A perovskite photovoltaic device based on self-assembled monolayer and its fabrication method

Abstract

This invention discloses a perovskite photovoltaic device based on a self-assembled monolayer and its fabrication method. The perovskite photovoltaic device includes an anode substrate, and sequentially disposed on one side of the anode substrate are a self-assembled monolayer, a perovskite light-absorbing layer, an electron transport layer, a hole-blocking layer, and a cathode electrode. The material of the self-assembled monolayer contains methylthio-substituted groups, with a carbazole moiety as the parent core and a phosphonic acid moiety as the anchoring group. This invention provides a novel method for the molecular design of SAM materials and provides a highly versatile functional substituent group. The perovskite photovoltaic device based on MeS-CbzPh prepared by this invention achieves a power conversion efficiency of 26.01% and maintains an efficiency of 93.3% after 1000 hours of continuous operation at maximum power point tracking, demonstrating excellent stability.

Description

Technical Field

[0001] This invention relates to the field of perovskite photovoltaic device technology, specifically to a perovskite photovoltaic device based on a self-assembled monolayer and its fabrication method. Background Technology

[0002] Perovskite solar cells (PSCs) are divided into two categories: nip (front-mounted) and pin (reverse-mounted) devices. Pin-mounted PSCs have attracted widespread attention due to their lower processing temperature and good compatibility with flexible and tandem solar cells. Significant progress has been made in the power conversion efficiency (PCE) of pin-mounted PSCs due to the development and use of self-assembled monolayers (SAMs) as hole transport layers. This is because SAMs provide tunable energy levels, passivate defects at the buried interface of perovskites, and are inexpensive to synthesize. High-performance SAM materials often incorporate methoxy (MeO-) groups, such as (2-(3,6-dimethoxycarbazole-9-yl)ethyl)phosphonic acid (MeO-2PACz) and (4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl)phosphonic acid (MeO-4PACz). The methoxy group not only effectively enhances the wettability between SAM and the perovskite layer, but also passivates defects at the buried interface, thereby improving device performance. However, due to the strong electron-donating ability of the methoxy group, the highest occupied molecular orbital (HOMO) of the SAM material is significantly shallower, resulting in a mismatch between the HOMO energy level and that of the perovskite layer. Therefore, finding a substitute group that can retain all the advantages of the methoxy group while achieving a better match for the HOMO energy level is a key strategy for further improving the performance of inverted PSCs. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a perovskite photovoltaic device based on a self-assembled monolayer and its preparation method, and to provide a multifunctional substituent—methylthio (MeS-) substituent—as a substitute for traditional methoxy groups in basic SAM materials.

[0004] This invention is achieved through the following technical solution:

[0005] A perovskite photovoltaic device based on a self-assembled monolayer includes an anode substrate, and a self-assembled monolayer, a perovskite light-absorbing layer, an electron transport layer, a hole-blocking layer, and a cathode electrode are sequentially disposed on one side of the anode substrate. The structural formula of the material of the self-assembled monolayer is shown in formula (I):

[0006]

[0007] Where n is an integer from 0 to 10, Ar1 is a benzene ring or a naphthalene ring, Ar2 is a benzene ring or a naphthalene ring, R1 is a methylthio group or hydrogen, R2 is a methylthio group or hydrogen, and R1 and R2 are not both hydrogen.

[0008] The perovskite photovoltaic device provided by this invention is an inverted device. The self-assembled monolayer material contains methylthio (MeS-) substituents, with a carbazole moiety as the parent core and a phosphonic acid moiety as the anchoring group. The inventors discovered that lead ions are a soft acid with a large ionic radius and low charge density. Sulfur atoms, as a soft base, have a larger atomic radius than oxygen atoms and lower electronegativity. Therefore, the outermost electrons of sulfur atoms can move more freely into the soft acid, forming stronger Pb-S bonds. Thus, the methylthio group can more effectively passivate the buried interface of the perovskite. Furthermore, due to the weak electron-donating ability of the methylthio group, the methylthio-based SAM material exhibits better HOMO energy level matching with perovskite. The interface between perovskite and the methylthio-based SAM material achieves more efficient charge transport, mitigating the problem of reverse charge accumulation. Ultimately, this invention significantly improves the efficiency and stability of PSCs.

