Perovskite solar cell based on cross-linked interfacial passivation layer

Abstract

The application discloses a perovskite solar cell based on a cross-linking interface passivation layer and relates to the technical field of photovoltaic cell materials. The perovskite solar cell comprises, from bottom to top, a transparent conductive substrate, an electron transport layer, a perovskite light absorption layer, a cross-linking interface passivation layer, a hole transport layer and a metal electrode. The cross-linking interface passivation layer is a 4-[10-(4-{1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid material. The cross-linking interface passivation layer can significantly improve the photovoltaic performance and stability, and the cross-linking network greatly enhances the intrinsic stability of the device. In a double 85 aging test at 85 DEG C / 85%RH, the time required for the device efficiency to decay to 80% of the initial value can be more than 1000 hours.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cell materials, and particularly relates to a perovskite solar cell based on a cross-linked interface passivation layer. BACKGROUND

[0002] Existing research shows that passivation of perovskite defects by additives is an effective means to improve performance. For example, patent CN115623842A discloses a perovskite material and a preparation method and application thereof. A self-crosslinkable organic small molecule additive, such as N,N-methylene bisacrylamide, is added to the perovskite precursor solution of a solar cell. Compared with a solar cell without doping, the device efficiency and light, heat and humidity stability are significantly improved. CN117304432A discloses a preparation method of a long alkane phosphonic acid branched conjugated covalent organic framework material. The introduction of long alkane phosphonic acid branches improves the dispersibility and solubility of the conjugated covalent organic framework material. When applied to modified perovskite thin films and photovoltaic cells, it can effectively improve the crystalline quality of perovskite crystals, reduce internal defects, promote interface charge transport, and significantly improve the photoelectric conversion efficiency. However, these methods have limitations: first, small molecule additives usually only act on a certain type of defects in the perovskite phase or surface, and the passivation is not comprehensive, with a single action site; second, small molecules may migrate or volatilize under long-term thermal stress or light, resulting in ineffective passivation and insufficient stability; third, the additive may damage the interface contact between the perovskite and the charge transport layer, with poor interface compatibility.

[0003] Patent CN120040460A discloses a hole transport material and a preparation method and perovskite solar cell thereof. The quinoxaline moiety is extended conjugated modified as an electron acceptor, introducing multiple triphenylamine electron-donating groups, dihydronaphthalene, binaphthyl oxy and other single donors to construct a hole transport material with a multi-donor structure. This hole transport material adjusts the distribution of HOMO-LUMO, increases the charge transfer channel, and improves the separation and transport capacity of charges, thereby improving the mobility of carriers. Although this technical solution focuses on the interface layer and the hole transport material, it fails to integrate perovskite bulk phase passivation and interface modification synergistically, and the stability is still insufficient. SUMMARY

[0004] The present application aims to provide a novel multifunctional interface passivation layer and a preparation method thereof. The passivation layer can form a stable “bridge” between the perovskite and the hole transport layer, and simultaneously realize bulk phase defect passivation, interface energy level optimization and internal hydrophobic protection, thereby preparing a perovskite solar cell with high efficiency and high stability.

[0005] The core of the present application is to design and synthesize a multi-dentate ligand molecular compound (hereinafter referred to as DCL) with cross-linking function, and apply it to the lower interface of perovskite to form a cross-linked interface passivation layer.

[0006] I) DCL design:

[0007] Structural features of DCL: The general formula of the molecular structure is Anchor-π-Bridge-Crosslinker;

[0008] Anchor (anchor group): phosphate group. This group can form a strong coordination bond with lead ions in perovskite, effectively passivating uncoordinated Pb 2+ defects, firmly anchored on the perovskite surface;

[0009] π-Bridge (π bridge): phenoxazine. This structure has good hole transport performance, can optimize the interface energy level alignment, promote hole extraction, and its electron-rich characteristics can further passivate halogen vacancy defects;

[0010] Crosslinker (crosslinking group): trifluorovinyl ether. This group can undergo in-situ polymerization and crosslinking under mild thermal annealing conditions, forming an insoluble polymer network to form a stable protective layer.

[0011] II) DCL preparation

[0012] The DCL used in the present application is specifically 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid (structure formula as follows Formula (I), referred to as target molecule) material;

[0013] Formula (I).

[0014] The preparation method of the target molecule is as follows:

[0015] 1) Synthesis method of 4-boronate phenylphosphonic acid diethyl ester

[0016] Step 1.1: Synthesis of 4-bromophenylphosphonic acid diethyl ester (as follows Formula (1.1))

[0017] Formula (1.1)

[0018] Procedure: A dry 100 mL three-necked flask was fitted with a constant pressure dropping funnel, a nitrogen inlet tube and a thermometer. The flask was charged with 4-bromophenol 1.73 g and a magnetic stir bar. The flask was evacuated and flushed with nitrogen three times to ensure an inert atmosphere. Anhydrous dichloromethane 20 mL was added and the stirring started to dissolve the 4-bromophenol. Triethylamine 2.1 mL was added via syringe. The flask was placed in an ice-water bath and cooled to 0 °C. Diethyl phosphite 1.4 mL was mixed with 5 mL of anhydrous dichloromethane in a dry vial and the mixture was transferred to the constant pressure dropping funnel. The diethyl phosphite solution was added slowly to the reaction flask at 0 °C over 15-20 minutes. After the addition was complete, the stirring was continued at 0 °C for 30 minutes. The ice-water bath was removed and the reaction mixture was allowed to warm to room temperature and the stirring was continued for 4-6 hours (the progress of the reaction can be monitored by TLC). After the reaction was complete, the reaction was quenched by the addition of 20 mL of water. The reaction mixture was transferred to a separatory funnel and the organic phase was separated. The aqueous phase was extracted twice with dichloromethane (15 mL x 2). The combined organic phase was washed once with saturated brine (20 mL). The organic phase was dried over anhydrous sodium sulfate, filtered and the filtrate was concentrated on a rotary evaporator to give the crude product. The crude product was purified by column chromatography on silica gel. The product was eluted with a gradient of petroleum ether / ethyl acetate (from 5:1 to 2:1, v / v). The progress of the purification was monitored by TLC (petroleum ether / ethyl acetate = 3:1, product spot at Rf ≈ 0.3-0.4). The fractions containing the product were collected and concentrated to give 4-bromophenyl diethyl phosphonate as a colorless to pale yellow oil (75% yield).

