A hole transport layer containing betaine hydrochloride additive and its inverse wide-bandgap perovskite solar cell

Abstract

This invention relates to the field of solar cell technology, specifically to a hole transport layer containing betaine hydrochloride additive and its inverse wide-bandgap perovskite solar cell. The hole transport layer comprises a nickel oxide layer and a self-assembled molecular layer formed on its surface. The self-assembled molecular layer contains (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride. The introduction of betaine hydrochloride improves the conductivity of the hole transport layer through the interaction of its carboxylic acid groups with nickel oxide, and inhibits its clustering behavior through interaction with the self-assembled molecules, thereby improving film uniformity and effectively passivating buried interface defects in the perovskite light-absorbing layer. The inverse wide-bandgap perovskite solar cell fabricated based on this hole transport layer exhibits significantly improved open-circuit voltage and fill factor, ultimately achieving a photoelectric conversion efficiency exceeding 21.7%. This invention provides an effective interface engineering strategy for fabricating efficient and stable wide-bandgap perovskite solar cells and tandem devices.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a hole transport layer containing betaine hydrochloride additive and its inverse wide-bandgap perovskite solar cell. Background Technology

[0002] Solar energy can be directly obtained in most parts of the Earth, making it particularly suitable for remote areas or distributed power generation scenarios. However, the large-scale application of solar energy faces a core challenge: how to convert sunlight into electricity at low cost and high efficiency. Although traditional silicon-based solar cells have been commercialized, their theoretical efficiency limit (29.4%) and manufacturing cost restrict further development. Therefore, the development of new high-efficiency photovoltaic technologies is imperative. Perovskite solar cells (PSCs) possess enormous commercial potential due to their cost-effectiveness, ease of fabrication, and tunable bandgap. However, the theoretical efficiency limit of a single-junction solar cell is 33%. To overcome this limitation, all-perovskite tandem solar cells have emerged. By vertically stacking perovskite materials with different bandgapes, they achieve absorption over a wider range of the solar spectrum, thus breaking through the efficiency limit of single-junction solar cells.

[0003] To achieve high-efficiency all-perovskite tandem solar cells, fabricating high-performance wide-bandgap top-mounted cells is crucial. These tandem cells often employ an inverted (pin) structure, where the bottom hole transport layer (HTL) is critical to device performance. It is responsible not only for hole extraction and transport but also directly affects the crystallinity and interface properties of the upper perovskite film. Therefore, developing effective optimization strategies for the hole transport layer in wide-bandgap solar cells is extremely necessary. Nickel oxide (NiO) x Due to its good stability, high light transmittance, and process compatibility with perovskites, it is often used as a hole transport material. However, the large energy level mismatch between it and wide-bandgap perovskites severely limits device efficiency. Therefore, NiO is often used... x A self-assembled monolayer (SAM) bilayer HTL structure. This structure is anchored to NiO through phosphonic acid groups at the ends of the SAM molecules. x The surface can not only improve energy level alignment and enhance device stability, but also serve as a template for perovskite growth.

[0004] However, this double-layer structure still has several problems: First, NiO... x The conductivity of NiO is typically low; its conductivity mainly originates from holes formed by nickel vacancies or interstitial oxygen, which act as majority carriers in NiO. x In the crystal lattice of Ni, there are usually a certain amount of nickel vacancies. In order to maintain electroneutrality, a portion of the Ni in the lattice... 2+It will lose an electron and transform into Ni. 3+ These Ni 3+ This can be seen as a site where an electron has been "captured," which is different from the normal Ni. 2+ Ni 3+ It's like having a positively charged center (hole). Electrons can jump between different energy levels of nickel ions, which macroscopically manifests as the movement of holes, thus generating conductivity; therefore, Ni 3+ The content of NiO directly determines x The carrier concentration and conductivity of Ni are increased, thus improving Ni 3+ The ratio of NiO x The conductivity is crucial. Secondly, the SAM molecular layers used often exhibit clustering behavior due to the self-aggregation effect of phosphonic acid groups, which leads to the self-assembled molecular layers in NiO... x The uneven surface distribution of NiO severely affects the subsequent deposition of perovskite films. Finally, NiO x The SAM molecular layer, as the HTL layer of a wide-bandgap perovskite, has very limited passivation capability at the buried interface, resulting in many defects remaining at the perovskite buried interface. These problems can lead to NiO... x The low carrier extraction capability of the SAM molecular layer leads to a large amount of non-radiative recombination at the buried interface, which in turn causes severe Vo damage to the wide-bandgap solar cell. oc Losses can affect the efficiency of wide-bandgap solar cells.

