CN109836369B - A spiroindene-like hole-transporting small molecule and its application in perovskite solar cells - Google Patents

Abstract

The invention provides a hole-transporting small molecule material containing a spiroindene structure. It uses a spiro indene structure as the core, which not only has spiro atom connections similar to the classical material Spiro‑OMeTAD, but also has better solubility; the introduction of carbazole triphenylamine dendrimer units can ensure better HOMO energy levels and holes mobility. Used as a hole transport layer in perovskite solar cells, the photoelectric conversion efficiency can reach up to 18.55%.

Description

A spiroindene-like hole-transporting small molecule and its application in perovskite solar cells

technical field

The invention relates to the field of perovskite solar cells, in particular to a method for preparing a class of hole-transporting small molecules containing a spiroindene structure and its application in perovskite solar cell devices.

Background technique

In recent years, the "energy crisis" and the environmental problems caused by the burning of fossil energy have attracted more and more attention, and it is imperative to develop renewable and environmentally friendly new energy. Among them, solar energy is very important to the sustainable development of human society because it is "inexhaustible and inexhaustible" and the cleanest. The development of new low-cost, high-efficiency solar cells has become a research hotspot in recent years. Among them, perovskite solar cells have developed rapidly, and the device efficiency has rapidly increased from 3.8% in 2009 ^[1] to 22.1% in 2016 ^[2] . It has attracted worldwide attention and has become one of the research hotspots in the field of new solar cells. .

Perovskite materials such as CH ₃ NH ₃ PbI ₃ (MAPbI ₃ ) have many advantages, such as high extinction coefficient and suitable band gap ^[3] , low exciton binding energy ^[4] , long charge diffusion distance ^[5] , Due to the high mobility of electrons ^[6] and wide spectral absorption range ^[7] , it is very suitable as a light-absorbing material for solar cells. The main reasons for the rapid increase in the efficiency of such battery devices are the optimization of perovskite material components and preparation methods ^[8] and the development of novel high-efficiency charge collection materials ^[9] . Charge collection materials, including electron transport materials and hole transport materials (HTMs), are an essential part of driving perovskite solar cell devices to achieve higher efficiency and higher stability ^[10] .

Spiro-OMeTAD, a small molecule of spirofluorene, as a hole transport layer material, combined with the excellent preparation method of perovskite, has achieved a device efficiency of more than 20%, and is currently the most widely used classical hole transport material ^[11] . However, 2,2',7,7'-tetrabromo-9,9'-spirofluorene is used as the raw material for the synthesis of Spiro-OMeTAD, and the synthesis process of this raw material needs to be kept at a low temperature of -78°C, as well as temperature and humidity. All sensitive chemical reagents (n-butyllithium or Grignard reagent) and liquid bromine (very toxic and corrosive and volatile) are used. In addition, the synthesized Spiro-OMeTAD needs to undergo a sublimation process to further improve the purity to obtain higher device performance. These problems increase the synthetic cost of Spiro-OMeTAD ^[12] , limiting its large-scale application. Therefore, it is of great significance to develop novel hole transport materials with high efficiency and low cost.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a hole-transporting small molecule material containing a spiroindene structure. The hole transport material of the present invention has a spiro-indene structure as the core, which not only has spiro atom connections similar to the classical material Spiro-OMeTAD, but also has better solubility; the introduction of carbazole triphenylamine dendritic units can ensure better The HOMO energy level and hole mobility are combined to ensure that the material has excellent device performance.

In order to achieve the above object, the technical scheme of the present invention is as follows:

A kind of small molecule containing spiroindene structure, it is characterized in that, its chemical structural formula general formula is as follows:

The symbols and coefficients in the general formula have the following meanings:

R ₁ is H, -OH, C ₁ -C ₃ -alkoxy or C ₁ -C ₃ -alkyl;

a, b are the same or different and are 0, 1 or 2;

G ₁ and G ₂ are the same or different, and are represented by the following structural formula:

The symbols and coefficients in the formula have the following meanings:

c is the same or different and is 0, 1 or 2;

Ar ₁ , Ar ₂ , and Ar ₃ are the same or different, and are the following structural units

R ₂ in the formula is H, C ₁ -C ₁₀ -alkyl or C ₁ -C ₁₀ -alkoxy;

Ar ₁ ', Ar ₂ ', Ar ₃ ', Ar ₄ ' are the same or different, and are the following structural units

R ₃ in the formula is H, C ₁ -C ₄ -alkyl.

