Perovskite thin film, preparation method thereof and perovskite solar cell device

Abstract

The invention discloses a perovskite thin film, a preparation method thereof and a perovskite solar cell device, the perovskite thin film comprises a conductive substrate, a hole transport layer and a perovskite layer which are stacked in sequence, the hole transport layer is composed of a first SAM layer and a second SAM layer which are stacked, the first SAM layer is arranged on the conductive substrate, and the second SAM layer is arranged on the conductive substrate. The second SAM layer is arranged between the first SAM layer and the perovskite layer, the first SAM layer can provide first functional groups forming chemical bonds with the conductive substrate, and the second SAM layer can provide second functional groups forming electrostatic interaction, hydrogen bonds or coordinate bonds with lead ions or halogen ions in the perovskite layer. And a pi-pi stacking effect or hydrogen bond interaction force exists between the first SAM layer and the second SAM layer. According to the invention, the problems of energy level mismatch and high open voltage loss in a perovskite solar cell device can be solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite batteries, and particularly relates to a perovskite thin film, a preparation method thereof, and a perovskite solar cell device. BACKGROUND

[0002] As one of renewable energy sources, solar photovoltaic technology has become a key technology for the global response to energy shortage and climate change. In order to further improve the photoelectric conversion efficiency (PCE) of photovoltaic devices, the development of new high-performance photovoltaic materials has become a research hotspot. Perovskite solar cells (PSCs) have shown great potential from the laboratory to industrialization in the past decade due to their excellent light absorption characteristics, long carrier diffusion length, and adjustable bandgap structure.

[0003] At present, the PCE of single-junction PSCs has broken through 27%, close to the single-junction Shockley-Queisser theoretical limit. However, to further improve the device efficiency, perovskite / silicon or perovskite / perovskite tandem solar cells (TSCs) are considered as one of the most promising technical routes. The wide-bandgap perovskite device as the top cell of the tandem cell can widen the light absorption range, achieve higher V OC and better current matching, thereby further breaking through the device efficiency limit. However, the wide-bandgap perovskite device often has a high bulk defect density in the actual preparation process, which leads to increased non-radiative recombination, energy level mismatch, and seriously limits the photoelectric performance and long-term stability of the device. Since the self-assembled monolayer (SAM) exhibits more excellent interface passivation and energy level alignment capabilities, the self-assembled monolayer can be used as a hole transport layer in the wide-bandgap perovskite device, but the wide-bandgap perovskite device still has problems such as energy level mismatch and high open voltage loss.

[0004] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art that is already known in this field. SUMMARY

[0005] The purpose of the present application is to provide a perovskite thin film, a preparation method thereof, and a perovskite solar cell device, which can improve the problems of energy level mismatch and high open voltage loss in the perovskite solar cell device.

[0006] In order to achieve the above object, a specific embodiment of the present application provides a technical solution as follows: a perovskite film, comprising a conductive substrate, a hole transport layer and a perovskite layer which are sequentially stacked, the hole transport layer is composed of a first SAM layer and a second SAM layer which are stacked, the first SAM layer is arranged on the conductive substrate, the second SAM layer is arranged between the first SAM layer and the perovskite layer, the first SAM layer can provide a first functional group which forms a chemical bond with the conductive substrate, the second SAM layer can provide a second functional group which forms an electrostatic action or a hydrogen bond or a coordination bond with lead ions or halogen ions in the perovskite layer, and the first SAM layer and the second SAM layer have a π-π stacking effect or a hydrogen bond interaction force.

[0007] In one or more embodiments of the present application, the first functional group is at least one of a phosphonic acid group, a carboxylic acid group, a sulfonic acid group and a boric acid group.

[0008] In one or more embodiments of the present application, the raw material of the first SAM layer includes any one of Me-4PACz, Me-PhpPACz, 4PABCz, DMAcPA, 2PACz, 4PADCB, Br-4PACz, Ph-2PACz, DMAcP, TPA, PPA, MTPA-BA and DCB-BPA.

[0009] In one or more embodiments of the present application, the second functional group is at least one of a carboxyl group, an ether group and an amine group.

[0010] In one or more embodiments of the present application, the raw material of the second SAM layer includes any one of MeO-4PADCB, MeO-4PACz, MeO-2PACz, MPA-CPA, PPAOMe and DC-PA.

[0011] In one or more embodiments of the present application, the conductive substrate is any one of an ITO (indium tin oxide) conductive substrate, an FTO (fluorine-doped tin oxide), PET (polyethylene terephthalate) and PEN (polyethylene naphthalate).

[0012] A specific embodiment of the present application further provides a preparation method of the perovskite film as described above, comprising the following steps:

[0013] providing the conductive substrate;

[0014] forming the hole transport layer on the conductive substrate;

[0015] forming the perovskite layer on the hole transport layer to obtain the perovskite film.