[0005] Therefore, there is an urgent need to develop a method that can simultaneously improve NiO x A comprehensive strategy involving improving conductivity, enhancing the uniformity of SAM molecular distribution, and strengthening the passivation of the perovskite buried interface is employed to fabricate high-performance wide-bandgap perovskite solar cells, laying the foundation for high-efficiency all-perovskite tandem devices. Summary of the Invention

[0006] In view of this, the present invention provides a hole transport layer containing betaine hydrochloride additive and its inverse wide-bandgap perovskite solar cell. By adding a certain amount of betaine hydrochloride to a (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (Me-4PACz) precursor solution, the carboxylic acid groups contained on the betaine hydrochloride can react with NiO. x Interaction, thereby improving Ni 3+ with Ni 2+The ratio of betaine hydrochloride to Me-4PACz increases conductivity. Simultaneously, the interaction between betaine hydrochloride and Me-4PACz hinders the self-aggregation effect of phosphonic acid groups, suppressing the clustering behavior of Me-4PACz. Furthermore, betaine hydrochloride effectively passivates the perovskite at the buried interface, resulting in a hole transport layer with better conductivity, more uniform distribution, and suitable energy levels. This leads to a wide-bandgap perovskite solar cell with superior photoelectric performance, solving the problems of excessive open-circuit voltage loss, energy level mismatch with the hole transport layer, and uneven distribution of self-assembled molecular layers in existing wide-bandgap perovskite solar cells.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a hole transport layer for a perovskite solar cell, comprising: a nickel oxide layer; and a self-assembled molecular layer formed on the surface of the nickel oxide layer; The self-assembled molecular layer comprises (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride.

[0008] Preferably, the amount of betaine hydrochloride added is 10% to 20% of the molar amount of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid.

[0009] Specifically, insufficient betaine hydrochloride will not significantly improve the optimization of nickel oxide film surface defects, (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid cluster behavior, and perovskite buried interface, thus failing to achieve optimal efficiency. Excessive betaine hydrochloride will lead to an excessively thick transport layer and will also occupy the positions that (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid should occupy, resulting in a decrease in device current and fill power.

[0010] Preferably, the thickness of the nickel oxide layer is 10-15 nm; the thickness of the self-assembled molecular layer is 1-3 nm.

[0011] In a second aspect, the present invention provides a method for preparing a hole transport layer as described in the first aspect, comprising the following steps: S1-1. Disperse nickel oxide in deionized water and then spin-coat it onto the surface of a transparent conductive substrate to obtain a nickel oxide layer. S1-2. Dissolve (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride in ethanol to obtain a mixed solution, and then spin-coat it onto the surface of the nickel oxide layer to obtain a hole transport layer.

[0012] Preferably, in the mixed solution of steps S1-2, the concentration of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid is 0.5 mg / mL; and the concentration of betaine hydrochloride is 0.023~0.046 mg / mL.

[0013] Thirdly, the present invention provides a perovskite solar cell comprising a transparent conductive substrate, a hole transport layer as described in the first aspect, an organic-inorganic hybrid metal halide perovskite light-absorbing layer, a metal fluoride layer, an electron transport layer, a hole blocking layer, and a metal electrode, which are stacked sequentially.

[0014] Preferably, the organic-inorganic hybrid metal halide perovskite light-absorbing layer contains Cs. 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.35 3; the metal fluoride layer is selected from LiF, MgF2 or NaF; the electron transport layer contains a fullerene derivative; the hole blocking layer contains copper bath; the metal electrode is selected from Ag, Cu or Au.

[0015] Preferably, the thickness of the electron transport layer is 25-30 nm; and the thickness of the metal electrode is 80-100 nm.

[0016] Fourthly, the present invention provides a method for preparing a perovskite solar cell as described in the third aspect, comprising the following steps: S1. Provide a transparent conductive substrate and clean it; S2. Prepare a nickel oxide layer on the cleaned substrate; S3. Spin-coat the nickel oxide layer with a mixed solution containing (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride to form a self-assembled molecular layer and obtain a hole transport layer. S4. Spin-coat the perovskite precursor solution onto the hole transport layer, and then perform antisolvent-assisted crystallization and annealing to form a perovskite light-absorbing layer. S5. On the perovskite light-absorbing layer, a metal fluoride layer, an electron transport layer, a hole blocking layer, and a metal electrode are sequentially prepared.

[0017] Preferably, the concentration of the perovskite precursor solution is 0.8~1.25 mmol / mL.

[0018] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention introduces betaine hydrochloride, whose carboxylic acid group reacts with nickel oxide (NiO) in its molecule. x) Specific interactions occur on the surface, effectively regulating Ni 3+ / Ni 2+ The increased ratio of [specific parameters] improves the hole carrier concentration, thereby substantially enhancing the conductivity of the composite hole transport layer and laying the physical foundation for efficient charge extraction.

