene alkene intermediate and 3, 5-diacetylene pyridine. The aniline substituted fluorene alkene intermediate has a structure shown in a formula (I):

in some embodiments, the preparation method specifically comprises:

mixing and dissolving the aniline substituted fluorene intermediate and 3, 5-diacetylene pyridine in an organic solvent, adding a catalyst, organic base and cuprous iodide under the protection of inert atmosphere, heating to reflux, adding methanol for filtration after full reaction, drying the obtained solid, removing the solvent, performing Soxhlet extraction, and drying to obtain the cross conjugated polymer.

For the intermediate shown in the formula (I), when the aniline substituent R in the cross-conjugated polymer is 4,4 '-dimethyldiphenylamine, the intermediate is a 2,7- (4,4' -dimethyl) diphenylamine substituted fluorene intermediate; it has a structure as shown in formula (II):

when R is phenothiazine, the intermediate is 2, 7-diphenothiazine substituted fluorenene correspondingly, and the like. Firstly, synthesizing corresponding disubstituted fluorene intermediate according to different substituent groups, and then preparing the cross-conjugated polymer according to the preparation method.

In some embodiments, the molar ratio of the aniline-substituted fluorene alkene intermediate to 3, 5-diethynylpyridine is 1:1 to 1: 1.1.

In some embodiments, the organic solvent is dry toluene (toluene), the organic base is diisopropylamine, and the catalyst is Pd (PPh)₃)₄。

In some embodiments, the reaction time is 60 to 72 hours.

In some examples, after the reaction is completed and cooled, methanol is added for filtration, and the obtained solid is subjected to soxhlet extraction sequentially using methanol and n-hexane as solvents, and dried to obtain the above-mentioned pyridine-based D-A type cross-conjugated polymer.

The structural formula of the cross-conjugated polymer prepared by the preparation method is shown as PPY.

The cross-conjugated polymer provided by the invention can be used as a hole transport material. Preferably as undoped hole transport material for perovskite solar cells.

Due to the introduction of the electron-withdrawing group pyridine, the HOMO energy level of the material can be effectively reduced, so that the energy level of the material is more matched with perovskite, and the high open-circuit voltage of a device can be obtained. On the other hand, the introduction of pyridine can enhance the push-pull electron effect of molecules, remarkably improve the hole mobility of the material, and solve the problem of low hole mobility of the conventional high-molecular non-doped hole transport material.

The invention belongs to the field of hole transport materials in photoelectric materials, and relates to a cross-conjugated high molecular polymer based on pyridine. The high polymer is a D-A type polymer which takes aniline substituted fluorene as a side chain group and pyridine as a bridging group, the polymer is simple in synthesis process, has appropriate HOMO and LUMO energy levels and higher hole mobility, and the cross conjugated polymer has good film forming property and can be applied to devices in the photoelectric field as a non-doped hole transmission material, and the energy conversion efficiency of the polymer PPY in a trans-structure perovskite solar cell device in the preferred embodiment reaches 22.41%.

The aniline electron-donating groups in the cross-conjugated polymer can be selected from one of diphenylamine, 4' -dimethyldiphenylamine, 4' -dimethoxydiphenylamine, 3' -dimethoxydiphenylamine, phenothiazine, 9, 10-dihydro-9, 9-dimethylacridine, triphenylamine, 4' -dimethyltriphenylamine, 4' -dimethoxytriphenylamine, 2-p-phenyl (4-vinylphenyl) amine, 2-p-tolyl (4-vinylphenyl) amine, 2-p-methoxyphenyl (4-vinylphenyl) amine and 1-naphthylaminobenzene, the substituent groups have similar structures and have certain hole transmission characteristics, and experiments prove that the aniline electron-donating groups are matched with the core structure of the cross-conjugated polymer, it is presumed that the cross-conjugated polymers corresponding to these substituents can be used as a hole transport material, particularly as a hole transport material for a perovskite solar cell, as well as the PPY of the present invention.