[0016] In one or more embodiments of the present application, the step of forming the hole transport layer on the conductive substrate comprises:

[0017] The first SAM solution and the second SAM solution are configured respectively;

[0018] The first SAM solution is applied to the conductive substrate, and annealing treatment is performed to form the first SAM layer on the conductive substrate;

[0019] The second SAM solution is applied to the first SAM layer, and annealing treatment is performed to form the second SAM layer on the first SAM layer.

[0020] In one or more embodiments of the present application, the step of forming the first SAM layer specifically comprises:

[0021] The first SAM solution is added dropwise to the conductive substrate and spin-coated at a spin speed of 1000-5000 rpm for 5-60 s, and then annealing treatment is performed at a temperature of 50-250 DEG C for 5-60 min;

[0022] The step of forming the second SAM layer specifically comprises:

[0023] The second SAM solution is added dropwise to the first SAM layer and spin-coated at a spin speed of 1000-5000 rpm for 5-60 s, and then annealing treatment is performed at a temperature of 50-250 DEG C for 5-60 min;

[0024] A specific embodiment of the present application also provides a perovskite solar cell device, which comprises the perovskite thin film as above, and a passivation layer, an electron transport layer, a buffer layer and an electrode which are stacked on the perovskite layer.

[0025] Compared with the prior art, the perovskite thin film of the present application forms stable chemical bonding between the first functional group in the first SAM layer and the surface of the conductive substrate, and the second functional group in the second SAM layer interacts with the lead ions or halogen ions in the perovskite layer through electrostatic interaction, hydrogen bonding or coordination bonding, etc., effectively reducing the interface defects and reducing the non-radiative recombination of carriers at the interface, thereby reducing the open-circuit voltage loss. The interaction between the first SAM layer and the second SAM layer can significantly improve the order of molecular arrangement and the synergistic effect of functional division. The first SAM layer and the second SAM layer simultaneously regulate the nucleation and growth process of the perovskite layer, which helps to form larger-sized grains, reduces the number of grain boundaries, improves the film density, and releases the residual stress in the perovskite growth process, further improving the performance of the device. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative effort based on these drawings.

[0027] Figure 1 Structure diagram of a perovskite thin film in an example of the present application;

[0028] Figure 2 Structure diagram of a perovskite solar cell device in an example of the present application;

[0029] Figure 3 X-ray diffraction pattern (XRD) of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0030] Figure 4 Scanning electron microscope image (SEM) of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0031] Figure 5 Atomic force microscope (AFM) image of the buried interface of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0032] Figure 6 Kelvin probe force microscope (KPFM) image of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0033] Figure 7 Grazing incidence wide-angle X-ray scattering (GIWAXS) image and two-dimensional spectrum of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0034] Figure 8a X-ray photoelectron spectroscopy (XPS) of Pb 4f peak of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0035] Figure 8b X-ray photoelectron spectroscopy (XPS) of I 3d peak of the perovskite thin film in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0036] Figure 9 J–V characteristic curve of the perovskite solar cell device in Example 1, Comparative Example 1 and Comparative Example 2 of the present application;

[0037] Figure 10J-V characteristic curves of the perovskite solar cell devices in Example 2 of the present application, Comparative Example 3, and Comparative Example 4;

[0038] Figure 11 J-V characteristic curves of the perovskite solar cell devices in Example 3 of the present application, Comparative Example 5, and Comparative Example 6.

[0039] Main reference numeral explanation:

[0040] 1, perovskite thin film; 11, conductive substrate; 12, hole transport layer; 121, first SAM layer; 122, second SAM layer; 13, perovskite layer; 2, passivation layer; 3, electron transport layer; 4, buffer layer; 5, electrode. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the present disclosure, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present disclosure.

[0042] As described in the background, in view of the problems of high bulk defect density, high open voltage loss, and single-layer SAM molecules prone to aggregation and single function of the wide-bandgap perovskite solar cell device, the prior art adopts the in-situ molecular compensation and interface modification strategy of mixed SAM molecule solution.

[0043] For example, two kinds of SAM molecules containing phosphonic acid groups and nitrogen / oxygen-containing coordination groups are introduced into the same solution, and the defect passivation of the perovskite surface interface is realized through synergistic self-assembly, so as to reduce non-radiative recombination. That is, there are two kinds of SAM molecules in the single-layer SAM. Or small molecules or ligands, such as oxygen-, nitrogen-, or sulfur-containing Lewis base / acid molecules, are introduced into the perovskite precursor solution, so that they coordinate with Pb 2+ in the perovskite during crystallization, thereby passivating defects.

