Single-molecule self-assembled hole transport material, synthesis method and optoelectronic device

Abstract

The present application provides a kind of single molecule self-assembly hole transport material, the material is the carbazole derivative with pyridine dicarboxyl as anchor group, with the chemical general formula shown in the following formula The present application also relates to the synthesis method of the single molecule self-assembly hole transport material and the photoelectric device prepared by using the synthesized material as hole transport material.The single molecule self-assembly hole transport material provided by the present application has good hole transport performance, strong interface passivation ability and is suitable for large-scale preparation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic semiconductors, and particularly relates to a self-assembled hole transport material containing a carbazole derivative, a synthesis method and application in perovskite batteries and perovskite quantum dot light-emitting diodes. BACKGROUND

[0002] An organic semiconductor is a carbon-based material that combines photoelectric properties and a simple manufacturing process, and the energy level, performance, etc. of the material can be adjusted by changing the chemical structure. Organic semiconductors have been successfully used in the manufacture of light-emitting diodes (which are now widely used in mobile phone displays and televisions), solar cells, transistors and sensors. As an important component of new optoelectronic devices, organic hole transport materials are responsible for the collection and transport of holes and the blocking of electrons in the device, and play a crucial role in the photoelectric conversion efficiency and stability of the device.

[0003] In recent years, single-molecule self-assembled (SAM) hole transport materials have become a research hotspot in organic hole transport due to their low raw material price, easy purification, determined molecular structure, use of green alcohol solvents, strong bonding force with ITO substrates and suitable energy levels. The SAM material is firmly anchored to the base surface through the chemical action of the acid (usually phosphoric acid, acetic acid and boric acid, etc.) of the anchoring group with the ITO surface. The other end of the SAM material is usually a hole transport group (usually carbazole or triphenylamine), which plays a role in transporting holes in the device. Therefore, self-assembled hole transport materials play a key role in optoelectronic devices, and the use of organic small molecules containing anchoring groups to prepare hole transport layers has been proven to have excellent charge selection capability (Energy Environ. Sci., 2019, 12, 230-237). However, the organic small molecule hole transport materials with anchoring groups currently developed have poor stability and poor device performance, which affects the application and marketization of self-assembled hole transport materials in optoelectronic devices. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a self-assembled single-molecule (SAM) hole transport material with good hole transport performance, strong interface passivation ability and suitable for large-area preparation.

[0005] In order to achieve the above purpose, the present application provides a single-molecule self-assembled hole transport material, which is a carbazole derivative with pyridine dicarboxyl as an anchoring group, and has a chemical general formula as shown in the following formula I:

[0006]

[0007]

[0008] wherein R1-R2 are independently selected from any one or two of benzofluorene, benzothiophene, benzofuran, indole, and R l R2may be different substitution positions or different substitution numbers; L represents a single bond, phenylene, pyridylene, methylene, ethylene, propylene, butylene, preferably methylene.

[0009] Further, formula I includes, but is not limited to, any one of the following compounds 1 to 16:

[0010]

[0011] The synthesis method of the monomolecular self-assembly hole transport material described in the present application comprises the following steps:

[0012] (a) first, 4-hydroxy pyridine-2, 6-dicarboxylic acid is chlorinated with phosphorus oxychloride, and after the reaction solution is concentrated, it is directly added to a solution of dichloromethane (DCM) mixed with tert-butyl alcohol (TBA) and 4-dimethylaminopyridine (DMAP) to perform esterification reaction, to prepare intermediate 1:

[0013]

[0014] (b) intermediate 1 and pinacol diboron are coupled in a mixed solution of potassium acetate and tetrahydrofuran (THF) by catalytic coupling reaction of tris(dibenzylideneacetone) palladium and 2-dicyclohexylphosphine-2', 4', 6'-triisopropyl biphenyl, to prepare intermediate 2:

[0015]

[0016] (c) intermediate 2 and bromoarene are catalytically coupled in a mixed solution of potassium phosphate and tetrahydrofuran by palladium acetate and X-phos, to prepare intermediate 3:

[0017]

[0018] (d) intermediate 3 is hydrolyzed in a tetrahydrofuran solution of hydrochloric acid to obtain the final product.

