Synthesis of an organic phosphonic small molecule material for hole transport and its application in perovskite solar cells

Abstract

The application belongs to the technical field of solar cells, and relates to synthesis of an organic phosphonic acid small-molecule material for hole transport and application of the small-molecule material in a perovskite solar cell. The small-molecule material takes imidobenzyl as a central core, takes a n-butyl alkyl chain as a connecting part, and takes a phosphonic acid group as an end group. Through more sufficient electron delocalization space, not only the coordination with the perovskite is strengthened, the hole transport capacity is improved, but also the perovskite surface defects are effectively passivated, and the charge transport capacity with the ITO substrate is enhanced. The phosphonic acid small-molecule material has a simple and reliable preparation method, can be used to prepare a high-efficiency perovskite solar cell at low cost, and has wide application prospect and market potential.

Description

Technical fields:

[0001] This invention belongs to the field of solar cell material technology, specifically relating to the synthesis of an organophosphonic acid small molecule material for hole transport and its application in perovskite solar cells. The design uses an iminodibenzyl as the central core, an n-butylalkyl chain as the connecting part, and a phosphate group as the end group to form an organophosphonic acid small molecule, which is then used as a hole transport layer material in inverted perovskite solar cells. Background technology:

[0002] Perovskite solar cells (PSCs), as a third-generation solar cell technology, are gradually becoming the focus of the solar cell field due to their high energy conversion efficiency, low cost, and environmental friendliness.

[0003] Inverted perovskite solar cells are attracting widespread attention from academia and industry due to their advantages such as high stability, high efficiency, low cost, low-temperature fabrication, and compatibility with tandem cell structures. The low hysteresis, low-temperature fabrication capability, and long-term operational stability of inverted perovskite solar cells facilitate large-scale industrial production.

[0004] Traditional inverted perovskite solar cells primarily use poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and nickel oxide (NiOx) as hole transport layer (HTL) materials. PEDOT:PSS offers advantages such as excellent conductivity, high transmittance, good energy level matching with perovskite materials, and compatibility with flexible photovoltaic devices via low-temperature annealing processes. However, it also suffers from problems such as low interfacial hole separation and transport rate, acid corrosion, and susceptibility to dissolution by perovskite precursor solutions. NiOx possesses a stable crystal structure and is non-corrosive, resulting in high optical and thermal stability for the corresponding PSCs. Meanwhile, nickel oxide also exhibits good high hole mobility and excellent hole extraction capability. However, due to the large band gap of nickel oxide, the Fermi level mismatch between NiOx and the perovskite absorber layer leads to a relatively large energy level shift at the interface after contact, resulting in a weak built-in electric field. Furthermore, low-temperature prepared NiOx films are prone to defects, which increase the chance of carrier recombination, thereby reducing hole collection efficiency. Summary of the Invention:

[0005] This invention addresses the shortcomings of traditional hole transport layers in perovskite solar cells by providing an organophosphonic acid small molecule material (YG32) as a hole transport layer. This small molecule possesses suitable energy levels and functional groups to improve the efficiency and stability of perovskite solar cells. Its molecular structure is as follows:

[0006]

[0007] The aromatic phosphonic acid small molecule material involved in this invention is designed with iminodibenzyl as the central core, n-butylalkyl chain as the linking part, and phosphate group as the end group.

[0008] This invention also provides a method for preparing the aforementioned organophosphonic acid small molecule material, the specific steps of which are as follows:

[0009] (1) Add iminodibenzyl, 0.66 g tetrabutylbromosilane, 1,4-dibromobutane, sodium hydroxide and ultrapure water to a single-necked flask; evacuate, purge with nitrogen, and repeat the evacuation and venting process three times; heat to 50-90℃ for reaction; after the reaction, remove excess tetrabutylbromosilane by extraction; then purify by silica gel column chromatography (dichloromethane: petroleum ether = 1:4) to obtain a white solid, which is 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene;

[0010] (2) Add 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene and triethyl phosphite to a single-necked flask; evacuate, purge with nitrogen, and repeat the evacuation and purging process three times; heat to 120-180℃ for reaction; after the reaction is complete, remove excess triethyl phosphite by vacuum distillation; then purify by silica gel column chromatography (dichloromethane:methanol = 100:1) to obtain a colorless liquid, which is diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate;

[0011] (3) Diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate, trimethylbromosilane and 1,4-dioxane were placed in a single-necked flask; vacuum was drawn, nitrogen was introduced, and the process of evacuation and venting was repeated three times; methanol was added to quench the gas, and the mixture was stirred; ultrapure water was added to hydrolyze the mixture, and the mixture was stirred; finally, a white powder was obtained by vacuum filtration, which was (4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate, which is an organophosphonic acid small molecule material.