[0044] However, mixed single-layer SAM requires multiple functional groups to coexist in the same solution, and steric hindrance between molecules is prone to occur, the arrangement is not uniform, and local aggregation is prone to occur, which affects the stability and consistency of interface modification. The single-layer or mixed single-layer SAM has weak control ability on the grain size, orientation, and residual stress release of the perovskite thin film, and it is difficult to effectively reduce the grain boundary defect density. The in-situ molecular compensation strategy has limited ability to regulate the bottom interface energy level, and the compensation molecules mostly act on the inside of the grain, and cannot effectively improve the energy level matching and hole transport efficiency of the hole transport layer (HTL) / perovskite bottom interface.

[0045] The wide band gap perovskite device is one of perovskite solar cell devices.

[0046] To solve the above problems, as shown in the peroviskite thin film 1 in an example of the present application, a conductive substrate 11, a hole transport layer 12, and a peroviskite layer 13 are sequentially stacked. Figure 1 The first SAM layer 121 can provide a first functional group that forms a chemical bond with the conductive substrate 11, and the second SAM layer 122 can provide a second functional group that forms an electrostatic interaction, a hydrogen bond, or a coordination bond with lead ions or halogen ions in the peroviskite layer 13.

[0047] The double-layer SAM interface constructed by sequential deposition realizes precise regulation of the energy band structure and synergistic optimization of the interface physics at the molecular scale. The first SAM layer 121 forms a stable chemical bond with the substrate through its terminal anchoring group, inducing the generation of an interface dipole moment and preliminary regulation of the electrode work function. The second functional group in the second SAM layer produces electrostatic, hydrogen bond, or coordination bond interaction with lead ions or halogen ions in the peroviskite layer, effectively reducing interface defects and reducing non-radiative recombination of carriers at the interface, thereby reducing the open-circuit voltage loss. In addition, the second SAM layer 122 produces π-π stacking or hydrogen bond network interaction with the first SAM layer 121 through its functional group, forming a molecular-level ordered stacking structure. This hierarchical assembly mode not only realizes the gradient transition of the energy band structure and reduces the carrier transport barrier, but also significantly suppresses the interface defect state density through the rearrangement of the electron cloud and the hybridization of the molecular orbit, thereby blocking the migration channel of metal ions and significantly enhancing the intrinsic stability of the peroviskite solar cell device while reducing the non-radiative recombination loss.

[0048] Specifically, the π-π stacking or hydrogen bond interaction between the first SAM layer 121 and the second SAM layer 122 can be understood as the combination of the first SAM layer and the second SAM layer through π-π stacking or hydrogen bond interaction, or the π-π stacking or hydrogen bond interaction between the molecules of the first SAM layer and the molecules of the second SAM layer.

[0049] Specifically, the first functional group is at least one of a phosphonic acid group, a carboxylic acid group, a sulfonic acid group, and a boronic acid group.

[0050] In particular, the first SAM molecule of the first SAM layer 121 is any one of Me-4PACz ([4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid), Me-PhpPACz ([4-(3,6-dimethyl-7H-carbazol-9-yl)phenyl]phosphonic acid), 4PABCz ([2-(9H-9'-phenyl-3,3'-bicarbazol-9-yl)butyl]phosphonic acid), DMAcPA ([4-(2,7-dibromo-9,9-dimethylindolium-10(9H)-yl)butyl]phosphonic acid), 2PACz ((2-(9H-carbazol-9-yl)ethyl)phosphonic acid), 4PADCB ([4-(7H-dibenzo-carbazol-7-yl)butyl]phosphonic acid), Br-4PACz ([4-(3,6-dibromo-9H-carbazol-9-yl)butyl]phosphonic acid), Ph-2PACz ([2-(7H-dibenzo-carbazol-7-yl)ethyl]phosphonic acid), DMAcPA ([4-(2,7-dibromo-9,9-dimethylindolium-10(9H)-yl)butyl]phosphonic acid), TPA ((4,4"-bis(diphenylamino)-1,1':3',1"-terphenyl-5'-carboxylic acid)), PPA ((7-(4-(diphenylamino)phenyl)benzo[C][1,2,5]thiadiazol-4-yl)phosphonic acid), MTPA-BA ((4-(di-p-tolylamino)phenyl)boronic acid), DCB-BPA ([4-(5,9-dibromo-7H-dibenzo-carbazol-7-yl)butyl]phosphonic acid).

[0051] The first SAM layer 121 is a SAM layer formed by self-assembly of the first SAM molecule.

[0052] The second functional group is at least one of a carboxyl group, an ether group, and an amine group.

[0053] In particular, the second SAM molecule of the second SAM layer 122 is any one of MeO-4PADCB ((4-(3,11-dimethoxy-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid), MeO-4PACz ([4-(3,6-dimethoxy-9H-carbazol-9-yl)butyl]phosphonic acid), MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid), MPA-CPA ((2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid), PPAOMe (7-(4-(bis(4-methoxyphenyl)amino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)phosphonic acid), DC-PA ((2,7-dimethoxy-9H-carbazol-9-yl)methyl)phosphonic acid).

