A fluorene-based organic small molecule hole transport material and its application

Abstract

This invention discloses a fluorene-based organic small molecule hole transport material and its applications. The general structural formula of the fluorene-based organic small molecule hole transport material is as follows: where n = 1-4, and R represents the hole transport capacity. This fluorene-based organic small molecule hole transport material is used as an undoped hole transport material in perovskite solar cell devices. By introducing dicarboxylic acid groups onto the fluorene-based organic small molecule hole transport material, when used in an inverted perovskite solar cell device, it can form chemical bonds with the hydroxyl groups of the glass conductive substrate, forming a directionally aligned self-assembled layer on the surface of the glass conductive substrate. This effectively improves the charge transport capability at the interface and increases the photoelectric conversion efficiency of the perovskite solar cell device. Furthermore, since this perovskite solar cell device does not contain lithium salts, it exhibits high water and oxygen stability. In addition, the synthesis process of this fluorene-based organic small molecule hole transport material is simple, and the raw materials are inexpensive and readily available, making it highly valuable for practical applications.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials technology, specifically to a fluorene-based organic small molecule hole transport material and its applications. Background Technology

[0002] Perovskite solar cell devices have made remarkable progress due to their excellent photoelectric performance. Since 2009, their photoelectric conversion efficiency (PCE) has exceeded 26%, which is very close to that of crystalline silicon-based solar cells, and they have great development potential.

[0003] Perovskite solar cell devices mainly consist of transparent conductive glass, an electron transport layer, a perovskite active layer, a hole transport layer, and conductive electrodes (metals or conductive metal oxides). Solar cell device structures can be divided into upright structures (nip) and inverted structures (pin). Pin-type devices have advantages such as better stability, lower hysteresis, low-temperature fabrication capability, and suitability for flexible substrates, making them promising for commercial applications. The hole transport layer is a crucial component of perovskite solar cell devices. Besides enabling hole extraction and transport, it also passivates perovskite layer defects and protects the perovskite layer from damage caused by external moisture and oxygen. Hole transport materials can be categorized into inorganic materials (NiO, CuI, CuSCN, etc.), organic polymer materials (PTAA, PEDOT:PSS, P3HT, etc.), and small organic molecules (Spiro-OMeTAD, 2PACz, etc.). Compared to inorganic hole transport materials, the most significant advantage of organic hole transport materials is that energy levels can be tuned and molecularly energized through molecular design modification. The mainstream hole transport materials used in inverted solar cells are polymers PTAA and PEDOT:PSS. However, these materials suffer from drawbacks such as high cost, the need for dopants to improve hole mobility, and inherent corrosiveness and hygroscopicity, which can damage the perovskite layer and affect cell stability, thus limiting their large-scale application. Furthermore, the transparent conductive glass used in perovskite solar cell fabrication requires high-temperature annealing after sputtering deposition, resulting in high surface roughness and difficulty in controlling surface composition and work function, which is detrimental to charge transport at the interface. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a fluorene-based organic small molecule hole transport material and its application.

[0005] The technical solution of the present invention is as follows:

[0006] A fluorene-based organic small molecule hole transport material has the following general structural formula:

[0007]

[0008] Where n = 1 - 4, R is or

[0009] In a preferred embodiment, the structural formula of the fluorene-based organic small molecule hole transport material is as follows:

[0010]

[0011] A method for preparing the above-mentioned fluorene-based organic small molecule hole transport material, wherein the reaction formula is as follows:

[0012]

[0013] Application of the above-mentioned fluorene-based organic small molecule hole transport material as a hole transport material in the fabrication of perovskite solar cell devices.

[0014] The beneficial effects of this invention are:

[0015] This fluorene-based organic small molecule hole transport material is used as an undoped hole transport material in perovskite solar cell devices. By introducing dicarboxylic acid groups onto the fluorene-based organic small molecule hole transport material, when used in inverted perovskite solar cell devices, it can form chemical bonds with the hydroxyl groups of the glass conductive substrate, forming a directionally aligned self-assembled layer on the surface of the glass conductive substrate. This effectively improves the charge transport capability at the interface and enhances the photoelectric conversion efficiency of the perovskite solar cell device. Furthermore, since this perovskite solar cell device does not contain lithium salts, it exhibits high water and oxygen stability. In addition, the synthesis process of this fluorene-based organic small molecule hole transport material is simple, and the raw materials are inexpensive and readily available, making it highly valuable for practical applications. Attached Figure Description

[0016] Figure 1 The 1H NMR spectrum of the fluorene-based organic small molecule hole transport material in the examples;

[0017] Figure 2 The carbon NMR spectrum of the fluorene-based organic small molecule hole transport material in the examples;

[0018] Figure 3 The UV-Vis absorption spectrum of the fluorene-based organic small molecule hole transport material in the examples is shown.

[0019] Figure 4 The cyclic voltammetry curves of the fluorene-based organic small molecule hole transport material in the examples are shown.