[0019]

[0020] Further, in step (a), the molar ratio of 4-hydroxy pyridine-2, 6-dicarboxylic acid, phosphorus oxychloride, tert-butyl alcohol and 4-dimethylaminopyridine is 1:2-3:2-3:0.05-0.1; the esterification reaction temperature is 100-150°C, and the esterification reaction time is 12-24h.

[0021] Further, in step (b), the molar ratio of intermediate 1, bis(pinacolato)diboron, potassium acetate, tris(dibenzylideneacetone) palladium and 2-dicyclohexylphosphino-2',4',6'-triisopropyl biphenyl is 1:1-1.5:1-3:0.02-0.03:0.04-0.06; the coupling reaction temperature is 50-60℃, and the coupling reaction time is 8-12h.

[0022] Further, in step (c), the molar ratio of intermediate 2, bromoarene, potassium phosphate, palladium acetate and 2-dicyclohexylphosphino-2',4',6'-triisopropyl biphenyl is 1:1-1.5:1-3:0.02-0.03:0.04-0.06; the coupling reaction temperature is 50-60℃, and the coupling reaction time is 12-24h.

[0023] Further, in step (d), the pH of the reaction solution is 2-3; the reaction temperature is room temperature, and the reaction time is 3-8h.

[0024] Another object of the present application is the application of the photoelectric device, which at least comprises a transparent conductive glass substrate, a hole transport layer, a light absorption layer, an electron transport layer and an electrode layer; or, comprises a transparent conductive glass substrate, a hole transport layer, a light emission layer, an electron transport layer and an electrode layer in sequence; wherein the hole transport layer is the monomolecular self-assembly hole transport material containing the monomolecular self-assembly hole transport material as shown in the general formula I.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] (1) The monomolecular self-assembly hole transport material provided by the present application has pyridine dicarboxyl as an anchor group in the structure, which can greatly improve the stability of the organic hole transport material, including the chemical stability of the action with the conductive glass, the device thermal stability, the oxidation-reduction stability and the like; on the other hand, it can adjust the work function of the conductive glass, so that it can match the energy level of the active layer material, improve the interface carrier injection or extraction efficiency; and thirdly, it can passivate the structural defects of the interface, prolong the carrier lifetime in the active layer, and improve the open circuit voltage and the filling factor of the photoelectric device.

[0027] (2) The monomolecular self-assembly hole transport material provided by the present application further improves the hole affinity of the molecule by introducing the carbazole derivative in the structure, which is beneficial to the transmission of the carrier, and further improves the hole transport performance of the material. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 This is a schematic diagram of the optoelectronic device structure of the present invention;

[0029] Figure 2 The J / V curve of a perovskite solar cell prepared using compound 1 provided in this invention as a hole transport material is shown.

[0030] Figure 3 The J / V curve of a perovskite solar cell prepared using compound 2 provided in this invention as a hole transport material is shown.

[0031] Figure 4 The J / V curve of a perovskite solar cell prepared using compound 3 provided in this invention as a hole transport material is shown.

[0032] Figure 5 The graph shows the maximum external quantum efficiency (EQE) of a perovskite light-emitting diode prepared using compound 1 provided in this invention as a hole transport material as a function of voltage (V).

[0033] Figure 6 The graph shows the maximum external quantum efficiency (EQE) of a perovskite light-emitting diode prepared using compound 2 provided in this invention as a hole transport material as a function of voltage (V).