[0054] The second SAM layer 122 is a SAM layer formed by self-assembly of the second SAM molecules.

[0055] Specifically, the conductive substrate 11 includes, but is not limited to, any one of ITO (indium tin oxide) conductive substrate, FTO (fluorine-doped tin oxide), PET (polyethylene terephthalate), and PEN (polyethylene naphthalate). The ITO conductive substrate can be an ITO glass substrate commonly used in the prior art.

[0056] The perovskite layer 13 is a structure commonly used in perovskite batteries on the market, and is mainly composed of an organic metal halide semiconductor material with an ABX3 structure, wherein A is usually an organic component such as cesium (Cs) or methylamine (CH3NH2), B is a metal element such as lead (Pb) or tin (Sn), and X is a halogen ion such as chlorine (Cl), bromine (Br), or iodine (I). For example, CH3NH3PbI3 is the most commonly used perovskite material in the photovoltaic field.

[0057] The present application also provides a preparation method of the perovskite thin film, comprising the following steps:

[0058] S1, providing a conductive substrate.

[0059] Specifically, the step S1 is to clean the patterned ITO glass to remove surface impurities such as oil stains, obtain a clean patterned ITO glass substrate, and perform ultraviolet ozone treatment.

[0060] S2, forming a hole transport layer on the conductive substrate.

[0061] Specifically, the step S2 includes: respectively configuring a first SAM solution and a second SAM solution. The first SAM solution is applied to the conductive substrate, and annealing treatment is performed to form a first SAM layer on the conductive substrate. The second SAM solution is applied to the first SAM layer, and annealing treatment is performed to form a second SAM layer on the first SAM layer.

[0062] The steps of respectively configuring the first SAM solution and the second SAM solution are as follows: the concentration of the first SAM molecules (such as Me-4PACz) in the first SAM solution can be 0.1-1 mg / mL, and ultrasonic treatment is performed for 5-30 min to make the first SAM molecules uniformly distributed; the concentration of the second SAM molecules (such as MeO-4PADCB) in the second SAM solution can be 0.1-1 mg / mL, and ultrasonic treatment is performed for 5-30 min to make the second SAM molecules uniformly distributed.

[0063] The step of forming the first SAM layer specifically includes:

[0064] S3、. The first SAM solution is dropped onto the conductive substrate and spin-coated at a speed of 1000-5000 rpm for 5-60 s, and then annealed at a temperature of 50-250 DEG C for 5-60 min.

[0065] Specifically, 20-100 muL of the first SAM solution is dropped onto the ITO glass substrate and spin-coated at a speed of 1000-5000 rpm for 5-60 s under a nitrogen atmosphere. After spin-coating, the sample is annealed on a heating stage at a temperature of 50-250 DEG C for 5-60 min.

[0066] The step of forming the second SAM layer specifically includes:

[0067] The second SAM solution is dropped onto the first SAM layer and spin-coated at a speed of 1000-5000 rpm for 5-60 s, and then annealed at a temperature of 50-250 DEG C for 5-60 min.

[0068] Specifically, 20-100 muL of the second SAM solution is dropped onto the first SAM layer and spin-coated at a speed of 1000-5000 rpm for 5-60 s under a nitrogen atmosphere. After spin-coating, the sample is annealed on a heating stage at a temperature of 50-250 DEG C for 5-60 min.

[0069] S3、. The perovskite layer is formed on the hole transport layer to obtain a perovskite film.

[0070] The concentration of the perovskite solution is 0.1-1.5 mol / L, 20-100 muL of the perovskite solution is spin-coated on the second SAM layer and dropped with an anti-solvent to extract, and a stable phase perovskite film is obtained after annealing on a heating stage. The spin-coating speed is 1000-5000 rpm, the time is 5-60 s, the annealing temperature is 50-250 DEG C, and the annealing time is 5-120 min. The anti-solvent includes but is not limited to chlorobenzene, ethyl acetate, etc.

[0071] The preparation method of the perovskite film has the advantages of simple preparation process and suitability for large-area application. That is, the perovskite film is prepared by a conventional low-temperature solution spin-coating-annealing process, and can be prepared at low temperature and in air. The process flow is simple, has good repeatability and scalability, and is suitable for the large-scale preparation of subsequent stacked perovskite / silicon cells and flexible photovoltaic devices.

[0072] As Figure 2As shown, the present application also provides a perovskite solar cell device, which comprises the perovskite thin film 1 as above, and a passivation layer 2, an electron transport layer 3, a buffer layer 4 and an electrode 5 which are stacked on the perovskite layer.

[0073] The passivation layer 2, the electron transport layer 3, the buffer layer 4 (which can also be referred to as a hole blocking layer) and the electrode 5 can all be of the materials and structures commonly used in the prior art. For example, the material of the passivation layer 2 can be PEAI (phenethylammonium iodide), the material of the electron transport layer 3 can be PCBM ([6,6]-phenyl-C61-butyric acid methyl ester), the material of the buffer layer 4 can be BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), and the electrode 5 can be a common metal electrode (including but not limited to electrodes of materials such as Ag, Au, Cu, Al, etc.).