[0020] Figure 5 The JV curves are for perovskite solar cell devices based on the aforementioned fluorene-based organic small molecule hole transport materials. Detailed Implementation

[0021] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0022] Unless otherwise specified, the detection methods in the following embodiments are conventional detection methods; and the reagents in the following embodiments are commercially available unless otherwise specified.

[0023] Example 1

[0024] A method for preparing fluorene-based organic small molecule hole transport materials, the reaction process is shown below, and the specific steps are as follows:

[0025]

[0026] Synthesis of intermediate (I): At room temperature, 2,7-dibromo-9-fluorenone (3.31 g, 9.85 mmol), phenol (3.76 g, 40.00 mmol), and methanesulfonic acid (2 ml, 30.85 mmol) were added sequentially to a two-necked flask. 15 ml of dry carbon tetrachloride was added to the flask under an argon atmosphere, and the reaction was carried out at 80 °C for 48 h. After the reaction was complete, the mixture was cooled to room temperature, and then a saturated sodium bicarbonate solution was added to the reaction solution for neutralization. The reaction solution was then poured into deionized water and extracted with ethyl acetate. The extracted organic phase was dried over anhydrous sodium sulfate and filtered. The filtrate was subjected to rotary evaporation to remove the solvent, yielding the crude product. The crude product was purified by column chromatography using petroleum ether and ethyl acetate (v:v = 4:1) as eluents, yielding a white intermediate (I) in 79% yield. 1 H NMR (400MHz, d6-DMSO, ppm) δ = 9.43 (s, 2H), 7.90 (d, J = 8.1Hz, 2H), 7.58 (dd, J = 8 .1Hz,4H),7.50(d,J=1.6Hz,2H),6.90(d,J=8.6Hz,4H),6.68(d,J=8.7Hz,4H). 13 C NMR (100MHz, d6-DMSO, ppm) δ = 156.90, 154.38, 138.02, 134.95, 131.10, 129.13, 129.07, 123.21, 121.61, 115.79, 64.48.

[0027] Synthesis of intermediate (II): At room temperature, intermediate (I) (2.04 g, 4.03 mmol), 4,4'-dimethoxydiphenylamine (3.66 g, 15.98 mmol), tri-tert-butylphosphine tetrafluoroborate (P(t-Bu)3HBF4) (231 mg, 0.80 mmol), tris(dibenzylacetone)dipalladium (Pd2(dba)3) (173 mg, 0.19 mmol), and sodium tert-butoxide (1.548 g, 15.79 mmol) were added sequentially to a two-necked flask. l) 15 ml of dry toluene was added to a two-necked flask under an argon atmosphere, and the mixture was then refluxed at 110 °C for 18 h. After the reaction was completed, the reaction solution was cooled to room temperature, poured into deionized water, and then extracted with ethyl acetate. The organic phase obtained by extraction was dried with anhydrous sodium sulfate and filtered. The filtrate was evaporated by rotary evaporation to remove the solvent and obtain the crude product. The crude product was purified by column chromatography with petroleum ether and ethyl acetate as eluents (v:v = 4:1) to obtain the yellow intermediate (II) in 54% yield. 1 H NMR (400MHz, d6-DMSO, ppm) δ = 9.31 (s, 2H), 7.50 (d, J = 8.3Hz, 2H), 6.92-6.95 (m, 8H), 6.83- 6.86(m,8H),6.76(d,J=2.0Hz,2H),6.69-6.71(m,6H),6.58(d,J=8.7Hz,4H),3.72(s,12H). 13 C NMR(100MHz,d6-DMSO,ppm)δ=156.34,155.81,152.87,147.47,140.88,136.35, 132.79,129.12,126.45,120.40,119.94,118.49,115.32,115.22,63.64,55.65.

[0028] Synthesis of intermediate (III): At room temperature, intermediate (II) (600 mg, 0.75 mmol), ethyl bromoacetate (4.83 g, 28.92 mmol), and potassium carbonate (2.01 g, 14.56 mmol) were added sequentially to a two-necked flask. Under an argon atmosphere, 40 mL of dry N,N-dimethylformamide was added to the two-necked flask, and the reaction was carried out at 80 °C for 24 h. After the reaction was completed, the reaction solution was cooled to room temperature and the solvent was removed by rotary evaporation. Then, deionized water was added to the reaction mixture and ethyl acetate was added for extraction. The organic phase obtained by extraction was dried with anhydrous sodium sulfate and filtered. The filtrate was removed by rotary evaporation to obtain yellow intermediate (III) in 81% yield. 1H NMR (400MHz, d6-DMSO, ppm) δ = 7.51 (d, J = 8.3Hz, 2H), 6.93-6.95 (m, 8H), 6.77-6.86 (m, 18H), 6.71(dd,J=8.3Hz,2H),4.71(s,4H),4.15(d,J=7.1Hz,4H),3.72(s,12H),1.17-1.20(m,6H). 13 C NMR (100MHz, d6-DMSO, ppm) δ = 169.16, 156.73, 155.87, 152.21, 147.56, 140.77, 138.59, 132.72 ,129.09,126.46,120.55,120.05,118.18,115.25,114.70,65.09,63.62,61.07,55.63,14.46.