[0009] Furthermore, the structural formula of the self-assembled monolayer material is selected from:

[0010]

[0011] Formula (II) is 4-(10-methylthio-7H-benzo[c]carbazole-7-yl)butylphosphonic acid (MeS-CbzPh); Formula (III) is 4-(3,6-bis(methylthio)-9H-carbazole-9-yl)butylphosphonic acid (MeS-4PACz); Formula (IV) is MeS-2PACz; Formula (V) is MeS-4PADCB; Formula (VI) is MeS-2PADCB.

[0012] The methylthio group exhibits high versatility and also demonstrates excellent performance in the more common 4PACz series SAM materials.

[0013] A method for fabricating the above-mentioned perovskite photovoltaic device based on a self-assembled monolayer includes the following steps:

[0014] S1. Prepare a self-assembled monolayer on an anode substrate;

[0015] S2. Prepare a perovskite light-absorbing layer on the self-assembled monolayer described in S1;

[0016] S3. An electron transport layer is prepared on the perovskite light-absorbing layer described in S2;

[0017] S4. A hole blocking layer and a cathode electrode are sequentially fabricated on the electron transport layer described in S3 to obtain the perovskite photovoltaic device based on a self-assembled monolayer.

[0018] The preparation method provided by this invention is simple to operate and produces a self-assembled monolayer-based perovskite photovoltaic device with high performance and stable device structure.

[0019] Furthermore, in step S1, the anode substrate includes an indium tin oxide (ITO) substrate or a tin fluoride-doped tin oxide (FTO) substrate, and both ITO and FTO substrates have excellent heat resistance, light transmittance, and flatness.

[0020] In a specific implementation, the synthesis process of MeS-CbzPh in step S1 is as follows:

[0021]

[0022] In a specific implementation, the synthesis process of MeS-4PACz in step S1 is as follows:

[0023]

[0024] In a specific embodiment, in step S1, the anode substrate is cleaned, the cleaned anode substrate is dried, and after ultraviolet treatment, a self-assembled monolayer is coated on the anode substrate.

[0025] Further, in step S1, the self-assembled monomolecular solution is spin-coated onto the anode substrate and annealed to obtain the self-assembled monomolecular layer.

[0026] Furthermore, the method for preparing the self-assembled monomolecular solution is as follows: dissolve the material of the self-assembled monolayer in an organic solvent to obtain the self-assembled monomolecular solution.

[0027] Furthermore, the organic solvent is preferably ethanol.

[0028] Furthermore, the concentration of the self-assembled monomolecular solution is 0.3-1.0 mg / mL.

[0029] Furthermore, the spin coating speed is 3000-4000 rpm, the spin coating time is 20-40 s, the annealing temperature is 100-110℃, and the annealing time is 10-15 min.

[0030] Further, in step S2, the preparation of the perovskite light-absorbing layer includes the following steps: dissolving lead iodide (PbI2), cesium iodide (CsI), formamidinium iodide (FAI), lead bromide (PbBr2) and methylammonium bromide (MABr) in an organic solvent, and obtaining a perovskite precursor solution after reaction; coating the perovskite precursor solution onto the self-assembled monolayer.

[0031] Furthermore, the lead bromide undergoes purification treatment.

[0032] Furthermore, the organic solvent is dimethylformamide (DMF) and / or dimethyl sulfoxide (DMSO), and when DMF and DMSO are used as a mixed solvent, the volume ratio of DMF to DMSO is 4:1.

[0033] Further, in step S2, the perovskite precursor solution is spin-coated onto the self-assembled monolayer, and the perovskite light-absorbing layer is obtained after annealing.

[0034] Furthermore, the spin coating speed is 4000-6000 rpm, and the anti-solvent is added 20-30 seconds after the start of spin coating. After continuing spin coating for 10-20 seconds, the spin coating is annealed at 90-110℃ for 30-60 minutes.

[0035] Furthermore, the antisolvent includes chlorobenzene (CB).

[0036] Furthermore, in step S3, an electron transport layer is prepared by spin coating, with a spin coating speed of 2000-3000 rpm and a spin coating time of 30-50 s.

[0037] Further, in step S3, the material of the electron transport layer includes methyl [6,6]-phenyl C61-butyrate (PCBM).

[0038] In a specific embodiment, in step S3, PCBM is dissolved in chlorobenzene solution to obtain an electron transport layer precursor solution; the electron transport layer precursor solution is spin-coated onto the perovskite light-absorbing layer.

[0039] Furthermore, in step S4, a hole blocking layer and a cathode electrode are prepared sequentially using a thermal evaporation deposition method.