[0074] The perovskite thin film, its preparation method and the perovskite solar cell device of the present application will be described in detail below with reference to specific examples and comparative examples.

[0075] Example 1

[0076] Preparation of SAM solution: 0.3 mg of Me-4PACz and MeO-4PADCB powders were respectively weighed into two 4 mL glass bottles, 1 mL of anhydrous ethanol was respectively taken by a 1 mL range pipette for dissolution, and ultrasonic treatment was performed for 20 min, to respectively prepare a first SAM solution (Me-4PACz) and a second SAM solution (MeO-4PADCB) with a concentration of 0.3 mg / mL.

[0077] Preparation of perovskite solution: 62.4 mg of CsI, 264.2 mg of PbBr2, 221.3 mg of PbI2 and 165.1 mg of FAI were sequentially weighed into a 5 mL glass bottle, 1 mL of DMF:DMSO=4:1 solution was taken by a 1 mL range pipette for dissolution, and a stirring magnet was added for heating and stirring for 2 h.

[0078] Subsequently, a 1.5 mg / mL PEAI solution (solvent isopropyl alcohol), a 20 mg / mL PCBM solution (solvent chlorobenzene) and a 0.5 mg / mL BCP solution (solvent isopropyl alcohol) were sequentially prepared.

[0079] The patterned ITO glass was cleaned to remove surface impurities such as oil stains, to obtain a clean patterned ITO glass substrate, and was subjected to ultraviolet ozone treatment for 15 min.

[0080] The treated ITO was transferred into a glove box, the ITO glass was fixed on the chuck of a spin coater, 70 μL of Me-4PACz was spin-coated on the surface of the ITO glass substrate at a speed of 4000 rpm, an acceleration of 2000 rpm and a time of 30 s, and was annealed on a 100°C hot plate for 10 min, and after cooling to room temperature, a first SAM layer was obtained. 70 μL of MeO-4PADCB was spin-coated on the surface of the first SAM layer at a speed of 4000 rpm, an acceleration of 2000 rpm and a time of 30 s, and was annealed on a 100°C hot plate for 10 min, and after cooling to room temperature, a second SAM layer, i.e. a hole transport layer, was obtained.

[0081] The perovskite solution after heating and stirring was filtered, 70 μL of the perovskite solution was added dropwise on the hole transport layer, spin-coated using a process of 4000 rpm, 2000 rpm, 40 s, and 160 μL of chlorobenzene (anti-solvent) was added dropwise for extraction at a speed of 4000 rpm, an acceleration of 2000 rpm and a time of 8 s, and was annealed on a 100°C hot plate for 15 min to obtain a perovskite thin film.

[0082] 70 μL of PEAI solution was spin-coated on the perovskite thin film using a process of 4000 rpm / 2000 rpm / 30 s, and was annealed for 10 min to form a passivation layer.

[0083] 60 μL of PCBM solution was spin-coated on the passivation layer using a process of 2000 rpm / 1000 rpm / 30 s, and was annealed for 10 min to form an electron transport layer.

[0084] 80 μL of BCP solution was spin-coated on the electron transport layer using a process of 4000 rpm / 2000 rpm / 30 s, and was annealed for 10 min to form a buffer layer.

[0085] Subsequently, an Ag metal electrode was evaporated on the surface of the buffer layer using a coating machine to obtain the perovskite solar cell device of the present application.

[0086] Example 2

[0087] The SAM solutions were prepared: MeO-2PACz ((2-methoxy-5- (3- (6-phenylcarbazole-9-yl) propyl) benzaldehyde) and 4PADCB (4- (7H- dibenzo (c, g) carbazole-7-yl) butyl) phosphonic acid) were each weighed at 0.3 mg into two 4 mL glass bottles, 1 mL of anhydrous ethanol was taken using a 1 mL range pipette, dissolved and ultrasonically treated for 20 min, and a first SAM solution (MeO-2PACz) and a second SAM solution (4PADCB) were each prepared at a concentration of 0.3 mg / mL.

[0088] Preparation of perovskite solution: 62.4 mg of CsI, 264.2 mg of PbBr2, 221.3 mg of PbI2, and 165.1 mg of FAI were weighed into a 5 mL glass bottle in sequence, and 1 mL of DMF:DMSO=4:1 solution was used to dissolve the above-mentioned substances by using a pipette with a range of 1 mL. A stirring magnet was added for heating and stirring for 2 h.

[0089] Subsequently, 1.5 mg / mL PEAI solution (solvent isopropyl alcohol), 20 mg / mL PCBM solution (solvent chlorobenzene), and 0.5 mg / mL BCP solution (solvent isopropyl alcohol) were prepared in sequence.