[0034] Figure 7 The graph shows the maximum external quantum efficiency (EQE) of a perovskite light-emitting diode prepared using compound 3 provided in this invention as a hole transport material as a function of voltage (V). Detailed Implementation

[0035] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail the specific implementation methods, structures, features and effects of the present invention, taking the chemical formula shown in Formula I, in which L is preferably phenylene, in conjunction with the accompanying drawings and preferred embodiments of the present invention.

[0036]

[0037]

Example 1

[0038] Synthesis of Compound 1

[0039]

[0040] (1) Synthesis of intermediate 1:

[0041]

[0042] Weigh SM1 (48g, 1.0eq) and add it to a 500mL three-necked flask. Add 200mL of POCl3 and connect it to a tail gas treatment device. Absorb the acidic tail gas with an aqueous solution of NaOH. Heat to 100℃ and reflux with stirring for about 10h. Stop the reaction. Rotate off the remaining POCl3. Add tert-butanol (40mL), DMAP (10g), 20mL of ultra-dry DCM, and 10mL of pyridine to a 500mL flask and stir well. Dilute the concentrated solution from the previous step with 50mL of ultra-dry DCM and transfer it to a constant pressure dropping funnel. Slowly add the solution dropwise to the flask. After stirring for about 12h, concentrate the reaction solution and separate by column chromatography. A total of 42.68g of white solid product was obtained, with a yield of 57.6%. 1 H NMR(400MHz,DMSO-d6)δ7.38(s,2H),0.86(s,18H).HRMS(ESI,m / z):[M+H] + Calculated for C 15 H 21 ClNO4,314.1159,found 314.1168.

[0043] (2) Synthesis of intermediate 2:

[0044]

[0045] Weigh intermediate 1 (5.0 g, 1.0 eq), pinacol diborate (4.87 g, 1.2 eq), potassium acetate (4.69 g, 3.0 eq), Pd2(dba)3 (0.15 g), and X-phos (0.30 g) and dissolve them in 50 mL of ultra-dry THF. Stir at 60 °C under argon protection. After stirring for about 10 h, the reaction is complete. Filter the reaction solution, remove salts, and concentrate the reaction solution to about 10 mL. Stir for about 30 min, and a large amount of product precipitates. Filter, wash with petroleum ether, and dry to obtain 6.59 g of white solid product, yield 65.4%. 1 H NMR(400MHz,DMSO-d6)δ7.38(s,2H),0.86(s,30H).HRMS(ESI,m / z):[M+H] + Calculated for C 21 H 32 BNO6,405.2323,found405.2349.

[0046] (3) Synthesis of intermediate 3:

[0047]

[0048] Weigh SM3 (0.30 g, 1 eq), intermediate 2 (0.33 g, 1.2 eq), Pd(OAc)2 (0.05 g), and X-phos (0.10 g), add them to a 50 mL three-necked flask, add THF (20 mL) and water (5 mL), and heat to 50 °C; stir overnight, evaporate to dryness, and separate by column chromatography (PE:EA = 7:1) to obtain a yellow product; dry to obtain 0.36 g, yield 82.7%. 1 H NMR(400MHz,Chloroform-d)δ8.19–8.13(m,3H),7.81(s,1H),7.76–7.70(m,2H),7.62(dd,J=7.4,1.6Hz,1H),7.60–7.51 (m,4H),7.51–7.40(m,3H),7.35(td,J=7.5,1.5Hz,1H),7.29(td,J=7.5,1.5Hz,1H),1.56(s,18H).HRMS(ESI,m / z):[M+H] + Calculated for C 42 H 40 N2O4, 636.7920, found 636.7957.