[0019] (2) In this invention, there is an interaction between betaine hydrochloride and Me-4PACz molecules, which can effectively inhibit the self-aggregation and clustering behavior of phosphonic acid groups, so that the self-assembled monolayer in NiO x A modified layer with better coverage and extremely uniform distribution is formed on the surface. This directly manifests as a significant improvement in the uniformity of interfacial potential and the enhancement of surface wettability. The contact angle of the perovskite precursor solution on it is significantly reduced, creating an ideal substrate for the subsequent preparation of high-quality perovskite thin films.

[0020] (3) In this invention, the carboxyl group and quaternary ammonium group in the betaine hydrochloride molecule can synergistically passivate defect states such as uncoordinated lead ions and halogen vacancies at the bottom of the perovskite layer. This results in a significant reduction in the defect density of the perovskite thin film grown based on the hole transport layer of this invention, effective suppression of nonradiative recombination of charge carriers, and a significant extension of the charge carrier lifetime.

[0021] (4) Thanks to optimized charge extraction, uniform interface contact and enhanced defect passivation, the open-circuit voltage and fill factor of the inverted wide-bandgap perovskite solar cell prepared by the present invention are significantly improved, and the photoelectric conversion efficiency of the driving device is greatly increased, which verifies the effectiveness and superiority of the present technical solution for realizing high-performance perovskite photovoltaic devices. Attached Figure Description

[0022] Figure 1 Comparative Example 1 (NiO) x / Me-4PACz) and Example 1 (NiO) x Comparison of UV photoelectron spectroscopy measurements for / Me-4PACz / TCDJ; Figure 2 Comparative Example 1 (NiO) x / Me-4PACz) and Example 1 (NiO) x Comparison of conductivity tests for / Me-4PACz / TCDJ; Figure 3 The phosphorus NMR spectrum of pure Me-4PACz in deuterated methanol is shown in Comparative Example 1. Figure 4 The phosphorus NMR spectrum of the Me-4PACz / TCDJ mixed solution in deuterated methanol in Example 1 is shown. Figure 5 Comparative Example 1 (NiO) xKelvin probe force microscopy potential distribution on the surface of / Me-4PACz); Figure 6 Example 1 (NiO) x Kelvin probe force microscopy potential distribution on the surface of / Me-4PACz / TCDJ; Figure 7 Perovskite precursor solution in Comparative Example 1 (NiO x Contact angle test diagram of the surface of / Me-4PACz); Figure 8 Perovskite precursor solution in Example 1 (NiO x Contact angle test diagram of the surface of / Me-4PACz / TCDJ); Figure 9 For comparative example 1 (NiO) x Scanning electron microscope image of the buried interface of the perovskite film grown on / Me-4PACz); Figure 10 In Example 1 (NiO) x Scanning electron microscope image of the buried interface of the perovskite film grown on / Me-4PACz / TCDJ). Figure 11 Based on the hole transport layer (NiO) of Comparative Example 1 x Space charge confinement current test curve of perovskite thin film prepared by / Me-4PACz; Figure 12 Based on the hole transport layer (NiO) of Example 1 x Space charge confinement current test curve of perovskite thin film prepared by / Me-4PACz / TCDJ; Figure 13 The Mott-Schottky curves of the perovskite solar cell devices fabricated based on the hole transport layers of Comparative Example 1 and Example 1 are shown in comparison. Figure 14 Comparison of time-resolved photoluminescence decay spectra of perovskite films deposited on hole transport layers in Comparative Example 1 and Example 1. Figure 15 A comparison of the current density-voltage characteristic curves of the inverted wide-bandgap perovskite solar cells prepared in Comparative Example 1 and Example 1. Figure 16 This is a schematic diagram of the structure of the inverted wide-bandgap perovskite solar cell described in this invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the prior art, on the one hand, self-assembled molecules (such as Me-4PACz) in nickel oxide (NiO) x During surface modification, clustering and aggregation can easily occur, leading to poor surface coverage of the hole transport layer, poor film uniformity, and consequently, technical problems such as poor interfacial contact and increased leakage current. On the other hand, traditional NiO... x The intrinsic conductivity of the self-assembled molecular composite hole transport layer is low, and the interface charge extraction and transport kinetics are insufficient, resulting in a large series resistance (Rs) of the cell and making it difficult to obtain a high photoelectric conversion efficiency (PCE). On the other hand, in inverted wide-bandgap perovskite solar cells, there are a large number of unsaturated defects (such as cation vacancies or lattice distortions) at the "buried interface" between the hole transport layer and the perovskite layer, which leads to severe nonradiative recombination of charge carriers, thereby limiting the improvement of the device open-circuit voltage (Voc) and fill factor (FF).

