Method for improving light absorption and ultraviolet stability of perovskite solar cell

Abstract

The invention discloses a method for improving light absorption and ultraviolet stability of a perovskite solar cell, and belongs to the technical field of perovskite solar cell preparation. According to the technical scheme, 2, 4, 5, 6-tetra (9-carbazolyl)-isophthalonitrile is added into a light active layer of the trans-perovskite solar cell. The 2, 4, 5, 6-tetra (9-carbazolyl)-isophthalonitrile molecule has a strong absorption peak in an ultraviolet light wave band and emits a wide emission peak in a visible light region, so that the perovskite material can absorb more visible light and filter out ultraviolet light unfavorable for the visible light, the ultraviolet stability of the perovskite solar cell is remarkably improved, the method is simple and efficient, and the method is suitable for industrial production. The popularization and application prospects are wide.

Description

Technical Field

[0001] The invention belongs to the technical field of perovskite solar cell preparation, and in particular relates to a method for improving the light absorption and ultraviolet stability of a perovskite solar cell. Background Art

[0002] Perovskite solar cells (PSCs) are solar cells that use perovskite-type organometallic halide semiconductors as light-absorbing materials. In 2009, Miyasaka et al. first applied perovskite-type organometallic halide as a sensitizer to solar cells, with an initial photoelectric conversion efficiency of only 3.8%. After more than a decade of rapid development, its efficiency has been greatly improved to 26.7%, close to the level of current commercial single-crystalline silicon cells. This amazing efficiency improvement makes perovskite solar cells one of the most promising devices to replace crystalline silicon cells. However, point defects inside perovskite materials, as well as surface and grain boundary defects, easily capture electrons or holes, leading to non-radiative recombination, which significantly affects their photoelectric performance. In addition, severe damage caused by ultraviolet rays and limitations in the use of the solar spectrum further pose major challenges to improving the performance of perovskite solar cells.

[0003] It is well known that commonly used metal halide perovskites have narrow direct band gaps and can efficiently absorb light in the visible range. However, the visible light that perovskite materials can efficiently utilize only accounts for 45%-50% of the total energy of incident sunlight, while the rest is in the ultraviolet (UV) and infrared regions. Although some longer wavelength ultraviolet light (300-390 nm) can be partially utilized by perovskite materials, high-energy short-wave ultraviolet light is not only difficult to be absorbed, but also leads to intra-band energy loss and photon waste. This waste further triggers the hot carrier thermalization effect and may accelerate the decomposition of perovskite materials. More seriously, ultraviolet radiation usually inevitably has an adverse effect on the long-term photostability of perovskite materials. This is because ultraviolet light can induce chemical reactions in the material, accelerate the migration of volatile organic cations and halogen ions, and thus cause defect-related degradation problems. Although encapsulation technology is effective in blocking oxygen and moisture penetration, it is still difficult to completely eliminate the negative effects of ultraviolet radiation in the use environment. Therefore, how to simultaneously enhance the light absorption capacity and stability of perovskite materials against ultraviolet radiation has become a key issue that needs to be solved urgently. At present, down-conversion technology has become one of the most commonly used technologies for achieving light management of perovskite solar cells due to its excellent tunability in expanding the absorption spectrum. Current light conversion materials are mainly concentrated on lanthanide materials. Although lanthanides have shown many advantages in optoelectronic applications, their high cost, poor solubility, decreased optical efficiency and potential environmental toxicity remain the main challenges for their practical application. Therefore, it is particularly important to develop alternative materials with similar photon conversion functions that can overcome the above limitations. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the light absorption and ultraviolet stability of perovskite solar cells. For the first time, it is proposed to use TADF molecules 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile (4CzIPN) as an additive in trans-perovskite solar cells. The light conversion effect of 4CzIPN filters ultraviolet rays and improves the light absorption rate of the perovskite layer. At the same time, it can also assist crystallization and passivate defects.

[0005] To achieve the above object, the present invention adopts the following technical solution: A method for using TADF molecules to improve the light absorption and UV stability of perovskite solar cells: 4CzIPN molecules are introduced as additives in the photoactive layer of an inverse perovskite solar cell device.

[0006] The concentration of the 4CzIPN additive is 1-5 mg / mL.