[0090] The patterned ITO glass was cleaned to remove impurities such as surface oil, and a clean patterned ITO glass substrate was obtained, and was subjected to ultraviolet ozone treatment for 15 min.

[0091] The treated ITO was transferred to a glove box, and the ITO glass was fixed on the chuck of a spin coater. 70 μL of MeO-2PACz was spin-coated on the surface of the ITO glass substrate at a speed of 4000 rpm, an acceleration of 2000 rpm, and a time of 30 s, and was annealed on a 100°C heating stage for 10 min. After cooling to room temperature, a first SAM layer was obtained. 70 μL of 4PADCB was spin-coated on the surface of the first SAM layer at a speed of 4000 rpm, an acceleration of 2000 rpm, and a time of 30 s, and was annealed on a 100°C heating stage for 10 min. After cooling to room temperature, a second SAM layer was obtained, and finally a hole transport layer was obtained.

[0092] The perovskite solution after heating and stirring was filtered, and 70 μL of the perovskite solution was added dropwise on the hole transport layer. The spin-coating was performed at a speed of 4000 rpm, an acceleration of 2000 rpm, a time of 40 s, and the remaining 8 s was used to add dropwise 160 μL of chlorobenzene (anti-solvent) for extraction, and was annealed on a 100°C heating stage for 15 min to obtain a perovskite thin film.

[0093] 70 μL of PEAI solution was spin-coated on the perovskite thin film by using a process of 4000 rpm / 2000 rpm / 30 s, and was annealed for 10 min to form a passivation layer.

[0094] 60 μL of PCBM solution was spin-coated on the passivation layer by using a process of 2000 rpm / 1000 rpm / 30 s, and was annealed for 10 min to form an electron transport layer.

[0095] 80 μL of BCP solution was spin-coated on the electron transport layer by using a process of 4000 rpm / 2000 rpm / 30 s, and was annealed for 10 min to form a buffer layer.

[0096] Subsequently, a coating machine is used to evaporate Ag metal electrode on the surface of the buffer layer to obtain the perovskite solar cell device.

[0097] Example 3

[0098] The SAM solution is prepared: 2PACz ([2-(9H-carbazol-9-yl)ethyl] phosphonic acid) and MPA-CPA ((2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl) phosphonic acid) are weighed into two 4 mL glass bottles respectively, 1 mL of anhydrous ethanol is taken by a pipette with a range of 1 mL, and ultrasonic treatment is performed for 20 min to prepare a first SAM solution (2PACz) and a second SAM solution (MPA-CPA) with a concentration of 0.3 mg / mL respectively.

[0099] The perovskite solution is prepared: 62.4 mg of CsI, 264.2 mg of PbBr2, 221.3 mg of PbI2, and 165.1 mg of FAI are sequentially weighed into a 5 mL glass bottle, 1 mL of DMF:DMSO=4:1 solution is taken by a pipette with a range of 1 mL, and heating and stirring are performed for 2 h.

[0100] Subsequently, a 1.5 mg / mL PEAI solution (solvent isopropyl alcohol), a 20 mg / mL PCBM solution (solvent chlorobenzene), and a 0.5 mg / mL BCP solution (solvent isopropyl alcohol) are sequentially prepared.

[0101] The patterned ITO glass is cleaned to remove surface impurities such as oil stains, and a clean patterned ITO glass substrate is obtained, and ultraviolet ozone treatment is performed for 15 min.

[0102] The treated ITO is transferred to a glove box, the ITO glass is fixed on the chuck of a spin coater, 70 μL of 2PACz is spin-coated on the surface of the ITO glass substrate at a speed of 4000 rpm, an acceleration of 2000 rpm, and a time of 30 s, and annealing is performed on a 100°C heating stage for 10 min, and after cooling to room temperature, a first SAM layer is obtained. 70 μL of MPA-CPA is spin-coated on the surface of the first SAM layer at a speed of 4000 rpm, an acceleration of 2000 rpm, and a time of 30 s, and annealing is performed on a 100°C heating stage for 10 min, and after cooling to room temperature, a second SAM layer is obtained, and finally a hole transport layer is obtained.

[0103] The perovskite solution after heating and stirring is filtered, 70 μL of the perovskite solution is added dropwise on the hole transport layer, spin coating is performed at a speed of 4000 rpm, an acceleration of 2000 rpm, a time of 40 s, and the remaining 8 s is added dropwise with 160 μL of chlorobenzene (anti-solvent) extraction, and annealing is performed on a 100°C heating stage for 15 min to obtain a perovskite thin film.

[0104] A passivation layer is formed on the perovskite film by spin-coating 70 μL of PEAI solution using a process of 4000 rpm / 2000 rpm / 30 s, annealing for 10 min.

[0105] An electron transport layer is formed on the passivation layer by spin-coating 60 μL of PCBM solution using a process of 2000 rpm / 1000 rpm / 30 s, annealing for 10 min.