[0025] In view of this, the present invention employs an additive for the hole transport layer (Me-4PACz) of an inverted wide-bandgap perovskite solar cell. This additive is betaine hydrochloride. The prepared perovskite solar cell consists of a transparent conductive substrate, nickel oxide nanoparticles, a hole transport layer, an organic-inorganic hybrid metal halide perovskite light-absorbing layer, a metal fluoride layer, an electron transport layer, a hole-blocking layer, and a metal electrode. With the addition of this additive, Me-4PACz, due to the carboxylic acid groups in its molecule, can react with NiO. x Surface interactions occur, modulating Ni 3+ / Ni 2+ The ratio of betaine hydrochloride to Me-4PACz is adjusted to improve the conductivity of the hole transport layer. Simultaneously, the interaction between this molecule and Me-4PACz effectively regulates their intermolecular arrangement, inhibiting the self-aggregation behavior of phosphonic acid groups through steric hindrance and intermolecular interactions, thereby hindering the cluster formation of Me-4PACz and achieving a more uniform interface coverage. Furthermore, the carboxyl and quaternary ammonium groups on betaine hydrochloride can passivate defects in the perovskite film. However, excessive use of betaine hydrochloride can lead to competition for coordination with Me-4PACz, resulting in a decrease in charge transport performance. Therefore, using an appropriate amount of betaine hydrochloride effectively improves the conductivity of the nickel oxide layer, improves the clustering behavior of Me-4PACz, making its distribution more uniform, and passivates defects at the buried interface of the perovskite light-absorbing layer, thus improving the photoelectric conversion efficiency.

[0026] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In this document, the terms “containing,” “comprising,” or “including” are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0028] In this document, the terms “optional,” “optionally,” or “optional” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0030] Unless otherwise specified, all raw materials used in this invention are commercially available. Specifically, ITO conductive glass, nickel oxide nanoparticles, and (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (Me-4PACz) were purchased from Liaoning Youxuan Technology Co., Ltd.; betaine hydrochloride was purchased from Maclean Reagent Co., Ltd.; CsI, RbI, MABr, FAI, PbI2, and PbBr2 were purchased from Xi'an Yuri Solar Energy Technology Co., Ltd.; and N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were purchased from Sigma Reagent Co., Ltd.

[0031] In a specific embodiment, the present invention provides a hole transport layer containing betaine hydrochloride additive and a method for preparing an inverse wide-bandgap perovskite solar cell, comprising the following steps: (1) The transparent conductive substrate is ultrasonically cleaned sequentially with deionized water, acetone and anhydrous ethanol, with each cleaning time being 15 min; the transparent conductive substrate includes one of laser-etched ITO conductive glass and FTO conductive glass. (2) Preparation of hole transport layer: Nickel oxide nanoparticles were dispersed in deionized water at a concentration of 10 mg / mL and prepared by spin coating. The spin coating parameters were 4000 rpm, 1000 rpm acceleration, and 30 s rotation time. Then, the mixture was annealed at 120℃ for 15 min, and the thickness was 10~15 nm. Subsequently, (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (Me-4PACz) and betaine hydrochloride (TCDJ) were mixed and dissolved in ethanol at concentrations of 0.5 mg / mL and 0.023~0.046 mg / mL, respectively. The mixture was prepared on nickel oxide film by spin coating. The spin coating parameters were 3000 rpm, 1000 rpm acceleration, and 30 s rotation time. The mixture was annealed at 100℃ for 15 min, and the thickness was 1~3 nm. (3) Cs 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.35 3. Perovskite precursor powder was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and an organic-inorganic hybrid metal halide perovskite light-absorbing layer with a thickness of 400 nm was prepared by spin coating. The precursor powder included CsI, RbI, MABr, FAI, PbI2, and PbBr2 weighed in stoichiometric ratio; wherein the volume ratio of DMF to DMSO was 4:1, and the concentration of the perovskite precursor solution was 0.8~1.25 mmol / mL. (4) The obtained precursor solution was uniformly spread onto the NiO treated with Me-4PACz and TCDJ. x On the substrate, chlorobenzene was used as an antisolvent to assist in film formation. A two-stage spin coating method was used. The first stage was at a speed of 1000 rpm for 10 s, and the second stage was at a speed of 4000 rpm for 30 s. 100~200 μL of chlorobenzene was added dropwise at the 15th second before the end of the second stage. The optimal temperature for the spin coating process was 18~20℃. (5) Anneal the obtained perovskite film at 100°C for 30 min; (6) Post-treatment of the annealed perovskite film: Dynamically spin-coat 2 mg / mL octyl bromide solution onto the spin-coated perovskite film and anneal at 100℃ for 5 min; (7) A metal fluoride layer is prepared on the surface of a perovskite thin film by thermal evaporation, wherein the metal fluoride layer is one of LiF, MgF2, and NaF, and the thickness is 1 nm; (8) An electron transport layer is prepared on the surface of a metal fluoride layer by thermal evaporation, wherein the electron transport layer is a fullerene derivative and has a thickness of 25~30 nm; (9) A hole blocking layer is prepared on the surface of the electron transport layer by thermal evaporation. The hole blocking layer is copper bath (BCP) with a thickness of 7 nm. (10) A metal electrode is prepared on the surface of the hole blocking layer by thermal evaporation. The metal electrode is one of Ag, Cu, and Au, and the thickness is 80~100 nm.