[0007] Add 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile to 1.5 M FA 0.93 Cs 0.05 MA 0.02 PbI 0.98 Br 0.02 The perovskite precursor solution was spin-coated on NiO at a speed of 5000 rpm / s. x / Me-4PACz double hole transport layer substrate, and then heated and annealed at 120 ° C to form a perovskite photoactive layer, and then PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0008] The beneficial effects of the present invention are as follows: 4CzIPN is used as an additive in perovskite photovoltaic devices. In terms of light conversion, 4CzIPN converts ultraviolet light into visible light for perovskite absorption and utilization through Förster energy transfer. In terms of crystal growth, 4CzIPN combines with PbI2 to form a more favorable intermediate phase and induces better crystallization of perovskite, inhibiting the generation of residual stress. In terms of defect passivation, 4CzIPN effectively inhibits the positively charged Pb 2+ Defects and ion migration. In terms of stability, the introduction of 4CzIPN reduces the damage of ultraviolet light to the film and anchors the components of the perovskite, which greatly improves the stability of the device to ultraviolet light and humidity. Therefore, the use of TADF molecule 4CzIPN as an additive to modify perovskite is a simple, feasible and efficient strategy that can significantly improve the performance of perovskite solar cells and enhance their ultraviolet light and humidity stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is the structural formula and stick model of the 4CzIPN molecule; Figure 2 It is the UV-visible absorption spectrum and emission spectrum of 4CzIPN molecule; Figure 3 is the steady-state PL spectra of perovskite films based on glass substrates before and after 4CzIPN modification; Figure 4 It is the XRD spectra of pure 4CzIPN, pure PbI2 and mixed PbI2-4CzIPN powder; Figure 5 is the SEM image of the perovskite film before and after 4CzIPN modification; Figure 6 This is a schematic diagram of the basic structure of a perovskite solar cell modified with 4CzIPN and the corresponding JV curve; Figure 7 is the XRD spectra of the perovskite film before and after 4CzIPN modification under UV irradiation aging; Figure 8 It is a long-term performance stability test of perovskite solar cells before and after 4CzIPN modification. DETAILED DESCRIPTION

[0010] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0011] Example 1 In the glove box, accurately weigh 1 mg of 4CzIPN additive and dissolve it in 1 mL of perovskite precursor solvent (DMF and DMSO) to ensure uniform dissolution. Add perovskite precursor materials (such as PbI2, PbBr2, FAI, CsI, MABr, MACl, etc.) in a fixed ratio, stir and shake thoroughly to dissolve, and prepare a 1 mg / mL concentration of 4CzIPN perovskite precursor solution. Make the solution transparent and uniform and filter it with a filter membrane to remove impurities. Then spin coat it on the NiOx / Me-4PACz double hole transport layer substrate at a speed of 5000 rpm / s, anneal it on a hot plate at 120°C for 20 min to form a perovskite photoactive layer, and then continue to deposit PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0012] Example 2 In the glove box, accurately weigh 2 mg of 4CzIPN additive and dissolve it in 1 mL of perovskite precursor solvent (DMF and DMSO) to ensure uniform dissolution. Add perovskite precursor materials (such as PbI2, PbBr2, FAI, CsI, MABr, MACl, etc.) in a fixed ratio, stir and shake thoroughly to dissolve, and prepare a 2 mg / mL concentration of 4CzIPN perovskite precursor solution. Make the solution transparent and uniform and filter it with a filter membrane to remove impurities. Then spin coat it on the NiOx / Me-4PACz double hole transport layer substrate at a speed of 5000 rpm / s, anneal it on a hot plate at 120°C for 20 min to form a perovskite photoactive layer, and then continue to deposit PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0013] Example 3 In the glove box, accurately weigh 3 mg of 4CzIPN additive and dissolve it in 1 mL of perovskite precursor solvent (DMF and DMSO) to ensure uniform dissolution. Add perovskite precursor materials (such as PbI2, PbBr2, FAI, CsI, MABr, MACl, etc.) in a fixed ratio, stir and shake thoroughly to dissolve, and prepare a 3 mg / mL concentration of 4CzIPN perovskite precursor solution. Make the solution transparent and uniform and filter it with a filter membrane to remove impurities. Then spin coat it on the NiOx / Me-4PACz double hole transport layer substrate at a speed of 5000 rpm / s, anneal it on a hot plate at 120°C for 20 min to form a perovskite photoactive layer, and then continue to deposit PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0014] Example 4 In the glove box, accurately weigh 4 mg of 4CzIPN additive and dissolve it in 1 mL of perovskite precursor solvent (DMF and DMSO) to ensure uniform dissolution. Add perovskite precursor materials (such as PbI2, PbBr2, FAI, CsI, MABr, MACl, etc.) in a fixed ratio, stir and shake thoroughly to dissolve, and prepare a 4 mg / mL concentration of 4CzIPN perovskite precursor solution. Make the solution transparent and uniform and filter it with a filter membrane to remove impurities. Then spin coat it on the NiOx / Me-4PACz double hole transport layer substrate at a speed of 5000 rpm / s, anneal it on a hot plate at 120°C for 20 min to form a perovskite photoactive layer, and then continue to deposit PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0015] Example 5 In the glove box, accurately weigh 5 mg of 4CzIPN additive and dissolve it in 1 mL of perovskite precursor solvent (DMF and DMSO) to ensure uniform dissolution. Add perovskite precursor materials (such as PbI2, PbBr2, FAI, CsI, MABr, MACl, etc.) in a fixed ratio, stir and shake thoroughly to dissolve, and prepare a 5 mg / mL concentration of 4CzIPN perovskite precursor solution. Make the solution transparent and uniform and filter it with a filter membrane to remove impurities. Then spin coat it on the NiOx / Me-4PACz double hole transport layer substrate at a speed of 5000 rpm / s, anneal it on a hot plate at 120°C for 20 min to form a perovskite photoactive layer, and then continue to deposit PC 61 BM and BCP serve as electron transport layer and barrier layer, respectively, and finally a metal Ag electrode is evaporated to obtain a complete perovskite solar cell device.