[0040] Furthermore, in step S4, the material of the hole blocking layer includes copper bath (BCP).

[0041] Furthermore, in step S4, the cathode electrode includes a gold (Au) electrode or a silver (Ag) electrode.

[0042] Furthermore, the thickness of the self-assembled monolayer is 3-7 nm, the thickness of the perovskite light-absorbing layer is 500-600 nm, the thickness of the electron transport layer is 40-50 nm, the thickness of the hole blocking layer is 8-10 nm, and the thickness of the cathode electrode is 80-110 nm.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] 1. This invention provides a novel method for the molecular design of SAM materials, and provides a highly versatile functional substituent group. By introducing the methylthio group into SAM materials, this group acts as a regulating bridge, enhancing the interaction with perovskite and achieving better band alignment.

[0045] 2. The inverted perovskite photovoltaic device based on MeS-CbzPh SAM material provided by this invention achieves an optimal PCE of 26.01%. Furthermore, the unencapsulated PSCs exhibit excellent stability during maximum power point tracking, maintaining 93.3% of the initial PCE even after 1000 hours of continuous maximum power point tracking operation. Attached Figure Description

[0046] Figure 1 The diagrams show the chemical structures, electrostatic potential surfaces, and binding energies with perovskites for CbzPh, MeO-CbzPh, and MeS-CbzPh; where a is the chemical structure and electrostatic potential surface diagram, and b is the binding energy data diagram.

[0047] Figure 2 The images show the PL spectrum of the perovskite thin film and the DLCP curve of the perovskite photovoltaic devices in Examples 1 and Comparative Examples 1-2; where a is the PL spectrum and b is the DLCP curve.

[0048] Figure 3 The graph shows the JV performance test results of the perovskite photovoltaic devices in Example 1 and Comparative Examples 1-2.

[0049] Figure 4 The PCE data graphs are for the perovskite photovoltaic devices of Examples 1-2 and Comparative Examples 1-4.

[0050] Figure 5 The graph shows the stability data of maximum power point tracking for the perovskite photovoltaic devices of Example 1 and Comparative Examples 1-2. Detailed Implementation

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0053] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0054] The ITO substrates, lead iodide (PbI2), cesium iodide (CsI), formamidinium iodide (FAI), methylammonium chloride (MACl), lead bromide (PbBr2), methylammonium bromide (MABr), and chlorobenzene (CB) used in the following examples and comparative examples were all purchased from Sigma-Aldrich. Dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and isopropanol (IPA) were purchased from Alfa Aesar Ltd.

[0055] In the following examples and comparative examples, the self-assembled monomolecular solution was prepared by dissolving 0.5 mg of the self-assembled monolayer material in 1 mL of ethanol and stirring at room temperature for 7 hours to obtain the self-assembled monomolecular solution.

[0056] In the following examples and comparative examples, the perovskite precursor solution was prepared by dissolving 620 mg PbI2, 213 mg FAI, 12.4 mg MABr, 43 mg PbBr2 and 11.7 mg CsI in 1 mL of a mixed solvent of DMF and DMSO, wherein the volume ratio of DMF to DMSO was 4:1. The perovskite precursor solution was obtained after stirring at room temperature for 7 hours.

[0057] In the following examples and comparative examples, the electron transport layer solution was prepared by dissolving 20 mg PCBM in 1 mL of chlorobenzene and stirring at room temperature for 7 hours to obtain the electron transport layer precursor solution.

[0058] Example 1

[0059] An inverted perovskite photovoltaic device based on MeS-CBzPh, comprising an ITO substrate, a MeS-CBzPh layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode sequentially disposed on one side of the ITO substrate, is specifically fabricated by the following method:

[0060] S1. Preparation of a 5nm MeS-CBzPh layer on an ITO substrate: The ITO substrate was repeatedly ultrasonically cleaned twice with deionized water, acetone, and ethanol, respectively, and baked for 20 minutes to completely remove the solvent and moisture. It was then treated with ultraviolet light and ozone for 20 minutes to obtain the ITO substrate. The MeS-CBzPh solution was spin-coated onto the ITO substrate, and 70 μL of MeS-CBzPh solution was coated by spin-coating at 3000 rpm for 30 seconds. The substrate was then annealed at 100°C for 10 minutes to obtain the MeS-CBzPh layer.