[0032] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0033] Example 1

[0034] This embodiment provides a method for preparing a hole transport layer containing betaine hydrochloride additive and an inverse wide-bandgap perovskite solar cell, including the following steps: (1) The etched ITO conductive glass was ultrasonically cleaned in sequence with deionized water, acetone and anhydrous ethanol, with each cleaning time being 15 min. (2) Preparation of hole transport layer: Nickel oxide nano-dispersed particles were dissolved in deionized water at a concentration of 10 mg / mL and prepared by spin coating. The spin coating parameters were 4000 rpm, acceleration 1000 rpm, and rotation time 30 s. Then, the mixture was annealed at 120℃ for 15 minutes, and the thickness was 12 nm. Subsequently, Me-4PACz and TCDJ were mixed at 0.5 mg / mL and 0.03 mg / mL respectively and dissolved in ethanol. The mixture was prepared on nickel oxide film by spin coating. The spin coating parameters were 3000 rpm, acceleration 1000 rpm, and rotation time 30 s. The mixture was annealed at 100℃ for 15 minutes, and the thickness was 2 nm. (3) Cs 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.35 3. Perovskite precursor powder was dissolved in a mixed solvent of DMF and DMSO, and an organic-inorganic hybrid metal halide perovskite light-absorbing layer with a thickness of 400 nm was prepared by spin coating. The precursor powder included CsI, RbI, MABr, FAI, PbI2, and PbBr2 weighed according to stoichiometric ratio. The volume ratio of DMF to DMSO was 4:1, and the concentration of the perovskite precursor solution was 1 mmol / mL. (4) The obtained precursor solution was uniformly spread onto the NiO treated with Me-4PACz and TCDJ. xOn the substrate, chlorobenzene was used as an antisolvent to assist in film formation. A two-stage spin coating method was used. The first stage was at a speed of 1000 rpm for 10 s, and the second stage was at a speed of 4000 rpm for 30 s. 150 μL of chlorobenzene was added dropwise at the 15th second before the end of the second stage. The spin coating temperature was 19℃. (5) Anneal the obtained perovskite film at 100°C for 30 min; (6) Post-treatment of the annealed perovskite film: Dynamically spin-coat 2 mg / mL octyl bromide solution onto the spin-coated perovskite film and anneal at 100℃ for 5 min; (7) A metal fluoride layer is prepared on the surface of a perovskite thin film by thermal evaporation. The metal fluoride layer is LiF and has a thickness of 1 nm. (8) An electron transport layer is prepared on the surface of a metal fluoride layer by thermal evaporation. The electron transport layer is C60 and has a thickness of 28 nm. (9) A hole blocking layer is prepared on the surface of the electron transport layer by thermal evaporation. The hole blocking layer is copper bath (BCP) with a thickness of 7 nm. (10) A metal electrode is prepared on the surface of the hole blocking layer by thermal evaporation. The metal electrode is Ag and has a thickness of 90 nm.