[0016] Photoelectric performance test: Test the photoelectric conversion performance under the AM 1.5G standard solar simulator; Figure 1 The structural formula and ball-and-stick model of 4CzIPN, which contains multiple donor carbazole (-Cz) groups and a few acceptor groups (-CN), makes the -CN electron-rich, so that it can better combine with the positively charged lead defects in the perovskite for passivation. Figure 2 Figure 3 is the structural diagram of the 4CzIPN molecule and its UV-visible absorption and emission spectra. It can be observed that the molecule has a strong absorption peak in the ultraviolet light band and a broad emission peak in the visible light region. The visible light it emits can be further absorbed and utilized by perovskite, while the ultraviolet light that is unfavorable to perovskite is filtered out accordingly. Figure 3 The steady-state PL spectra of the blank group and the 4CzIPN-modified group of perovskite films based on glass substrates. Since 4CzIPN, as a TADF molecule, has the effect of reverse intersystem crossing (RISC), it can emit delayed fluorescence with a longer time and can provide more additional visible light photons for the perovskite layer. Therefore, the perovskite film modified with 4CzIPN molecules can generate more photogenerated carriers, and the PL intensity generated by the correspondingly modified perovskite film based on the glass substrate is also stronger. Figure 4The XRD spectra of pure 4CzIPN, pure PbI2 and mixed PbI2-4CzIPN powders are shown. The results show that the mixed powder has a new diffraction signal compared to the pure 4CzIPN powder, and the characteristic peak at 12.8° still exists relative to the pure PbI2 sample, but the intensity is weakened. This indicates that there is a strong bonding interaction between 4CzIPN and PbI2, indicating that the molecule can passivate positively charged lead defects in the perovskite film and effectively anchor the PbI2 component during the subsequent operation of the battery to prevent lead leakage. Figure 5 a and 5b are SEM images of the perovskite film before and after modification. It can be observed that the modified perovskite film becomes smoother and has a larger grain size, indicating that the molecule also plays a certain regulatory role in the growth of perovskite crystals. Figure 6 a is a schematic diagram of the basic structure of an inverted perovskite solar cell. Figure 6 b is the JV curve of the corresponding device. The photoelectric conversion efficiency obtained increased from 22.82% of the blank group to 24.23% of the modified group, and the photoelectric performance was greatly improved. Figure 7 The XRD spectra of the perovskite film before and after 4CzIPN modification under ultraviolet light aging. The results show that the PbI2 produced by the modified perovskite film after ultraviolet light treatment is greatly reduced, indicating that 4CzIPN can effectively improve the UV resistance of perovskite and greatly improve the photostability. Figure 8 The long-term performance stability of perovskite solar cells before and after 4CzIPN modification shows that the unencapsulated device after modification exhibits excellent moisture resistance. After being stored in an air environment (25℃±5℃, 15±5% RH) for 1680 hours, it can still maintain 90% of the original efficiency, and its moisture resistance is greatly improved. Therefore, the use of TADF molecule 4CzIPN as an additive to modify perovskite is a simple, feasible and efficient strategy that can significantly improve the performance of perovskite solar cells and enhance their UV and humidity stability.

[0017] The above description is only a preferred embodiment of the present invention. All perovskite additive modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for improving light absorption and UV stability of perovskite solar cells, characterized in that: 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile is added to the photoactive layer of the inverse perovskite solar cell.

2. The method according to claim 1, characterized in that: The concentration of 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile in the photoactive layer is 1-5 mg / mL.

3. The method according to claim 1, characterized in that: Add 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile to 1.5 M FA 0.93 Cs 0.05 MA 0.02 PbI 0.98 Br 0.02 The perovskite precursor solution was spin-coated on NiO at a speed of 5000 rpm / s. x / Me-4PACz double hole transport layer substrate and annealed at 120°C to form a perovskite photoactive layer.

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