Perovskite photovoltaic device based on self-assembled monomolecular layer and preparation method thereof

Abstract

The invention discloses a perovskite photovoltaic device based on a self-assembled monomolecular layer and a preparation method of the perovskite photovoltaic device. The perovskite photovoltaic device comprises an anode substrate, and the self-assembled monomolecular layer, a perovskite light absorption layer, an electron transport layer, a hole blocking layer and a cathode electrode which are sequentially arranged on one side of the anode substrate, the material of the self-assembled monomolecular layer contains a methylthio substituent group, a carbazole element is used as a parent nucleus, and a phosphonic acid element is used as an anchoring group. The invention provides a novel method for molecular design of the SAM material, and provides a highly universal functional substituent group. The MeS-CbzPh-based perovskite photovoltaic device prepared by the invention realizes the energy conversion efficiency of 26.01%, maintains the efficiency of 93.3% after maximum power point tracking of continuous operation for 1000 hours, and shows excellent stability.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite photovoltaic devices, and in particular to a perovskite photovoltaic device based on a self-assembled monomolecular layer and a preparation method thereof. Background Art

[0002] Perovskite solar cells (PSCs) are divided into two categories: upright devices (nip) and inverted devices (pin). Inverted PSCs have attracted widespread attention due to their lower processing temperature and good compatibility with flexible and stacked solar cells. The power conversion efficiency (PCE) of inverted PSCs has made significant progress due to the development and use of self-assembled monolayers (SAMs) as hole transport layers. This is because SAMs provide tunable energy levels, can passivate defects at the buried interface of perovskites, and have low synthesis costs. Methoxy (MeO-) groups are usually introduced into high-performance SAM materials, 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 the SAM and the perovskite layer, but also passivates defects at the buried interface, thereby improving the performance of the device. However, due to the strong electron donor ability of the methoxy group, the highest occupied molecular orbital (HOMO) of the SAM material becomes significantly shallower, resulting in a mismatch with the HOMO energy level of the perovskite layer. Therefore, finding an alternative group that can retain all the advantages of the methoxy group and achieve a better match to the HOMO energy level is a key strategy to further improve the performance of inverted PSCs. Summary of the invention

[0003] To solve the above technical problems, the purpose of the present invention is to provide a perovskite photovoltaic device based on a self-assembled monolayer and a preparation method thereof, and to provide a multifunctional substituent, a methylthio (MeS-) substituent group, as a substitute for the traditional methoxy group in the basic SAM material.

[0004] The present invention is achieved through the following technical solutions:

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

[0006]

[0007] Wherein, n is an integer of 0-10, 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 hydrogen at the same time.

[0008] The perovskite photovoltaic device provided by the present invention is an inverted device, and the material of the self-assembled monolayer provided contains a methylthio (MeS-) substituent group, with a carbazole moiety as a parent nucleus and a phosphonic acid moiety as an anchoring group. The inventors found that lead ions are soft acids with large ionic radius and low charge density. Sulfur atoms, as a soft base, have an atomic radius larger than that of oxygen atoms and low electronegativity, so the outermost electrons of sulfur atoms can move more freely toward the soft acid, thereby forming a stronger Pb-S bond. Therefore, the methylthio group can more effectively passivate the buried interface of the perovskite. In addition, due to the weak electron donor ability of the methylthio group, the methylthio-based SAM material exhibits a better HOMO energy level match with the perovskite. The interface between the perovskite and the methylthio-based SAM material achieves more efficient charge transfer and alleviates the problem of reverse charge accumulation. Finally, the present invention significantly improves the efficiency and stability of PSCs.

[0009] Furthermore, the structural formula of the material of the self-assembled monolayer 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 substituent group exhibits high versatility and also exhibits excellent performance in the more common 4PACz series of SAM materials.