[0035] Example 2

[0036] This embodiment provides a method for preparing a hole transport layer containing betaine hydrochloride additive and an inverse wide-bandgap perovskite solar cell, including the following steps: (1) The etched ITO conductive glass was ultrasonically cleaned in sequence with deionized water, acetone and anhydrous ethanol, with each cleaning time being 15 min. (2) Preparation of hole transport layer: Nickel oxide nano-dispersed particles were dissolved in deionized water at a concentration of 10 mg / mL and prepared by spin coating with a thickness of 10 nm; then Me-4PACz and TCDJ were mixed at 0.5 mg / mL and 0.023 mg / mL respectively and dissolved in ethanol, and prepared on nickel oxide film by spin coating with a thickness of 1 nm. (3) Cs 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.353. Perovskite precursor powder was dissolved in a mixed solvent of DMF and DMSO, and an organic-inorganic hybrid metal halide perovskite light-absorbing layer with a thickness of 400 nm was prepared by spin coating. The precursor powder included CsI, RbI, MABr, FAI, PbI2, and PbBr2 weighed according to stoichiometric ratio. The volume ratio of DMF to DMSO was 4:1, and the concentration of the perovskite precursor solution was 0.8 mmol / mL. (4) The obtained precursor solution was uniformly spread onto the NiO treated with Me-4PACz and TCDJ. x On the substrate, chlorobenzene was used as an antisolvent to assist in film formation. A two-stage spin coating method was used. The first stage was at a speed of 1000 rpm for 10 s, and the second stage was at a speed of 4000 rpm for 30 s. 100 μL of chlorobenzene was added dropwise at the 15th second before the end of the second stage. The spin coating temperature was 18℃. (5) Anneal the obtained perovskite film at 100°C for 30 min; (6) Post-treatment of the annealed perovskite film: Dynamically spin-coat 2 mg / mL octyl bromide solution onto the spin-coated perovskite film and anneal at 100℃ for 5 min; (7) A metal fluoride layer is prepared on the surface of a perovskite thin film by thermal evaporation. The metal fluoride layer is LiF and has a thickness of 1 nm. (8) An electron transport layer is prepared on the surface of a metal fluoride layer by thermal evaporation, wherein the electron transport layer is C60 and has a thickness of 25 nm; (9) A hole blocking layer is prepared on the surface of the electron transport layer by thermal evaporation. The hole blocking layer is copper bath (BCP) with a thickness of 7 nm. (10) A metal electrode is prepared on the surface of the hole blocking layer by thermal evaporation. The metal electrode is Ag and has a thickness of 80 nm.

[0037] Example 3

[0038] This embodiment provides a method for preparing a hole transport layer containing betaine hydrochloride additive and an inverse wide-bandgap perovskite solar cell, including the following steps: (1) The etched ITO conductive glass was ultrasonically cleaned in sequence with deionized water, acetone and anhydrous ethanol, with each cleaning time being 15 min. (2) Preparation of hole transport layer: Nickel oxide nano-dispersed particles were dissolved in deionized water at a concentration of 10 mg / mL and prepared by spin coating with a thickness of 15 nm; then Me-4PACz and TCDJ were mixed at 0.5 mg / mL and 0.046 mg / mL respectively and dissolved in ethanol, and prepared on nickel oxide film by spin coating with a thickness of 3 nm. (3) Cs 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.35 3. Perovskite precursor powder was dissolved in a mixed solvent of DMF and DMSO, and an organic-inorganic hybrid metal halide perovskite light-absorbing layer with a thickness of 400 nm was prepared by spin coating. The precursor powder included CsI, RbI, MABr, FAI, PbI2, and PbBr2 weighed according to stoichiometric ratio. The volume ratio of DMF to DMSO was 4:1, and the concentration of the perovskite precursor solution was 1.25 mmol / mL. (4) The obtained precursor solution was uniformly spread onto the NiO treated with Me-4PACz and TCDJ. x On the substrate, chlorobenzene was used as an antisolvent to assist in film formation. A two-stage spin coating method was used. The first stage was at a speed of 1000 rpm for 10 s, and the second stage was at a speed of 4000 rpm for 30 s. 200 μL of chlorobenzene was added dropwise at the 15th second before the end of the second stage. The spin coating temperature was 20℃. (5) Anneal the obtained perovskite film at 100°C for 30 min; (6) Post-treatment of the annealed perovskite film: Dynamically spin-coat 2 mg / mL octyl bromide solution onto the spin-coated perovskite film and anneal at 100℃ for 5 min; (7) A metal fluoride layer is prepared on the surface of a perovskite thin film by thermal evaporation. The metal fluoride layer is LiF and has a thickness of 1 nm. (8) An electron transport layer is prepared on the surface of a metal fluoride layer by thermal evaporation, wherein the electron transport layer is C60 and has a thickness of 30 nm; (9) A hole blocking layer is prepared on the surface of the electron transport layer by thermal evaporation. The hole blocking layer is copper bath (BCP) with a thickness of 7 nm. (10) A metal electrode is prepared on the surface of the hole blocking layer by thermal evaporation. The metal electrode is Ag and has a thickness of 100 nm.

[0039] Comparative Example 1 This comparative example provides a method for preparing a hole transport layer and an inverted wide-bandgap perovskite solar cell, but without betaine hydrochloride additive; the difference from Example 1 is that betaine hydrochloride is not added in step 2), while the other steps remain the same.

[0040] Comparative Example 2 This comparative example provides a hole transport layer containing betaine hydrochloride additive and a method for preparing an inverted wide-bandgap perovskite solar cell; the difference from Example 1 is that: in step 2), 0.08 mg / ml of betaine hydrochloride is added, while the other steps remain the same.