[0061] S2. Prepare a 500 nm Perovskite layer on the MeS-CBzPh layer described in S1: Place 70 μL of perovskite precursor solution on the MeS-CBzPh layer and spin coat the perovskite precursor solution at 5000 rpm for 25 s. Then add 200 μL of chlorobenzene antisolvent and continue spin coating for 10 s. After spin coating, transfer the solution to a heating stage for annealing. Anneal at 100 °C for 45 min to obtain the Perovskite layer.

[0062] S3. Prepare a 50 nm PCBM layer on the Perovskite layer described in S2: Prepare an electron transport layer by spin coating, coat 70 μL of PCBM solution by standing, and spin coat at 2000 rpm for 30 s to obtain the PCBM layer.

[0063] S4. A BCP layer and an Ag electrode are sequentially prepared on the PCBM layer described in S3: A 10 nm BCP layer and a 100 nm Ag electrode are sequentially prepared by thermal evaporation deposition.

[0064] Example 2

[0065] An inverted perovskite photovoltaic device based on MeS-4PACz (ITO / MeS-4PACz / Perovskite / PCBM / BCP / Ag) includes an ITO substrate, and a MeS-4PACz layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode are sequentially disposed on one side of the ITO substrate. The fabrication method is basically the same as that in Example 1.

[0066] Comparative Example 1

[0067] An inverted perovskite photovoltaic device based on CBzPh, ITO / CBzPh / Perovskite / PCBM / BCP / Ag, includes an ITO substrate, and a CBzPh layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode are sequentially disposed on one side of the ITO substrate. The fabrication method is basically the same as that in Example 1.

[0068] Comparative Example 2

[0069] An inverted perovskite photovoltaic device based on MeO-CBzPh, comprising an ITO substrate, a MeO-CBzPh layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode sequentially disposed on one side of the ITO substrate, is prepared by a method basically the same as in Example 1.

[0070] Comparative Example 3

[0071] An inverted perovskite photovoltaic device based on 4PACz (ITO / 4PACz / Perovskite / PCBM / BCP / Ag) includes an ITO substrate, a 4PACz layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode sequentially disposed on one side of the ITO substrate. The fabrication method is basically the same as in Example 1.

[0072] Comparative Example 4

[0073] An inverted perovskite photovoltaic device based on MeO-4PACz (ITO / MeO-4PACz / Perovskite / PCBM / BCP / Ag) includes an ITO substrate, and a MeO-4PACz layer, a perovskite light-absorbing layer, a PCBM layer, a BCP layer, and an Ag electrode are sequentially disposed on one side of the ITO substrate. The fabrication method is basically the same as that in Example 1.

[0074] Figure 1 This image shows the chemical structures, electrostatic potential surfaces, and binding energies with perovskites for CbzPh, MeO-CbzPh, and MeS-CbzPh; where a represents the chemical structure and electrostatic potential surface diagram, and b represents the binding energy data. CbzPh is used as a SAM control material and is frequently used in inverted devices, exhibiting excellent performance. Figure 1 As shown in Figure a, the calculated electrostatic potential surfaces (ESPs) of these three molecules indicate that both MeO- and MeS- groups generate negative potentials near the aromatic side, with MeS-CbzPh exhibiting the strongest dipole moment. The sulfur in MeS-CbzPh forms a strong coordination interaction with the lead in the perovskite. The binding energies of the three SAM molecules with the perovskite are -0.84 eV, -0.98 eV, and -1.31 eV, respectively. Figure 1As shown in b.

[0075] Figure 2 The figures show the PL spectra of the perovskite thin films in Examples 1 and Comparative Examples 1-2, and the DLCP curves of the perovskite photovoltaic devices; where a is the PL spectrum and b is the DLCP curve. Figure 2 The steady-state photoluminescence (PL) spectrum of perovskite film a shows that the PL peak position remains unchanged at 808 nm, indicating a perovskite bandgap of 1.53 eV. Notably, the PL intensity of the perovskite film on the MeS-CbzPh substrate is significantly enhanced, indicating a reduction in nonradiative recombination and defects at the buried interface of the perovskite film. To verify the reduction in trap density at the buried interface of the treated perovskite film, capacitance-voltage (CV) measurements were performed on devices based on CbzPh, MeO-CbzPh, and MeS-CbzPh under different bias voltages. Figure 2 Figure b shows the drive-stage capacitance distribution (DLCP) curve derived from the CV characteristics. Compared with the original perovskite film, the trap density at the buried interface of the optimized film is significantly reduced.