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

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

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

[0016] S3. Preparing an electron transport layer on the perovskite light absorbing layer described in S2;

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

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

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

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

[0021]

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

[0023]

[0024] In a specific implementation, 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] Furthermore, in step S1, the self-assembled monomolecular solution is spin-coated on the anode substrate, and the self-assembled monomolecular layer is obtained after annealing.

[0026] Furthermore, the preparation method of the self-assembled monomolecular solution is: dissolving the material of the self-assembled monomolecular layer 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° C., and the annealing time is 10-15 min.

[0030] Furthermore, 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 to obtain a perovskite precursor solution after reaction; and coating the perovskite precursor solution on the self-assembled monolayer.

[0031] Furthermore, the lead bromide is purified.

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

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

[0034] Furthermore, the spin coating has a rotation speed of 4000-6000 rpm, and the anti-solvent is added 20-30 seconds after the start of the spin coating, and the spin coating is continued for 10-20 seconds before annealing at 90-110° C. for 30-60 minutes.

[0035] Further, the anti-solvent comprises chlorobenzene (CB).

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

[0037] Furthermore, in step S3, the material of the electron transport layer includes [6,6]-phenyl C61-butyric acid methyl ester (PCBM).

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

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

[0040] Furthermore, in step S4, the material of the hole blocking layer includes bathocuproine (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 present invention has the following beneficial effects:

[0044] 1. The present invention provides a novel method for the molecular design of SAM materials and provides a highly versatile functional substituent group. The methylthio substituent group is introduced into the SAM material. This group acts as a regulatory bridge, enhances the interaction with the perovskite, and achieves a better band level alignment.

[0045] 2. The inverted perovskite photovoltaic device prepared by the MeS-CbzPh-based SAM material provided by the present invention achieved an optimal PCE of 26.01%. In addition, during maximum power point tracking, the unencapsulated PSCs showed excellent stability, maintaining 93.3% of the initial PCE after 1000 hours of continuous operation of maximum power point tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The chemical structures, electrostatic potential surfaces and binding energy data diagrams of CbzPh, MeO-CbzPh and MeS-CbzPh with perovskite; wherein a is the chemical structure and electrostatic potential surface diagram, and b is the binding energy data diagram.

[0047] Figure 2 PL spectra of the perovskite film in the perovskite photovoltaic device of Example 1 and Comparative Examples 1-2 and DLCP curves of the perovskite photovoltaic device; wherein a is the PL spectrum and b is the DLCP curve.

[0048] Figure 3 It is a graph showing the JV performance test results of the perovskite photovoltaic devices of Example 1 and Comparative Examples 1-2.

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

[0050] Figure 5 It is a stability data diagram of the maximum power point tracking of the perovskite photovoltaic devices of Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

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

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

[0054] The ITO substrate, 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 purchased from Sigma-Aldrich. Dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and isopropyl alcohol (IPA) were purchased from Alfa Aesar Ltd.

[0055] In the following examples and comparative examples, the method for preparing the self-assembled monomolecular solution is as follows: 0.5 mg of the self-assembled monomolecular layer material is dissolved in 1 mL of ethanol, and the self-assembled monomolecular solution is obtained after stirring at room temperature for 7 hours.

[0056] In the following embodiments and comparative examples, the preparation method of the perovskite precursor solution is as follows: 620 mg PbI2, 213 mg FAI, 12.4 mg MABr, 43 mg PbBr2 and 11.7 mg CsI are dissolved in 1 mL of a mixed solvent of DMF and DMSO, wherein the volume ratio of DMF to DMSO is 4:1, and the perovskite precursor solution is obtained after stirring at room temperature for 7 hours.

[0057] In the following examples and comparative examples, the preparation method of the electron transport layer solution is as follows: 20 mg of PCBM is dissolved in 1 mL of chlorobenzene, and the mixture is stirred at room temperature for 7 hours to obtain an electron transport layer precursor solution.