[0012] The present invention also provides the application of the organophosphonic acid small molecule material as a hole transport layer in perovskite solar cell devices.

[0013] The present invention also provides a perovskite solar cell, the perovskite solar cell comprising a transparent conductive glass, a hole transport layer, a perovskite layer, an electron transport layer and a metal electrode stacked together, wherein the hole transport layer is the organophosphonic acid small molecule material.

[0014] The present invention also provides a photovoltaic cell, including the perovskite solar cell described above.

[0015] The design concept and advantages of this invention are as follows:

[0016] 1. In terms of structure, the novel phosphonic acid molecule prepared by the present invention (1) has an iminodibenzyl as the central core, which has a larger electron delocalization compared with the common carbazole group central core. Therefore, it has a more significant stability improvement for the electron-rich conjugated central core containing ammonia, and is also conducive to the regulation of molecular energy levels; (2) the co-matching n-butylalkyl chain as the linker provides more configuration adjustment space for the molecular self-assembly process, which is conducive to better adaptation of the molecule to perovskite and more dense film formation, thereby improving the overall device performance; (3) the phosphate group as the end group has a tighter connection with ITO, which is conducive to hole extraction.

[0017] 2. The heteroatom phosphonic acid small molecule material of the present invention has a wide bandgap, good film-forming properties, low synthesis cost, mild preparation conditions, and simple synthesis route, thereby reducing the cost of optimizing perovskite devices.

[0018] 3. The material prepared in this invention, as a hole transport material, greatly improves the efficiency of perovskite solar cells. It achieves excellent device performance and extends the lifespan of perovskite solar cells under high-temperature and light-irradiation conditions; its photoelectric conversion efficiency exceeds 24%, which is expected to facilitate commercial development.

[0019] In summary, this invention proposes an effective conjugation modification strategy to design a novel phosphonic acid small molecule. Through more abundant electron delocalization space, it not only strengthens the coordination with perovskite and improves hole transport capability, but also effectively passivates perovskite surface defects, enhancing charge transport capability with the ITO substrate. The preparation method of this phosphonic acid small molecule material is simple and reliable, enabling the low-cost fabrication of high-efficiency perovskite solar cells, and has broad application prospects and market potential. Attached image description:

[0020] Figure 1 Synthesis route diagram of YG32, a heteroatom phosphonic acid material prepared in Example 1.

[0021] Figure 2 The heteroatom phosphonic acid material YG32 prepared in Example 1 1 H NMR

[0022] Figure 3 JV diagram of perovskite solar cells based on hybrid YG32 phosphonic acid material in this invention Detailed implementation method:

[0023] The technical solution of the present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings.

[0024] Example 1:

[0025] This embodiment relates to a method for preparing organophosphonic acid small molecule materials for hole transport, specifically a method for preparing conjugated phosphonic acid small molecule material (4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl)phosphoric acid (YG32), comprising the following three steps:

[0026] (1) Place 1g of iminodibenzyl into a 250mL single-necked flask, then add 0.66g of tetrabutylbromosilane (TBAB), 15mL of 1,4-dibromobutane, 1.024g of sodium hydroxide (NaOH) and 2mL of ultrapure water; evacuate, purge with nitrogen, and repeat the evacuation and venting process three times; heat to 70℃ and react for 24h; after the reaction, remove excess tetrabutylbromosilane by extraction; then purify by silica gel column chromatography (dichloromethane: petroleum ether = 1:4) to obtain 0.83g of white solid, which is 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene;

[0027]

[0028] (2) 0.83 g of 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene was placed in a 250 mL single-necked flask and 15 mL of triethyl phosphite was added; the evacuation was carried out under vacuum and nitrogen was introduced, and the process was repeated three times; the temperature was raised to 150 °C and the reaction was carried out for 24 h; after the reaction was completed, excess triethyl phosphite was removed by vacuum distillation at 150 °C; the product was then purified by silica gel column chromatography (dichloromethane:methanol = 100:1) to obtain 0.65 g of colorless liquid, which was diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate;

[0029]

[0030] (3) 0.65 g of diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate was placed in a 250 mL single-necked flask, and 5 mL of trimethylbromosilane and 20 mL of 1,4-dioxane were added. The flask was evacuated and filled with nitrogen. The evacuation and venting were repeated three times. 10 mL of methanol was added to quench the reaction. After stirring for 2 h, 50 mL of ultrapure water was added for hydrolysis and stirred for 1 h. Finally, 630 mg of white powder was obtained by vacuum filtration. The white powder was confirmed by 1H NMR spectroscopy to be (4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate (denoted as YG32).