[0041] Comparative Example 3 This comparative example provides a hole transport layer containing betaine hydrochloride additive and a method for preparing an inverted wide-bandgap perovskite solar cell; the difference from Example 1 is that: in step 2), 0.01 mg / ml of betaine hydrochloride is added, while the other steps remain the same.

[0042] To verify the effect of betaine hydrochloride additive on Me-4PACz and NiO x The effects of perovskite light-absorbing layer and final solar cell device performance were investigated through a series of performance tests and analyses.

[0043] See Figure 1 This invention relates to NiO x / Me-4PACz (Comparative Example 1) and NiO x Ultraviolet photoelectron spectroscopy (EPS) was performed on two hole transport layer solid film samples, / Me-4PACz / TCDJ (Example 1), demonstrating that the introduction of the additive (betaine hydrochloride) via its carboxylic acid groups interacts with NiO. x Interactions enhance surface Ni 3+ The proportion of Ni. 3+ It is the main source of hole carriers, which explains the increase in conductivity.

[0044] See Figure 2 This invention relates to NiO x / Me-4PACz (Comparative Example 1) and NiO x Conductivity tests were performed on two hole transport layer solid film samples, / Me-4PACz / TCDJ (Example 1), demonstrating that the addition of betaine hydrochloride significantly improved the conductivity of the hole transport layer and enhanced its charge transport capability.

[0045] See Figures 3-4 This invention involves performing NMR spectroscopy (NMR) on a pure Me-4PACz ethanol solution (Comparative Example 1) and a mixed ethanol solution of Me-4PACz and TCDJ (Example 1) in deuterated methanol. The shift in the phosphine peak demonstrates an interaction between betaine hydrochloride and the phosphonic acid groups in Me-4PACz. This is crucial for inhibiting the self-aggregation of Me-4PACz and improving its performance in NiO. x Direct molecular-level evidence of uniform surface distribution.

[0046] See Figures 5-6 This invention relates to NiOx / Me-4PACz (Comparative Example 1) and NiO x Kelvin probe force microscopy was performed on two hole transport layer solid film samples, / Me-4PACz / TCDJ (Example 1). The average surface potential decreased from 44.5 mV to 13.8 mV, proving that the potential distribution on the film surface became extremely uniform after the addition of the additive, and the potential fluctuation value was significantly reduced. This reflects a significant improvement in the uniformity of the Me-4PACz molecular layer coverage, verifying the conclusion of NMR.

[0047] See Figures 7-8 This invention relates to NiO x / Me-4PACz (Comparative Example 1) and NiO x / Me-4PACz / TCDJ (Example 1) The contact angle of the perovskite precursor solution on the surface of two hole transport layer solid film samples was tested. The addition of betaine hydrochloride reduced the contact angle of the perovskite precursor solution at the interface from 20° to 12°, proving that the wettability of the modified hole transport layer surface to the perovskite precursor solution was significantly improved. Better wettability is a prerequisite for forming a uniform, pore-free perovskite film.

[0048] See Figures 9-10 This invention relates to NiO x / Me-4PACz (Comparative Example 1) and NiO x Scanning electron microscopy (SEM) tests were performed on perovskite films grown on two hole transport layers, / Me-4PACz / TCDJ (Example 1). The perovskite film grown on the modified hole transport layer showed a denser and smoother buried interface with a significant reduction in pore defects. This is a direct result of the improved contact angle and is also the structural basis for obtaining high-performance devices.

[0049] See Figures 11-12 The present invention is based on NiO x / Me-4PACz (Comparative Example 1) and NiO x / Me-4PACz / TCDJ (Example 1) Space-confined charge current testing was performed on wide-bandgap perovskite films deposited on two hole transport layers (test structure was NiO). x (Me-4PACz / PSK / PTAA) demonstrates that the defect state density inside the perovskite film grown on the modified hole layer is significantly reduced; defects are traps that lead to carrier recombination, and the fewer defects, the better the performance.

[0050] See Figure 13 This invention relates to NiO x / Me-4PACz (Comparative Example 1) and NiO xThe Mott-Schottky curves of perovskite solar cell devices fabricated on two hole transport layers (Example 1) are compared, demonstrating that the device based on the modified hole layer has superior interface characteristics.

[0051] See Figure 14 The present invention is based on NiO x / Me-4PACz (Comparative Example 1) and NiO x Time-resolved photoluminescence spectroscopy tests were performed on wide-bandgap perovskite films deposited on two hole transport layers, namely / Me-4PACz / TCDJ (Example 1). The results showed that the nonradiative recombination of photogenerated carriers in the perovskite film grown on the modified hole layer was effectively suppressed, and the lifetime was significantly extended.