[0076] Figure 3 The graph shows the JV performance test results of the perovskite photovoltaic devices in Example 1 and Comparative Examples 1-2. The current density-voltage (JV) curves and corresponding efficiencies of the perovskite photovoltaic devices are tested. Figure 3 As can be seen, the CbzPh-based device achieves a PCE of 24.36% and an open-circuit voltage (V). OC The voltage is 1.17V, and the short-circuit current density (J) is... SC The value is 25.62 mA / cm. 2 The fill factor (FF) is 80.29%. Introducing substituents into CbzPh significantly improves the performance of the corresponding devices; devices based on MeO-CbzPh exhibit a PCE of 25.16% and V0.05. OC 1.18V, J SC 26.34 mA / cm 2 The FF is 80.90%; the MeS-CbzPh-based device shows a PCE of 26.01%, V OC 1.19V, J SC 26.43 mA / cm 2 The FF is 81.98%. The improved device performance of the present invention is attributed to the excellent passivation effect and charge transport performance of the methylthio substituent group in MeS-CbzPh.

[0077] Figure 4 The PCE data graphs for the perovskite photovoltaic devices of Examples 1-2 and Comparative Examples 1-4 are shown below. Figure 4As can be seen, the highest PCE of the MeS-4PACz-based device is 24.12%, which is better than the best PCE of 20.41% for the 4PACz-based device and 21.45% for the MeO-4PACz-based device. The improved device performance of this invention is mainly due to the ability of the methylthio group to modulate the HOMO energy level of the 4PACz molecule and its excellent ability to passivate defects at the perovskite buried interface. Similarly, the efficiency of the CbzPh-based devices also shows a consistent trend. The MeS-CbzPh-based device achieves a highest efficiency of 26.01%, exceeding the 24.36% of the CbzPh-based device and the 25.16% of the MeO-CbzPh-based device.

[0078] Figure 5 Maximum power point tracking (MPPT) of the perovskite photovoltaic devices of Examples 1 and 1-2 under simulated continuous sunlight illumination is shown. The MeS-CbzPh-based device exhibits better output stability. The MeO-CbzPh-based and MeS-CbzPh-based devices retained 85.5% and 93.3% of their initial PCE, respectively, after 1000 hours, while the CbzPh-based device dropped to below 77.8%. This superior long-term stability indicates that more effective defect passivation is achieved at the perovskite interface through the incorporation of MeS- groups.

[0079] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A perovskite photovoltaic device based on a self-assembled monolayer, characterized in that, The anode substrate includes a self-assembled monolayer, a perovskite light-absorbing layer, an electron transport layer, a hole-blocking layer, and a cathode electrode sequentially disposed on one side of the anode substrate. The structural formula of the material of the self-assembled monolayer is shown in formula (II): Formula (II); The preparation of the perovskite light-absorbing layer includes the following steps: dissolving lead iodide, cesium iodide, formamidinium iodide, lead bromide and methylammonium bromide in an organic solvent, and obtaining a perovskite precursor solution after reaction; coating the perovskite precursor solution onto the self-assembled monolayer.

2. A method for fabricating a perovskite photovoltaic device based on a self-assembled monolayer as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of a self-assembled monolayer on an anode substrate; S2. Prepare a perovskite light-absorbing layer on the self-assembled monolayer described in S1; S3. An electron transport layer is prepared on the perovskite light-absorbing layer described in S2; S4. A hole blocking layer and a cathode electrode are sequentially fabricated on the electron transport layer described in S3 to obtain the perovskite photovoltaic device based on a self-assembled monolayer.

3. The preparation method according to claim 2, characterized in that, In step S1, the self-assembled monomolecular solution is spin-coated onto the anode substrate and annealed to obtain the self-assembled monomolecular layer.

4. The preparation method according to claim 3, characterized in that, The method for preparing the self-assembled monomolecular solution is as follows: dissolve the material of the self-assembled monolayer in an organic solvent to obtain the self-assembled monomolecular solution.

5. The preparation method according to claim 3 or 4, characterized in that, The concentration of the self-assembled monomolecular solution is 0.3-1.0 mg / mL.

6. The preparation method according to claim 3, characterized in that, The spin coating speed is 3000-4000 rpm, and the spin coating time is 20-40 s.

7. The preparation method according to claim 3, characterized in that, The annealing temperature is 100-110 ℃.

8. The preparation method according to claim 2, characterized in that, In step S3, an electron transport layer is prepared by spin coating at a rotation speed of 2000-3000 rpm.

Images