[0031]

[0032] The final product YG32 was subjected to 1The results of H NMR characterization are as follows Figure 2 As shown.

[0033] Example 2:

[0034] This embodiment relates to the fabrication and photovoltaic performance testing of a perovskite solar cell device based on YG32 synthesized in Example 1.

[0035] The fabricated perovskite solar cell device is a pin system consisting of five parts: a transparent conductive glass substrate (ITO) covered with indium tin oxide (ITO), a hole transport layer, a perovskite layer, an electron transport layer, and a metal electrode. The specific fabrication method is as follows: First, the ITO was sequentially cleaned in an ultrasonic apparatus using ultrapure water, ethanol, acetone, and isopropanol. Then, a YG32 thin film was prepared on the ITO surface as the hole transport layer using spin coating (YG32 was dissolved in chlorobenzene at a concentration of 10 mg / mL). The spin coating parameters were 3000 r / min. The spin coating speed is 1000 r / 30 s. After spin coating of the hole transport layer, the wafer is annealed at 150 °C for 30 min. After annealing, ozone cleaning is performed for 10 min. Next, the wafer is placed in a glove box with a humidity of 40% and purged 3 times. The perovskite layer is prepared using the anti-solvent spin coating method. After the process, each device is annealed at 150 °C for 10 min with a humidity of 20-30%. After annealing, the wafer turns gray and is placed back in the glove box. The passivation layer is then spin coated. After the passivation layer is spin coated, the PCBM film and silver electrode are deposited sequentially using the vapor deposition method.

[0036] After fabrication, the performance of the solar cells was tested. A solar cell fabricated using nickel oxide as the hole transport layer material served as a control group.

[0037] The current-voltage (JV) characteristic curves of its battery device performance are shown in the figure. Figure 3 And Table 1. From Figure 3 As shown in Table 1, in perovskite devices, the open-circuit voltage V of the YG32 hole transport layer is... OC The voltage is 1.20V, and the short-circuit current density is J. SC 22.84 mA / cm 2 The fill factor (FF) is 86.54%, and the photoelectric conversion efficiency (PCE) is 23.72%, which improves the device efficiency and device stability.

[0038] Table 1 Device Performance

[0039]

Claims

1. An organophosphonic acid small molecule material, characterized in that, Using iminodibenzyl as the central core, n-butylalkyl chains as the linking parts, and phosphate groups as end groups, its specific structure is as follows:

2. The method for preparing the organophosphonic acid small molecule material according to claim 1, characterized in that, The specific steps include: (1) Add iminodibenzyl, 0.66 g tetrabutylbromosilane, 1,4-dibromobutane, sodium hydroxide and ultrapure water to a single-necked flask; evacuate, purge with nitrogen, and repeat the evacuation and purging process three times; heat to 50-90℃ for reaction; after the reaction is complete, remove excess tetrabutylbromosilane by extraction; then purify by silica gel column chromatography to obtain a white solid, which is 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene; (2) Add 5-(4-bromobutyl)-10,11-dihydro-5H-dibenzo[b,f]azanaphthalene and triethyl phosphite to a single-necked flask; evacuate, purge with nitrogen, and repeat the evacuation and purging process three times; heat to 120-180℃ for reaction; after the reaction is complete, remove excess triethyl phosphite by vacuum distillation; then purify by silica gel column chromatography to obtain a colorless liquid, which is diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate; (3) Diethyl(4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate, trimethylbromosilane and 1,4-dioxane were placed in a single-necked flask; vacuum was drawn, nitrogen was introduced, and the process of evacuation and venting was repeated three times; methanol was added to quench the gas, and the mixture was stirred; ultrapure water was added to hydrolyze the mixture, and the mixture was stirred; finally, a white powder was obtained by vacuum filtration, which was (4-(10,11-dihydro-5H-dibenzo[b,f]azanaphthalene-5-yl)butyl) phosphate, which is an organophosphonic acid small molecule material.

3. The application of the organophosphonic acid small molecule material of claim 1 as a hole transport layer in perovskite solar cell devices.

4. A perovskite solar cell, characterized in that, The perovskite solar cell comprises a transparent conductive glass, a hole transport layer, a perovskite layer, an electron transport layer, and a metal electrode stacked together, wherein the hole transport layer is the organophosphonic acid small molecule material as described in claim 1.

5. A photovoltaic cell, characterized in that, Including the perovskite solar cell of claim 4.

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