The second object of the present invention is to provide the application of the above hole transport material containing spiroindene structure. The hole transport material of the present invention is used in the application field of perovskite solar cells, so that it has higher photoelectric conversion efficiency and better repeatability. Taking the material compound A in Example 1 as an example, using it as a hole transport layer, the prepared device is tested for photoelectric conversion efficiency, and its conversion rate can reach up to 18.55%.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: the application of the above-mentioned hole transport material containing a spiro-indene structure in a perovskite solar cell device.

the term:

"NBS" refers to N-bromosuccinimide, N-bromosuccinimide.

"DMF" means N,N-Dimethylformamide, N,N-Dimethylformamide.

"Pd ₂ dba ₃ " refers to tris(dibenzylideneacetone)dipalladium.

"Pd(dppf)Cl2" refers to 1,1' _- bis(diphenylphosphino)ferrocene palladium(II) chloride.

"S-phos" refers to 2-dicyclohexylphosphine-2',6'-dimethoxybiphenyl.

The beneficial effects of the present invention are:

1. The hole transport material of the present invention uses a spiro indene structure to replace the classical 9,9'-spirobifluorene, which on the one hand retains the spiro atom connection in the classical material Spiro-OMeTAD, and on the other hand increases its own solubility, In addition, it is easy to synthesize and purify, and has lower synthetic cost; the introduced carbazole-like dendritic unit is used to adjust the energy level, and this kind of unit is introduced into the molecule in the form of a branch, which can make the molecule have a three-dimensional structure and avoid material crystallization; At the same time, the thermal stability of the material can be greatly improved, thereby improving the battery efficiency; in addition, the dendritic three-dimensional structure can also increase the solubility of the material, improve the film-forming performance of the material, and reduce the requirements for device preparation.

2. The preparation method of the hole transport material of the present invention has a simple synthesis route, mild reaction conditions, and all the reactions involved are normal pressure reactions; The raw materials are readily available and all are commercially available.

3. The hole transport material of the present invention is used in the application field of perovskite solar cells, so that it has high photoelectric conversion efficiency. Taking the material compound A as an example, the photoelectric conversion efficiency of the prepared device was tested by using it as the hole transport layer, and the conversion rate was up to 18.55%.

4. The preparation method of the perovskite solar cell device of the present invention has simple and easy operation steps, and the required raw materials and equipment are easy to purchase.

5. The spiroindene-based small molecules obtained in the present invention have better film-forming properties, and when used as a hole transport layer of a perovskite solar cell device, the amount of material used is less. Taking the material compound A as an example, under the optimal conditions of the same device, its dosage is only 1/4 of that of the classical material Spiro-OMeTAD. Therefore, this shows that the compound obtained by the present invention is a kind of hole transport material with excellent performance.

Description of drawings

FIG. 1 is a structural diagram of a perovskite solar cell device made of the hole transport material of the present invention.

In the accompanying drawings, the list of components represented by each number is as follows:

1. Glass substrate, 2. FTO cathode, 3. Dense _TiO2 layer, 4. Perovskite layer, 5. Hole transport layer, 6. Au electrode.

FIG. 2 is the current-voltage curve of the perovskite solar cell device made with Example 1 as the hole transport material.

3 is the ultraviolet absorption spectrum of the tetrahydrofuran solution of Example 1 and Example 2.

4 is the cyclic voltammetry curves of the dichloromethane solutions of Example 1 and Example 2.

Detailed ways

The following examples illustrate the invention in more detail without limiting the invention to these examples.

The synthesis of the required intermediate compounds in the synthetic examples is as follows:

Synthesis of compound 2:

Under argon protection, 4.6 g (15 mmol) of compound 1, 8.3 g (30 mmol) of potassium carbonate and 50 mL of DMF were mixed and stirred at room temperature, and then 2.4 mL (19.5 mmol) of iodomethane was added dropwise. After stirring at room temperature for 12 h, the reaction solution was poured into 2500 mL of water, and 5 g of white product was obtained by suction filtration (yield 99%). LC-MS: _C23H28O2 , _calcd : _336.21 , found: [M] ⁺ =336.21. ¹ H NMR(400MHz, DMSO)δ7.14(d,J=8.3Hz,2H),6.79(dd,J=8.3,2.3Hz,2H),6.19(d,J=2.3Hz,2H),3.63( s, 6H), 2.23 (d, J=35.9Hz, 4H), 1.31 (d, J=29.1Hz, 12H). The synthetic route is as follows:

Synthesis of compound 3:

10 g (30 mmol) of compound 2 were dissolved in 100 mL of DMF. DMF solution containing 12 g of NBS (84 mmol) was added dropwise to the reaction in an ice-water bath, and after the dropping was completed, the solution was returned to room temperature and stirred for 12 h. After the reaction, the reaction solution was poured into 2000 mL of water, and 14 g of white product was obtained by suction filtration (yield 99%). LC _- MS: _C23H28Br2O2 , _calcd : _492.03 , found: [M] ⁺ =492.03. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.33 (s, 2H), 6.29 (s, 2H), 3.74 (s, 6H), 2.27 (d, J=47.0 Hz, 4H), 1.35 (d, J= 20.5Hz, 12H). The synthetic route is as follows:

Synthesis of compound 5:

Under argon, 1.24 g (2.5 mmol) of compound 3, 2.12 g (5.75 mmol) of compound 4, 0.032 g (0.035 mmol) of Pd ₂ (dba) ₃ , 0.057 g (0.14 mmol) of phosphine ligand S-phos and 30mL of toluene was mixed and stirred. After the temperature was raised to 90 °C, 10 mL of potassium carbonate aqueous solution (2 M) was added, and the reaction was stirred for 12 h. After the reaction, toluene was evaporated to dryness, and dichloromethane and water were added. After extraction, liquid separation, drying over anhydrous sodium sulfate, and silica gel column passing, 1.02 g of white solid was obtained (yield 50%). LC-MS: _C59H50N2O2 , _calcd : _818.39 , found: [M] ₊ ⁼ 818.39. ¹ H NMR (400 MHz, CDCl ₃ ) δ 8.17 (d, J=7.7 Hz, 4H), 7.83 (d, J=8.4 Hz, 4H), 7.63 (d, J=8.4 Hz, 4H), 7.54 (d , J=8.2Hz, 4H), 7.46–7.40 (m, 4H), 7.33–7.26 (m, 6H), 6.57 (s, 2H), 3.79 (s, 6H), 2.43 (dt, J=24.2, 12.2 Hz, 4H), 1.45 (dd, J=24.9, 15.5Hz, 12H). The synthetic route is as follows:

Synthesis of compound 6:

3.38 g (4.13 mmol) of compound 5 were dissolved in 100 mL of dichloromethane. Under an ice-water bath, 3.09 g (17.346 mmol) of NBS was added to the reaction solution in batches, and after the addition was completed, the room temperature was naturally returned to, and stirring was continued for 10 h. After the reaction, the reaction solution was washed with water, dried over anhydrous sodium sulfate, and evaporated to dryness to obtain 4.60 g of a white solid (yield 95%). LC _- MS: _{C59H50Br4N2O2} , _calcd : _1130.03 , found: [M] ₊ ⁼ 1130.03. ¹ H NMR (400 MHz, CDCl ₃ ) δ 8.22 (d, J=1.8 Hz, 4H), 7.83 (d, J=8.4 Hz, 4H), 7.57-7.50 (m, 8H), 7.39 (d, J= 8.7Hz, 4H), 7.25(s, 2H), 6.56(s, 2H), 3.79(s, 6H), 2.44(dd, J=38.0, 13.0Hz, 4H), 1.48(d, J=23.4Hz, 12H). The synthetic route is as follows:

Example 1

The synthesis of compound A was achieved by two schemes:

Under argon, 1.14 g (1 mmol) of compound 6, 1.1 g (4.8 mmol) of 4,4'-dimethoxydiphenylamine, 0.036 g (0.039 mmol) of Pd ₂ (dba) ₃ , 0.032 g (0.158 g of mmol) tri-tert-butylphosphine, 0.77 g (8 mmol) of sodium tert-butoxide and 20 mL of toluene were mixed and stirred, and the temperature was raised to 110° C. to react for 12 h. After the reaction, toluene was evaporated to dryness, ethyl acetate and water were added, and after extraction, liquid separation, and drying over anhydrous sodium sulfate, neutral alumina was used, and a mixed solvent of n-hexane and ethyl acetate was used as the eluent. 1.00 g of yellow solid (yield 58%). LC-MS: _{C115H102N6O10} , _calcd : _1726.77 , found: [M] ⁺ = _1726.77 . ¹ H NMR(400MHz, DMSO)δ7.78(d,J=8.3Hz,4H),7.73(d,J=1.6Hz,4H),7.63(d,J=8.4Hz,4H),7.36(d, J＝8.8Hz, 4H), 7.30(s, 2H), 7.11(dd, J＝8.9, 1.6Hz, 4H), 6.88(d, J＝9.0Hz, 16H), 6.82(d, J＝9.0Hz, 16H), 6.55(s, 2H), 3.70(s, 30H), 2.36(dd, J=32.4, 12.8Hz, 4H), 1.43(d, J=32.9Hz, 12H). Its UV light in tetrahydrofuran solution The absorption and cyclic voltammetry curves in the dichloromethane solution are shown in Figure 3 and Figure 4, and the specific synthetic route is as follows:

Synthesis of Example 2 Compound B:

Under argon, 1.14 g (1 mmol) of compound 6, 0.965 g (4.4 mmol) of N-phenyl-1-naphthylamine, 0.036 g (0.039 mmol) of Pd ₂ (dba) ₃ , 0.032 g (0.158 mmol) of Tri-tert-butylphosphine, 0.77 g (8 mmol) of sodium tert-butoxide and 20 mL of toluene were mixed and stirred, and the temperature was raised to 110° C. to react for 12 h. After the reaction, toluene was evaporated to dryness, dichloromethane and water were added, and after extraction, liquid separation, and drying over anhydrous sodium sulfate, neutral alumina was used, and a mixed solvent of n-hexane and ethyl acetate was used as the eluent, and the column was separated. 0.98 g of yellow solid was obtained (yield 58%). LC-MS: _C123H94N6O2 , _calcd : _1686.74 , found: [M] ⁺ = _1686.74 . ¹ H NMR (400MHz, DMSO) δ8.18(s, 4H), 7.94-7.78(m, 14H), 7.69(d, J=7.8Hz, 4H), 7.55(t, J=9.7Hz, 8H), 7.46–7.29(m, 26H), 7.13(d, J=8.0Hz, 6H), 7.06(t, J=7.3Hz, 4H), 7.00(d, J=8.9Hz, 4H), 6.65(s, 2H ), 3.83(s, 6H), 2.45(d, J=19.9Hz, 4H), 1.59–1.45(m, 12H). Its UV absorption in tetrahydrofuran solution and its cyclic voltammetry in dichloromethane solution are as follows As shown in Figure 3 and Figure 4, the specific synthetic route is as follows:

Example 3

Application of hole transport materials containing spiroindene structures in perovskite solar cell devices.

A perovskite solar cell device, as shown in Figure 1, each layer is a glass substrate 1, a FTO cathode 2, a dense _TiO2 layer 3, a perovskite layer 4, a hole transport layer 5 and an Au electrode 6 in order. The hole transport layer 5 is prepared from the spiro ring hole transporting small molecule material (eg compound A) as described above.

The preparation process of the perovskite solar cell device:

(1) Cleaning: ultrasonically clean the FTO glass substrate with isopropanol, ethanol, and secondary water successively to remove contaminants on the surface of the substrate, and blow dry the cleaned FTO glass substrate with nitrogen. Treat with UV-ozone for 20min before use to further remove organic matter on the surface;

(2) Preparation of dense TiO ₂ layer: A 0.2 mol/L titanium tetrachloride aqueous solution was prepared, and a clean FTO glass substrate was immersed in the solution, and reacted in an oven at 70 °C for 1 h. After the reaction, the FTO glass substrate deposited with dense TiO ₂ was taken out, washed with secondary water, and finally blown dry with nitrogen to keep the surface clean and clean;

(3) Preparation of perovskite active layer: The FTO glass substrate on which dense _TiO was deposited was transferred to a glove box, and a perovskite precursor solution with a concentration of 1 mol/L was spin-coated (mixed solvent, whose components were DMF, The volume ratio of DMSO is 4:1) to prepare a 300 nm thick perovskite active layer, the composition structure is [CH(NH ₂ ) ₂ PbI ₃ ] _0.85 (CH ₃ NH ₃ PbBr) _0.15 , and annealed at 150 °C after spin coating 10min.

(4) Preparation of hole transport layer: After the perovskite layer was cooled, spin-coat the chlorobenzene solution of the spiroindene-based small molecule material Compound A (concentration: 20 mg/mL), add 7.3 μL 4-tert-butylpyridine, 4.4 μL Lithium salt solution (520 mg Li-TFSI in 1 mL acetonitrile).

(5) Preparation of Au anode: The substrate after spin-coated hole transport layer was placed in a vacuum evaporation chamber, and metal Au with a thickness of about 120 nm was vacuum evaporated to complete the preparation of perovskite solar cell devices.

Taking compound A prepared in Example 1 as the hole transport layer of the above solar cell device (perovskite solar cell) as an example, the structure of the perovskite solar cell device is: FTO glass substrate/dense TiO ₂ layer/[ _CH ( _NH2 ) _2PbI3 ] _0.85 ( _CH3NH3PbBr ) _0.15 ( _perovskite ) layer/hole transport layer/Au electrode. The IV test of the above completed perovskite solar cell was performed. As shown in Figure 2, the short-circuit current of the device was 24.68mA/cm ² , the fill factor was 70.9%, the open-circuit voltage was 1.06V, and the energy conversion efficiency was 18.55%.

references:

[1] Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T.J.Am.Chem.Soc., 2009,131,6050–6051.