[0049] (4) Synthesis of Compound 1:

[0050]

[0051] Weigh intermediate 3 (0.30 g, 0.47 mmol), add 20 mL THF and 10 mL water, add concentrated hydrochloric acid dropwise to adjust the pH to 2, stir for 12 h to hydrolyze the ester, and perform TLC. Hydrolysis is complete. When the reaction solution is concentrated to about 10 mL of water, a precipitate forms. After filtration, the product is washed repeatedly with water. After drying, 0.18 g of product is obtained, with a yield of 75.1%. 1 H NMR(400MHz,Chloroform-d)δ8.15(dd,J=7.4,1.5Hz,1H),8.15(s,2H),7.83(s,1H),7.80–7.74(m,2H),7.63(dd,J=7.4,1.6Hz,1H),7.61–7.53( m,4H),7.48(s,1H),7.49–7.40(m,2H),7.35(td,J=7.5,1.6Hz,1H),7.29(td,J=7.5,1.5Hz,1H),1.55(s,6H).HRMS(ESI,m / z):[M+H]+calculated forC 34 H 24N2O4,524.5760, found 524.5718.

[0052]

Example 2

[0053] Synthesis of Compound 2

[0054]

[0055] The synthesis of compound 2 was similar to that of compound 1, yielding 161 mg of product, with a yield of 78.1%. 1 H NMR(400MHz,Chloroform-d)δ8.24(s,1H),8.11(s,1H),8.09–8.03(m,1H),8.06–7.98(m,1H),7.83–7.77(m,2H),7.66–7.57(m,3H ),7.54(dd,J=7.5,1.6Hz,1H),7.47(td,J=7.4,1.5Hz,1H),7.37(td,J=7.4,1.6Hz,1H),7.34–7.24(m,3H).HRMS(ESI,m / z):[M+H] + Calculated for C 31 H 18 N2O5, 498.4940, found 498.4989.

[0056]

Example 3

[0057] Synthesis of compound 3:

[0058]

[0059] The synthesis of compound 3 was similar to that of compound 1, yielding 141 mg of product, with a yield of 73.6%. 1 H NMR(400MHz,Chloroform-d)δ8.37–8.31(m,1H),8.14(s,2H),8.11–8.06(m,1H),7.92(s,1H),7.80–7.73(m,3H),7.69(dd,J= 7.6,1.5Hz,1H),7.66–7.60(m,1H),7.59–7.53(m,2H),7.45(td,J=7.5,1.5Hz,1H),7.37–7.25(m,3H).HRMS(ESI,m / z):[M+H] + Calculated for C 31 H 18 N2O4S,514.5550,found 514.5581.

[0060]

Example 4

[0061] The preparation method of perovskite solar cells is as follows:

[0062] Cleaning of S1 and ITO conductive glass substrates (sonication with pure water, ethanol, and acetone for 30 minutes in sequence);

[0063] S2. Preparation of Hole Transport Layer (HTL): The compound was dissolved in ethanol, tetrahydrofuran or anisole solvent, spin-coated onto ITO, and then annealed at 120°C for 20 min.

[0064] S3. Preparation of perovskite thin film (perovskite layer): The solubility of the perovskite precursor solution was 1.2 M. The perovskite thin film was prepared by a one-step anti-solvent method. Spin coating was performed in two stages, with the first stage at a speed of 1000 rpm. -1 Spin coating for 10 seconds, with an acceleration of 800 rpm. -2 The second stage is 5000 rpm. -1 Apply for 30 seconds, with an acceleration of 2000 rpm. -2 20 seconds before the end of the second stage, 400 μL of ethyl acetate was added dropwise to the center of the perovskite film as an antisolvent, and finally heated at 100°C for 30 min to obtain the final perovskite film.

[0065] S4. Preparation of the electron transport layer (ETL) and hole blocking layer: A solution of PCBM was prepared using chlorobenzene at a concentration of 20 mg / mL. -1 Two-step spin coating process (800 rpm) -1 10s; 4000 rpm -1 Anneal at 80℃ for 10 minutes (30s).

[0066] S5. Hole blocking layer preparation: Finally, a hole blocking layer (ITO) is prepared by drop-coating 120 μL of isopropanol solution.

[0067] S6. Back electrode preparation: using a vacuum evaporation apparatus (<5×10⁻⁶). -4 The negative electrode is formed by evaporating 100nm of silver (Pa).