[0052] join Figure 15 The inverse wide-bandgap perovskite solar cells prepared in Comparative Example 1 and Example 1 of this invention were tested for current density-voltage curves. The cells using the modified hole layer of this invention showed an overall upward shift in their JV curves, higher open-circuit voltage, larger fill factor, and ultimately higher efficiency.

[0053] See Figure 16 This is a schematic diagram of the inverted wide-bandgap perovskite solar cell structure in this invention.

[0054] Table 1 compares the performance parameters of the inverted wide-bandgap perovskite solar cells prepared by Comparative Example 1 (Control), Example 1 (Target), and other examples and comparative examples of the present invention.

[0055] Table 1 Performance parameters of the inverse wide-bandgap perovskite solar cells prepared by this invention

[0056] Data shows that the implementation of this invention reduces the device open-circuit voltage (V oc The voltage was increased from about 1.30 V to over 1.35 V, the fill factor (FF) was increased by about 5 percentage points, and the final photoelectric conversion efficiency (PCE) was significantly increased from about 19.5% to over 21.7%.

[0057] Comparative Example 2 shows that when the amount of betaine hydrochloride added is too high, the filling capacity and current of the prepared device are significantly reduced compared to Example 1. This indicates that excessive betaine hydrochloride occupies the Me-4PACz sites, severely hindering carrier transport and thus leading to a decrease in device performance.

[0058] The results of Comparative Example 3 show that when the amount of betaine hydrochloride added is too low, the performance of the prepared device is significantly improved compared with Comparative Example 1, but not as good as that of Examples 1-3. This indicates that a low content of betaine hydrochloride can produce an optimization effect on the device, but the optimization effect is not optimal, and there are still some unpassivated defects at the device interface.

[0059] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A hole transport layer for perovskite solar cells, characterized in that, include: Nickel oxide layer; And a self-assembled molecular layer formed on the surface of the nickel oxide layer; The self-assembled molecular layer comprises (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride.

2. The hole transport layer according to claim 1, characterized in that, The amount of betaine hydrochloride added is 10% to 20% of the molar amount of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid.

3. The hole transport layer according to claim 1, characterized in that, The thickness of the nickel oxide layer is 10~15 nm; the thickness of the self-assembled molecular layer is 1~3 nm.

4. A method for preparing a hole transport layer as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1-1. Disperse nickel oxide in deionized water and then spin-coat it onto the surface of a transparent conductive substrate to obtain a nickel oxide layer. S1-2. Dissolve (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride in ethanol to obtain a mixed solution, and then spin-coat it onto the surface of the nickel oxide layer to obtain a hole transport layer.

5. The preparation method according to claim 4, characterized in that, In the mixed solution of steps S1-2, the concentration of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid is 0.5 mg / mL; and the concentration of betaine hydrochloride is 0.023~0.046 mg / mL.

6. A perovskite solar cell, characterized in that, It comprises a transparent conductive substrate, a hole transport layer as described in any one of claims 1 to 3, an organic-inorganic hybrid metal halide perovskite light-absorbing layer, a metal fluoride layer, an electron transport layer, a hole blocking layer, and a metal electrode, which are stacked sequentially.

7. The perovskite solar cell according to claim 6, characterized in that, The organic-inorganic hybrid metal halide perovskite light-absorbing layer contains Cs 0.05 Rb 0.05 MA 0.05 FA 0.85 Pb(I 0.65 Br 0.35 3; the metal fluoride layer is selected from LiF, MgF2 or NaF; the electron transport layer contains a fullerene derivative; the hole blocking layer contains copper bath; the metal electrode is selected from Ag, Cu or Au.

8. The perovskite solar cell according to claim 6, characterized in that, The thickness of the electron transport layer is 25-30 nm; the thickness of the metal electrode is 80-100 nm.

9. A method for preparing a perovskite solar cell according to any one of claims 6 to 8, characterized in that, Includes the following steps: S1. Provide a transparent conductive substrate and clean it; S2. Prepare a nickel oxide layer on the cleaned substrate; S3. Spin-coat the nickel oxide layer with a mixed solution containing (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid and betaine hydrochloride to form a self-assembled molecular layer and obtain a hole transport layer. S4. Spin-coat the perovskite precursor solution onto the hole transport layer, and then perform antisolvent-assisted crystallization and annealing to form a perovskite light-absorbing layer. S5. On the perovskite light-absorbing layer, a metal fluoride layer, an electron transport layer, a hole blocking layer, and a metal electrode are sequentially prepared.

10. The preparation method according to claim 9, characterized in that, The concentration of the perovskite precursor solution is 0.8~1.25 mmol / mL.

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