[0106] A buffer layer is formed on the electron transport layer by spin-coating 80 μL of BCP solution using a process of 4000 rpm / 2000 rpm / 30 s, annealing for 10 min.

[0107] Subsequently, an Ag metal electrode is evaporated on the surface of the buffer layer by a coating machine to obtain the perovskite solar cell device of the present application.

[0108] Comparative Example 1

[0109] The hole transport layer only includes the first SAM layer without the second SAM layer, which is basically consistent with Example 1.

[0110] Comparative Example 2

[0111] The hole transport layer only includes the second SAM layer without the first SAM layer, which is basically consistent with Example 1.

[0112] Comparative Example 3

[0113] The hole transport layer only includes the first SAM layer without the second SAM layer, which is basically consistent with Example 2.

[0114] Comparative Example 4

[0115] The hole transport layer only includes the second SAM layer without the first SAM layer, which is basically consistent with Example 2.

[0116] Comparative Example 5

[0117] The hole transport layer only includes the first SAM layer without the second SAM layer, which is basically consistent with Example 3.

[0118] Comparative Example 6

[0119] The hole transport layer only includes the second SAM layer without the first SAM layer, which is basically consistent with Example 3.

[0120] Comparative Example 7

[0121] The hole transport layer further comprises a third SAM layer disposed between the first SAM layer and the second SAM layer, and the third SAM molecules of the third SAM layer are Me-PhpPACz ([4-(3,6-dimethyl-7H-carbazol-9-yl)phenyl]phosphonic acid).

[0122] Figure 3 X-ray diffraction patterns (XRD) of the perovskite films in Example 1, Comparative Example 1 and Comparative Example 2 were obtained. The XRD patterns were obtained by Figure 3 It can be seen that the crystallinity of the perovskite film in Example 1 is enhanced, which indicates that the hole transport layer of the present application helps to promote the ordered growth of perovskite crystals and reduce internal defects, thereby improving the crystalline quality of the film.

[0123] Figure 4 Scanning electron microscope images (SEM) of the perovskite films in Example 1, Comparative Example 1 and Comparative Example 2 were obtained. The SEM images were obtained by Figure 4 It can be seen that the grain size of the perovskite film in Example 1 is significantly increased and the grain boundaries are reduced, which indicates that the hole transport layer of the present application can effectively regulate the nucleation and grain growth process of the perovskite layer, and help to passivate the grain boundaries and surface defects.

[0124] Figure 5 Atomic force microscope (AFM) images of the buried interface of the perovskite films in Example 1, Comparative Example 1 and Comparative Example 2 were obtained. Figure 6 Kelvin probe force microscope (KPFM) images of the perovskite films in Example 1, Comparative Example 1 and Comparative Example 2 were obtained. The KPFM images were obtained by Figure 5 and Figure 6 It can be seen that the perovskite film in Example 1 has lower roughness and more uniform surface potential distribution.

[0125] Figure 7 Grazing incidence wide-angle X-ray scattering (GIWAXS) images and two-dimensional spectra of the perovskite films in Example 1, Comparative Example 1 and Comparative Example 2 were obtained. According to Figure 7 It can be seen that there is almost no obvious peak shift under the characteristic diffraction peak of the perovskite film in Example 1, which indicates that the hole transport layer of the present application can effectively relieve the residual stress in the film and stabilize the lattice structure.

[0126] Figure 8a and Figure 8b X-ray photoelectron spectroscopy (XPS) of the perovskite film in Example 1, it can be observed that the binding energy of Pb 4f and I 3d energy levels in the perovskite film is slightly shifted compared with the control group, which indicates that the hole transport layer in Example 1 interacts with the perovskite.

[0127] Figure 9The J-V characteristic curves of the perovskite solar cell devices in Example 1, Comparative Example 1 and Comparative Example 2 were measured according to the following method. Figure 9 It can be seen that the perovskite solar cell device in Example 1 is superior to the perovskite solar cell devices in Comparative Example 1 and Comparative Example 2 in terms of various performance parameters.

[0128] Figure 10 The J-V characteristic curves of the perovskite solar cell devices in Example 2, Comparative Example 3 and Comparative Example 4 were measured according to the following method. Figure 10 It can be seen that the perovskite solar cell device in Example 2 is superior to the perovskite solar cell devices in Comparative Example 3 and Comparative Example 4 in terms of various performance parameters.

[0129] Figure 11 The J-V characteristic curves of the perovskite solar cell devices in Example 3, Comparative Example 5 and Comparative Example 6 were measured according to the following method. Figure 11 It can be seen that the perovskite solar cell device in Example 3 is superior to the perovskite solar cell devices in Comparative Example 5 and Comparative Example 6 in terms of various performance parameters.