[0068] Perovskite solar cell performance testing: The current-voltage characteristic curve (IV) of the solar cell was recorded using a Keithley 2400 digital source meter, with a xenon lamp (Osram XBO 450) simulating AM 1.5 sunlight at an intensity of 1000 W / m². 2After calibration with silicon cells, the test temperature was 25℃. The incident photon-to-electron coverage efficiency (IPCE), also known as external quantum efficiency (EQE), was measured using an Oriel-74125 system with a 300W xenon lamp (ILC Technology, USA) as the light source and a modulation frequency of 2Hz. The JV data of the tested cells are shown in Table 1 and... Figures 2-4 .

[0069] Stability test of perovskite solar cells: After the prepared perovskite solar cell device was placed under conditions of 85% relative humidity (RH) and 50℃ for 240h, the relative values ​​of its photoelectric conversion efficiency compared with the original efficiency are shown in Table 1.

[0070] Table 1

[0071]

[0072] From Table 1 and Figures 2-4 It can be seen that: (1) When the pyridine carboxyl compound of the present invention is used as a hole transport material in a perovskite solar cell, the short-circuit density of the cell is greater than 20 mA / cm². -2 The open-circuit voltage is greater than 1.00V and the filler is greater than 70%. Compared with the 2PACz compound, it shows excellent light conversion efficiency. This is mainly due to the introduction of carbazole unit and pyridine dicarboxyl group, which adjusts the energy level of the material to better match the energy level of the active layer material, improves the interface carrier injection and extraction efficiency, and improves the device efficiency. In addition, by passivating the structural defects of the interface, the carrier lifetime in the perovskite active layer is extended, and the open-circuit voltage and filler factor of the perovskite battery are improved. (2) Due to the introduction of carbazole unit and pyridine carboxyl group, the chemical adsorption stability of hole transport material can be improved. As can be seen from Table 1, after being placed under high temperature and high humidity for 240 hours, the perovskite battery using the compound of the present invention as the hole transport material still has good photoelectric conversion efficiency. Compared with the original value, it is higher than 80%, while the reference device is only 45%, showing the good stability of the battery of the present invention.

[0073]

Example 5

[0074] The fabrication method of perovskite light-emitting diode devices is as follows:

[0075] S1, ITO anode: The ITO (indium tin oxide) glass substrate with a coating thickness of 150nm was wiped with ethanol, then cleaned twice with acetone, ultrasonically cleaned for 20min, and then transferred to an isothermal stage for drying. After baking, it was cooled and transferred to UV-O3 treatment for 15min.

[0076] S2. Preparation of Hole Transport Layer (HTL): The compound was dissolved in ethanol, tetrahydrofuran or anisole solvent, spin-coated onto ITO, and then annealed at 120°C for 20 min.

[0077] S3. Spin-coating perovskite quantum dots onto the transport layer at 2000 rpm / 45 s with an acceleration of 1000. Then, using a vacuum evaporation apparatus, deposit 45 nm of TPBi as the electron transport layer. On the electron injection layer, vacuum evaporate 100 nm of Al as the back electrode.

[0078] The prepared perovskite light-emitting device was subjected to IVL testing, and its relevant performance parameters are shown in Table 2.

[0079] Table 2

[0080]

[0081] From Table 2 and Figures 5-7 It can be seen that: (1) When the pyridine carboxyl compound of the present invention is used as a hole transport material in a perovskite light-emitting diode, the turn-on voltage is 2.6V and the luminous intensity is greater than 10000cd / m². 2 The external quantum efficiencies of all compounds are greater than 14%. The introduction of transport units and pyridine carboxyl groups modulates the frontier orbital energy levels of the materials, making them more compatible with the energy levels of the active layer material, resulting in excellent interfacial carrier injection and extraction efficiency. These tests demonstrate that compounds 1-3 have broad application potential in perovskite light-emitting diodes.