The following are specific examples:

example 1

The synthesis route of the compound PPY is shown in figure 1, and specifically comprises the following steps: compound 1(0.73g,1.00mmol), 3, 5-diacetylene pyridine (0.13g,1.00mmol), Pd (PPh)₃)₄(35mg,0.03mmol)，CuI(0.06g,0.30mmol)，iPr₂NH (5mL) and dry toluene (5mL) were added to a 50mL dry Schlenk bottle under N₂Under the condition, three times of freezing, vacuumizing, unfreezing and circulating oxygen removal operations are carried out, and then the reaction is carried out for 72-80h after the temperature is increased to 120 ℃. After cooling, methanol was added and filtered to give a solid. And (3) loading the obtained precipitate into a Soxhlet extractor for extraction, extracting with 50-60mL of methanol and n-hexane for 24-30h respectively, and removing small molecules and a catalyst to obtain 0.12g of a dark yellow solid with the yield of 17.3%.¹H NMR(400MHz,Chloroform-d)δ8.47-8.09(m,ArH),7.69-7.65(m,ArH),7.12-6.89(m,ArH),2.17(br,-CH₃).GPC:M_n＝7.74kDa,PDI＝1.90.

The hydrogen nuclear magnetic spectrum of the compound PPY is shown in FIG. 2. The UV-visible absorption spectrum of the polymeric PPY film measured with a SHIMADZU UV-3600 UV-visible spectrophotometer is shown in FIG. 3.

The PPY polymerization reaction is an uncontrollable polymerization reaction, but the molecular weight can be stabilized at 6000-20000g/mol under the above conditions, namely n in the corresponding structural formula is 10-30, and the repeatability is better.

The Highest Occupied Molecular Orbital (HOMO) level of the polymer PPY was measured by cyclic voltammetry, and the measurement result is shown in fig. 4, and its HOMO level was calculated to be-5.17 eV. The Lowest Unoccupied Molecular Orbital (LUMO) level of the polymer was-2.69 eV as calculated from the optical bandgap obtained by ultraviolet absorption spectroscopy.

Subsequently, the hole mobility of the compound PPY in the undoped case was measured to be 1.90 × 10 by using the Space Charge Limited Current (SCLC) method^-3cm²V^-1s^-1(see FIG. 5), indicating that the compound PPY designed in the present invention has high hole mobility.

The experimental results show that the polymer PPY designed by the invention has proper energy level and high hole mobility, and can be used as a hole transport material to be applied to devices in the photoelectric field.

Example 2

The compound PPY is used as a device of a hole transport material of a perovskite solar cell and has the following performances:

the compound PPY is used as a hole transport material and applied to the preparation of a trans-planar perovskite solar cell without any doping, and the specific device structure is ITO/HTL/perovskite/PCBM/MoO₃Ag, in which the active layer is used (FA)_0.92MA_0.08)_0.9Cs_0.1Pb(I_0.92Br_0.08)₃(FA:NH＝CHNH₃ ⁺；MA:CH₃NH₃ ⁺). The illumination intensity is 100mW cm^-2Under the irradiation condition of simulated sunlight AM1.5G, the J-V curve of a battery device with the compound PPY as the non-doped hole transport material is shown in figure 6, the PCE can reach 22.41 percent at most,20.98% higher than the PTAA of the comparative device. The device efficiency of the unpackaged device under continuous lighting conditions decays as shown in fig. 7, and after 500 hours, the device efficiency using PPY can still be maintained above 97% of the initial efficiency, indicating that PPY has good light stability. Specific device parameters for the PPY and PTAA optimized devices are shown in the table below.

The compound PPY is used as a hole transport material and applied to a trans-planar perovskite solar cell to obtain higher PCE, on one hand, the hole transport capability of the material is ensured by virtue of a diphenylamine substituted fluorene structure of the material, on the other hand, the HOMO energy level of the material is further optimized by introducing a pyridine group, and simultaneously, the hole transport performance of the material is remarkably improved, compared with the hole mobility of a material with a similar structure and a reported benzene ring as a connecting group, the hole transport capability is improved by about 1000 times, the method is the first example that pyridine is used as a main chain structural unit of a non-doped polymer hole transport material, the discovery has strong originality and innovation, and meanwhile, the method has important significance for solving the problem that the current non-doped polymer hole transport material is low in mobility.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.