[0130] In summary, the perovskite thin film, the preparation method thereof and the perovskite solar cell device of the present application have the following beneficial effects:

[0131] Good multifunctional synergistic regulation effect: compared with single-layer SAM or mixed single-layer SAM, mixing multiple functional groups in the same layer is easy to cause independent crystallization, and the double-layer SAM structure of the present application can significantly improve the order of molecular arrangement and the synergistic effect of functional division.

[0132] Significant reduction in vacancy defect density and inhibition of non-radiative recombination: the second functional group in the second SAM layer forms a coordination effect with Pb²⁺ or halogen vacancies in the perovskite, effectively reducing the interface defects and reducing the non-radiative recombination of carriers at the interface, thereby reducing the open-circuit voltage loss.

[0133] Regulation of crystallization behavior and release of residual stress: the double-layer SAM structure of the present application simultaneously regulates the nucleation and growth process of the perovskite layer, which helps to form larger-sized grains, reduces the number of grain boundaries, improves the film density, and releases the residual stress during the growth of the perovskite, further improving the performance of the device.

[0134] Simple preparation process, suitable for large-area application: the present application uses a conventional low-temperature solution spin-coating-annealing process, which can be prepared under low-temperature and air conditions, has a simple process flow, good repeatability and scalability, and is suitable for the large-scale preparation of subsequent stacked perovskite / silicon cells and flexible photovoltaic devices.

[0135] It will be apparent to those skilled in the art that the disclosure is not limited to the details of the above-exemplified embodiments and that the disclosure can be implemented in other particular forms without departing from the spirit or essential characteristics of the disclosure. The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the disclosure being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No feature of the claims is to be construed as limiting the claims to the exact nature of the features described therein.

[0136] Furthermore, it should be understood that although the description is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A perovskite thin film, characterized in that, The device comprises a conductive substrate, a hole transport layer, and a perovskite layer stacked sequentially. The hole transport layer consists of a first SAM layer and a second SAM layer stacked together. The first SAM layer is disposed on the conductive substrate, and the second SAM layer is disposed between the first SAM layer and the perovskite layer. The first SAM layer can provide a first functional group that forms a chemical bond with the conductive substrate, and the second SAM layer can provide a second functional group that forms an electrostatic interaction, a hydrogen bond, or a coordination bond with lead ions or halide ions in the perovskite layer. The first SAM layer and the second SAM layer have a π-π stacking effect or a hydrogen bond interaction force.

2. The perovskite thin film according to claim 1, characterized in that, The first functional group is at least one of phosphonic acid group, carboxylic acid group, sulfonic acid group and boric acid group.

3. The perovskite thin film according to claim 1, characterized in that, The first SAM molecule of the first SAM layer is any one of Me-4PACz, Me-PhpPACz, 4PABCz, DMAcPA, 2PACz, 4PADCB, Br-4PACz, Ph-2PACz, DMAcP, TPA, PPA, MTPA-BA, and DCB-BPA.

4. The perovskite thin film according to claim 1, characterized in that, The second functional group is at least one of a carboxyl group, an ether group, and an amino group.

5. The perovskite thin film according to claim 1, characterized in that, The second SAM molecule in the second SAM layer is any one of MeO-4PADCB, MeO-4PACz, MeO-2PACz, MPA-CPA, PPAOMe, and DC-PA.

6. The perovskite thin film according to claim 1, characterized in that, The conductive substrate is any one of ITO, FTO, PET, and PEN.

7. A method for preparing a perovskite thin film as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Provide a conductive substrate as described above; The hole transport layer is formed on the conductive substrate; The perovskite layer is formed on the hole transport layer to obtain the perovskite thin film.

8. The method for preparing perovskite thin films according to claim 7, characterized in that, The step of forming the hole transport layer on the conductive substrate includes: Prepare the first SAM solution and the second SAM solution respectively; The first SAM solution is applied to the conductive substrate and then annealed to form the first SAM layer on the conductive substrate. The second SAM solution is applied onto the first SAM layer and then annealed to form the second SAM layer on the first SAM layer.

9. The method for preparing perovskite thin films according to claim 8, characterized in that, The steps for forming the first SAM layer specifically include: The first SAM solution was dropped onto the conductive substrate and spin-coated. The spin-coating speed range was 1000~5000 rpm and the spin-coating time was 5~60 s. After spin-coating, annealing was performed at a temperature of 50~250℃ for 5~60 min. The steps for forming the second SAM layer specifically include: The second SAM solution was dropped onto the first SAM layer and spin-coated. The spin-coating speed range was 1000~5000 rpm and the spin-coating time was 5~60s. After spin-coating, annealing was performed at a temperature of 50~250℃ for 5~60min.

10. A perovskite solar cell device, characterized in that, It includes the perovskite thin film as described in any one of claims 1 to 6, and a passivation layer, an electron transport layer, a buffer layer, and an electrode stacked on the perovskite layer.

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