[0058] Example 1

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

[0060] S1. Prepare a 5 nm MeS-CBzPh layer on an ITO substrate: The ITO substrate was ultrasonically cleaned twice with deionized water, acetone, and ethanol respectively, baked for 20 min to completely remove the solvent and moisture, and treated with UV lamp and ozone for 20 min to obtain an ITO substrate; the MeS-CBzPh solution was spin-coated and deposited on the ITO substrate, and 70 μL of MeS-CBzPh solution was statically coated, spin-coated at 3000 rpm for 30 s, and annealed at 100°C for 10 min to obtain a MeS-CBzPh layer.

[0061] S2. Prepare a 500 nm Perovskite layer on the MeS-CBzPh layer described in S1: statically coat 70 μL of perovskite precursor solution on the MeS-CBzPh layer, spin-coat the perovskite precursor solution at 5000 rpm for 25 seconds, then drop 200 μL of chlorobenzene antisolvent and continue spin-coating for 10 seconds. After spin-coating, transfer it to a heating table for annealing at 100°C for 45 minutes to obtain a 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, statically coat 70 μl of PCBM solution, and spin coat at a speed of 2000 rpm for 30 seconds to obtain a 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 ITO / MeS-4PACz / Perovskite / PCBM / BCP / Ag based on MeS-4PACz comprises an ITO substrate, a MeS-4PACz layer, a perovskite light absorbing layer, a PCBM layer, a BCP layer and an Ag electrode which are sequentially arranged on one side of the ITO substrate, and the preparation method is basically the same as that in Example 1.

[0066] Comparative Example 1

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

[0068] Comparative Example 2

[0069] An inverted perovskite photovoltaic device ITO / MeO-CBzPh / Perovskite / PCBM / BCP / Ag based on MeO-CBzPh comprises an ITO substrate, a MeO-CBzPh layer, a perovskite light absorbing layer, a PCBM layer, a BCP layer and an Ag electrode which are sequentially arranged on one side of the ITO substrate, and the preparation method is basically the same as that in Example 1.

[0070] Comparative Example 3

[0071] An inverted perovskite photovoltaic device ITO / 4PACz / Perovskite / PCBM / BCP / Ag based on 4PACz comprises an ITO substrate, a 4PACz layer, a perovskite light absorbing layer, a PCBM layer, a BCP layer and an Ag electrode sequentially arranged on one side of the ITO substrate, and the preparation method is basically the same as that in Example 1.

[0072] Comparative Example 4

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

[0074] Figure 1 The chemical structure, electrostatic potential surface and binding energy data of CbzPh, MeO-CbzPh and MeS-CbzPh with perovskite are shown in Figure 1. A is the chemical structure and electrostatic potential surface, and b is the binding energy data. CbzPh is used as a SAM reference material, which is often used in inverted devices and exhibits excellent performance. Figure 1 As shown in Figure a, the calculated electrostatic potential surface (ESP) of the three molecules shows 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, and 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 PL spectra of the perovskite film in the perovskite photovoltaic device of Example 1 and Comparative Examples 1-2 and the DLCP curve of the perovskite photovoltaic device; wherein a is the PL spectrum and b is the DLCP curve. Figure 2 As shown in the steady-state photoluminescence (PL) spectrum of a, the PL peak position of the perovskite remains unchanged at 808 nm, indicating that the perovskite band gap is 1.53 eV. It is worth noting that the PL intensity of the perovskite film on the MeS-CbzPh substrate is significantly enhanced, which indicates that the non-radiative recombination and defects at the buried interface of the perovskite film are reduced. In order to verify the reduction of the 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 at different bias voltages. Figure 2 (b) shows the driver-level capacitance distribution (DLCP) curve derived from the CV characteristics, and the trap density at the buried interface of the optimized film is significantly reduced compared with the original perovskite film.