[2] NREL, Best Research-Cell Efficiencies, http://www.nrel.gov, accessed: November 2016.

[3] Eperon, G.E.; Stranks, S.D.; Menelaou, C.; Johnston, M.B.; Herz, L.M.;

[4] Stranks, S.D.; Eperon, G.E.; Grancini, G.; Menelaou, C.; Alcocer, M.J.P.; Leijtens, T.; Herz, L.M.; Petrozza, A.;

[5] Dong, Q.F.; Fang, Y.J.; Shao, Y.C.; Mulligan, P.; Qiu, J.; Cao, L.; Huang, J.S. Science 2015, 347, 967.

[6] Motta, C.; El-Mellouhi, F.; Sanvito, S. Sci. Rep. 2015, 5, 12746.

P.；Niesen,B.；Ledinsky,M.；Haug,F.J.；Yum,J.H.；Ballif,C.J.Phys.Chem.Lett.2014,5,1035.[7] DeWolf, S.; Holovsky, J.; Moon, SJ;

P.; Niesen, B.; Ledinsky, M.; Haug, FJ; Yum, JH; Ballif, CJPhys.Chem.Lett.2014,5,1035.

[8] Song, T.B.; Chen, Q.; Zhou, H.; Jiang, C.; Wang, H.H.; Yang, Y.; Liu, Y.; You, J.; Yang, Y.J.Mater.Chem.A 2015 ,3,9032.

[9] Zhang, Y.; Liu, M.; Eperon, G.E.; Leijtens, T.C.; McMeekin, D.; Saliba, M.; Zhang, W.; de Bastiani, M.; Petrozza, A.; Herz, L.M. ; Johnston, M.B.; Lin, H.; Snaith, H.J. Mater. Horiz. 2015, 2, 315.

M.；Han,L.Science 2015,350,944.[10] Chen, W.; Wu, Y.; Yue, Y.; Liu, J.; Zhang, W.; Yang, X.; Chen, H.; Bi, E.; Ashraful, I.;

M.; Han, L. Science 2015, 350, 944.

[11] Yang, W.S.; Noh, J.H.; Jeon, N.J.; Kim, Y.C.; Ryu, S.; Seo J.; Seok, S.I. Science, 2015, 348, 1234–1237.

[12] Malinauskas, T.; Saliba, M.; Matsui, T.; Daskeviciene, M.; Urnikaite, S.; Gratia, P.; Send, R.; Wonneberger, H.; Bruder, I.; Graetzel, M.; Getautis, V.; Nazeeruddin, M.K., Energy.Environ.Sci.2016, 9, 1681-1686.

[13] Ma, X.; Swaidan, R.; Belmabkhout, Y.; Zhu, Y.; Litwiller, E.; Jouiad, M.; Pinnau, I.; Han, Y., Macromolecules 2012, 45, 3841- 3849.

[14] Lv, H.-j.; Ma, R.-f.; Zhang, X.-t.; Li, M.-h.; Wang, Y.-t.; Wang, S.; Xing, G.-w., Tetrahedron 2016, 72, 5495-5501.

[15] You, J.; Li, G.; Wang, Z., Polymer 2012, 53, 5116-5123.

[16] Xu, B.; Sheibani, E.; Liu, P.; Zhang, J.; Tian, H.; Vlachopoulos, N.; Boschloo, G.; Kloo, L.; Hagfeldt, A.; Sun, L., Advanced Materials 2014, 26, 6629-6634.

[17] Meng Hong Hu Zhao Huang Wei. An organic hole transport material for all-solid-state perovskite sensitized solar cells [P]. Chinese Patent: CN 104230773 A, 2014-12-24.

[18] Hanthorn, J.J.; Valgimigli, L.; Pratt, D.A., J.Org.Chem. 2012, 77, 6908-6916.

[19] Zhu, L.; Shan, Y.; Wang, R.; Liu, D.; Zhong, C.; Song, Q.; Wu, F., Chem. Eur. J. 2017, 23, 1- 8.

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (3)

1. A small molecule containing a spiroindene structure is characterized in that the chemical structural formula (I) is as follows:

or

The chemical structural formula (II) is as follows:

。

2. use of a small molecule comprising a spiroindene structure of claim 1 in a perovskite solar cell.

3. The perovskite solar cell as claimed in claim 2, which consists of a glass substrate layer, an FTO cathode layer, a dense TiO layer laminated in this order₂The hole transport layer is prepared by taking the spiro hole transport micromolecule material as a hole transport material.

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