Claims

1. A single-molecule self-assembled hole transport material having the following general chemical formula (I): （I） Its features are, Formula (I) is any one of the following compounds 1 to 3 and compounds 5 to 7:

2. A method for synthesizing the single-molecule self-assembled hole transport material according to claim 1, comprising the following steps: (a) The step of preparing intermediate 1 by chlorinating 4-hydroxypyridine-2,6-dicarboxylic acid with phosphorus oxychloride, concentrating the reaction solution, and then directly adding it dropwise to a solution of dichloromethane mixed with tert-butanol and 4-dimethylaminopyridine: ； (b) The step of preparing intermediate 2 by catalytic coupling reaction of intermediate 1 and pinacol diborate in a mixed solution of potassium acetate and tetrahydrofuran via tris(dibenzylacetone)palladium and 2-dicyclohexylphosphine-2′,4′,6′-triisopropylbiphenyl: (c) The step of preparing intermediate 3 by catalytic coupling reaction of intermediate 2 and bromoaromatic hydrocarbon in a mixed solution of potassium phosphate and tetrahydrofuran via palladium acetate and X-phos: ； (d) Intermediate 3 was hydrolyzed in a tetrahydrofuran solution of hydrochloric acid to give the final product; ； In the above reaction formula, the definitions of R1-R2 in the final product structure are the same as the corresponding groups in the structures of compounds 1 to 3 and compounds 5 to 7 in claim 1.

3. The method for synthesizing a single-molecule self-assembled hole transport material as described in claim 2, characterized in that, In step (a), the molar ratio of 4-hydroxypyridine-2,6-dicarboxylic acid, phosphorus oxychloride, tert-butanol and 4-dimethylaminopyridine is 1:2~3:2~3:0.05~0.1; the esterification reaction temperature is 100~150℃ and the esterification reaction time is 12~24h.

4. The method for synthesizing a single-molecule self-assembled hole transport material as described in claim 2, characterized in that, In step (b), the molar ratio of intermediate 1, pinacol diboronate, potassium acetate, tris(dibenzylacetone)palladium, and 2-dicyclohexylphosphine-2′,4′,6′-triisopropylbiphenyl is 1:1~1.5:1~3:0.02~0.03:0.04~0.06; the coupling reaction temperature is 50~60℃, and the coupling reaction time is 8~12h.

5. The method for synthesizing a single-molecule self-assembled hole transport material as described in claim 2, characterized in that, In step (c), the molar ratio of intermediate 2, bromoaromatic hydrocarbon, potassium phosphate, palladium acetate, and 2-dicyclohexylphospho-2′,4′,6′-triisopropylbiphenyl is 1:1~1.5:1~3:0.02~0.03:0.04~0.06; the coupling reaction temperature is 50~60℃, and the coupling reaction time is 12~24h.

6. The method for synthesizing a single-molecule self-assembled hole transport material as described in claim 2, characterized in that, In step (d), the pH of the reaction solution is 2-3; the reaction temperature is room temperature; and the reaction time is 3-8 hours.

7. An optoelectronic device, comprising a transparent conductive glass substrate, a hole transport layer, a light absorption layer, an electron transport layer, and an electrode layer sequentially disposed thereon; or comprising a transparent conductive glass substrate, a hole transport layer, a light-emitting layer, an electron transport layer, and an electrode layer sequentially disposed thereon; characterized in that, The hole transport layer is obtained by dissolving any one of the monomolecular self-assembled hole transport materials containing the compound 1 to 3 and compound 5 to 7 of general formula (I) as described in any one of claims 1 in solvents such as alcohols, tetrahydrofuran, and anisole, and then coating the solution with a concentration of 1 to 10 mg / mL onto a transparent conductive glass substrate.

8. The optoelectronic device as described in claim 7, characterized in that, The aforementioned optoelectronic device is a perovskite solar cell or a perovskite quantum dot light-emitting diode.

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