[0076] Figure 3 The JV performance test results of the perovskite photovoltaic device of Example 1 and Comparative Examples 1-2 are shown, and the current density-voltage (JV) curve and the corresponding efficiency of the perovskite photovoltaic device are tested. Figure 3 As can be seen from the figure, the device based on CbzPh achieves a PCE of 24.36% and an open circuit voltage (V OC ) is 1.17V, the short-circuit current density (J SC ) is 25.62 mA / cm 2 , the fill factor (FF) is 80.29%. The introduction of substituents in CbzPh significantly improves the performance of the corresponding devices. The device based on MeO-CbzPh shows a PCE of 25.16% and a V OC is 1.18V, J SC 26.34 mA / cm 2 , FF is 80.90%; the device based on MeS-CbzPh shows a PCE of 26.01%, V OC is 1.19V, J SC 26.43 mA / cm 2 , FF is 81.98%. The improvement in 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 of the perovskite photovoltaic devices of Examples 1-2 and Comparative Examples 1-4 are shown in FIG. Figure 4It can be seen that the highest PCE of the device based on MeS-4PACz is 24.12%, which is better than the optimal PCE 20.41% of the device based on 4PACz and the optimal PCE 21.45% of the device based on MeO-4PACz. The improvement of the device performance of the present invention is mainly due to the ability of the methylthio group to adjust the HOMO energy level of the 4PACz molecule and its excellent ability to passivate the interface defects of the buried perovskite. Similarly, the efficiency of the devices based on the CbzPh series also shows a consistent trend. The device based on MeS-CbzPh achieves a maximum efficiency of 26.01%, which exceeds the 24.36% of the device based on CbzPh and the 25.16% of the device based on MeO-CbzPh.

[0078] Figure 5 The maximum power point tracking of the perovskite photovoltaic devices of Example 1 and Comparative Examples 1-2 under one sunlight simulated continuous illumination is shown, and the devices based on MeS-CbzPh show better output stability. The devices based on MeO-CbzPh and MeS-CbzPh maintained 85.5% and 93.3% of their initial PCE after 1000 hours, respectively, while the devices based on CbzPh dropped below 77.8%. This excellent long-term stability indicates that more effective defect passivation is achieved at the perovskite interface by incorporating MeS-groups.

[0079] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A perovskite photovoltaic device based on a self-assembled monolayer, characterized in that: It includes an anode substrate, a self-assembled monolayer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer and a cathode electrode arranged in sequence on one side of the anode substrate, and the structural formula of the material of the self-assembled monolayer is shown in formula (I): Wherein, n is an integer of 0-10, 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 hydrogen at the same time.

2. The perovskite photovoltaic device according to claim 1, characterized in that: The structural formula of the material of the self-assembled monolayer is selected from:

3. A method for preparing a perovskite photovoltaic device based on a self-assembled monolayer according to claim 1 or 2, characterized in that: The following steps are involved: S1. Preparing a self-assembled monolayer on an anode substrate; S2. Preparing a perovskite light absorbing layer on the self-assembled monolayer described in S1; S3. Preparing an electron transport layer on the perovskite light absorbing layer described in S2; S4. A hole blocking layer and a cathode electrode are sequentially prepared on the electron transport layer described in S3 to obtain the perovskite photovoltaic device based on the self-assembled monolayer.

4. The preparation method according to claim 3, characterized in that: In step S1, a self-assembled monomolecular solution is spin-coated on an anode substrate, and the self-assembled monomolecular layer is obtained after annealing.

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

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

7. The preparation method according to claim 4, characterized in that: The rotation speed of the spin coating is 3000-4000 rpm, and the spin coating time is 20-40s.

8. The preparation method according to claim 4, characterized in that: The annealing treatment is carried out at a temperature of 100-110°C.

9. The preparation method according to claim 3, characterized in that: In step S2, the preparation of the perovskite light-absorbing layer includes the following steps: dissolving lead iodide, cesium iodide, formamidine iodine, lead bromide and methylammonium bromide in an organic solvent, and obtaining a perovskite precursor solution after reaction; and coating the perovskite precursor solution on the self-assembled monolayer.

10. The preparation method according to claim 3, characterized in that: In step S3, the electron transport layer is prepared by spin coating, and the rotation speed of the spin coating is 2000-3000 rpm.

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