[0029] Synthesis of fluorene-based small-molecule hole transport material (Ⅳ): At room temperature, intermediate (Ⅲ) (500 mg, 0.51 mmol) and 50 mL of tetrahydrofuran were added to a single-necked flask. 20 mL of 0.6% lithium hydroxide monohydrate aqueous solution was added dropwise to the flask with stirring, and the reaction was carried out at room temperature for 4 h. After the reaction was completed, 5% hydrochloric acid aqueous solution was added dropwise to the reaction solution until pH = 1. The solution was then extracted with ethyl acetate. The extracted organic phase was dried over anhydrous sodium sulfate and filtered. The filtrate was subjected to rotary evaporation to remove the solvent, yielding the red compound (Ⅳ) in 77% yield. 1 H NMR (400MHz, d6-Acetone, ppm) Figure 1 )δ=7.54(d,J=8.3Hz,2H),6.98-7.01(m,14H),6.81-6.89(m,14H),4.69(s,4H),3.78(d,J=3.6Hz,12H); 13 CNMR (100MHz, d6-Acetone, ppm) Figure 2 )δ=205.48,169.37,156.91,155.98,152.41,138.74,129.17,126.09,199 .81,118.62,114.64,114.12,64.50,63.76,54.84.HRMS-ESI(m / z):[M+H] + Calcd for(C 57 H 49 N2O 10 ): 921.3309, found: 921.3377.

[0030] The UV-Vis absorption spectrum of fluorene-based organic small molecule hole transport materials is visible. Figure 3 The results show that fluorene-based organic small molecule hole transport materials do not exhibit strong absorption in the visible light region, indicating that fluorene-based organic small molecule hole transport materials do not compete with perovskites for light.

[0031] Cyclic voltammetry curves of fluorene-based organic small molecule hole transport materials are visible. Figure 4 The HOMO energy level of the fluorene-based organic small molecule hole transport material was measured to be -5.11 eV by cyclic voltammetry, and the LUMO energy level of the fluorene-based organic small molecule hole transport material was calculated to be -2.19 eV by UV-Vis absorption spectroscopy. This indicates that the energy level of the fluorene-based organic small molecule hole transport material meets the requirements for the fabrication of perovskite solar cell devices.

[0032] Example 2

[0033] The fluorene-based organic small molecule hole transport material synthesized in Example 1 was used as a hole transport material in a perovskite solar cell device. Its specific structure is: FTO / fluorene-based organic small molecule hole transport material / perovskite active layer / electron transport layer / Au.

[0034] The FTO glass was first ultrasonically washed with water, then sequentially cleaned with deionized water, acetone, and ethanol. After drying, a solution of fluorene-based organic small molecule hole transport material was spin-coated onto the FTO glass surface and annealed. Next, a perovskite active layer and an electron transport layer were spin-coated on the side of the fluorene-based organic small molecule hole transport material away from the FTO glass. Finally, Au was deposited as the back electrode, completing the fabrication of the perovskite solar cell device with an effective area of ​​0.12 cm². 2 .

[0035] Using a xenon lamp solar simulator, the light source intensity was tested at AM 1.5G (100mW / cm²). 2 The open-circuit voltage, short-circuit current, and fill factor of the fabricated solar cell device were tested. The perovskite solar cell device was fabricated and characterized according to the above procedure. The current-voltage (JV) characteristic curve of the perovskite solar cell device is shown below. Figure 5 As shown, the open-circuit voltage (Voc) of the battery based on fluorene-based organic small molecule hole transport material (Ⅳ) is 1.05V, and the short-circuit current (Jsc) is 24.79mA / cm. 2 The fill factor (FF) is 76.70%, and the power conversion efficiency (PCE) is 20.03%. The open-circuit voltage (Voc) of the perovskite solar cell device based on the widely used phosphonate-carbazole organic small molecule 2PACz as the hole transport material is 1.13V, and the short-circuit current (Jsc) is 21.89mA / cm². 2The fill factor (FF) is 66.03% and the PCE is 16.36%. These results show that perovskite solar cell devices using fluorene-based small molecule hole transport materials have better electrochemical performance.

[0036] The above are merely preferred embodiments of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A fluorene-based organic small molecule hole transport material, characterized in that, The general structural formula is as follows: ； Where n = 1 - 4, R is , .

2. The fluorene-based organic small molecule hole transport material as described in claim 1, characterized in that, The structural formula is: 。 3. The method for preparing a fluorene-based organic small molecule hole transport material according to claim 1 or 2, characterized in that, Its reaction formula is: .

4. The application of the fluorene-based organic small molecule hole transport material as described in claim 1 or 2 as a hole transport material in the fabrication of perovskite solar cell devices.

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