[0019] Step 1.2: Synthesis of 4-boronate phenyl diethyl phosphonate (as formula (1.2) below)

[0020] Formula (1.2)

[0021] Procedure: A dry 50 mL Schlenk tube was charged with a magnetic stir bar, evacuated and filled with nitrogen three times; under a stream of nitrogen, the tube was charged with the product from step 1.1 (1.55 g), bis(pinacolato)diboron (1.52 g), potassium acetate (1.47 g), and Pd(dppf)Cl2 122 mg; the reaction tube was then charged with 15 mL of degassed dry dioxane using a syringe, the walls of the tube were rinsed and the solids were allowed to soak, the reaction tube was then briefly flushed with a stream of nitrogen, and then tightly sealed. The reaction was placed in a preheated 90 °C oil bath and stirred vigorously for 12-16 hours; after the reaction was complete, the reaction tube was cooled to room temperature and the reaction mixture was filtered through a small pad of celite, the filter cake was washed with several small portions of dichloromethane, the filtrates were combined and concentrated using a rotary evaporator to give the crude product; the crude product was purified by silica gel column chromatography using a gradient of petroleum ether / ethyl acetate (from 4:1 to 1:1, v / v); TLC monitoring (petroleum ether / ethyl acetate = 2:1, product spot at Rf ~ 0.2-0.3); the fractions of interest were collected and concentrated to give 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl diethyl phosphate as a white or off-white solid (87% yield).

[0022] 2) Synthesis of (10-(4-((trifluorovinyl)oxy)phenyl)-2-iodophenoxazine)

[0023] Step 2.1: Synthesis of 10-(4-hydroxyphenyl)phenoxazine (as formula (2.1) below)

[0024] Formula (2.1)

[0025] Procedure: In a 250 mL dry Schlenk flask, phenoxazine 5.00 g, p-iodophenol 7.23 g, cesium carbonate 22.1 g, copper powder 173 mg, and 18-crown-6 150 mg were sequentially added; the flask was evacuated and filled with nitrogen three times; under a stream of nitrogen, 100 mL of dry DMSO was added; the mixture was heated to 130 °C and stirred for 12 hours; after the reaction was complete, the mixture was cooled to room temperature and poured into 300 mL of ice water, a large amount of solid precipitated; the mixture was filtered under suction and the filter cake was washed with water and dried under vacuum; the crude product was dissolved in dichloromethane and purified by silica gel column chromatography (eluent: dichloromethane / methanol = 20:1, v / v) to give the product as a white solid (75% yield).

[0026] Step 2.2: Synthesis of 10-(4-((trifluorovinyl)oxy)phenyl)phenoxazine (as formula (2.2) below)

[0027] Formula (2.2)

[0028] Procedure: In a dry 100 mL Schlenk flask, add the product from Step 2.1, 5.00 g, and cesium carbonate, 5.28 g, sequentially; vacuum and fill with nitrogen, repeat three times; under nitrogen protection, inject anhydrous DMF 75 mL, cool to 0°C with an ice water bath; slowly drop 2-bromo-1,1,2-trifluoroethylene 3.0 mL with a syringe; after the drop is complete, let the reaction system naturally warm to room temperature, continue stirring for 5 hours; after monitoring the reaction completion by TLC, pour the reaction liquid into 200 mL ice water, extract with ethyl acetate (3 x 100 mL); wash the combined organic phase with saturated brine (3 x 80 mL) to remove DMF; dry over anhydrous sodium sulfate, filter, and concentrate by rotary evaporation; purify by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 10:1, v / v) to obtain the product as a light yellow oil (yield 80%).

[0029] Step 2.3: Synthesis of (10-(4-((trifluorovinyl)oxy)phenyl)-2-iodophenoxazine) (as Formula (2.3) below)

[0030] Formula (2.3)

[0031] Procedure: In a dry round-bottom flask, dissolve the product from Step 2.2, 1.00 g, in anhydrous dichloromethane 25 mL, add a few drops of trifluoroacetic acid (catalytic reaction); under ice water bath cooling (0°C) and dark conditions, slowly add N-iodosuccinimide (NIS) 0.62 g in batches; remove the ice bath, let the reaction mixture slowly warm to room temperature, and stir the reaction at room temperature for 2-4 hours; monitor the reaction progress by TLC; after the reaction is complete, quench the reaction with saturated aqueous sodium thiosulfate solution to remove residual iodine; extract the mixture with dichloromethane, combine the organic phases, and wash separately with saturated sodium thiosulfate solution and brine; dry the organic phase over anhydrous sodium sulfate, filter, and concentrate by rotary evaporation; purify the crude product quickly by silica gel column chromatography (eluent: petroleum ether / ethyl acetate) to obtain the product as a light yellow solid (yield 78%).

[0032] 3) Assembly and purification of target molecules

[0033] Step 3.1: Suzuki-Miyaura coupling reaction

[0034] Procedure: In a 100 mL dry Schlenk flask, the product from step 2.3 1.20 g, the product from step 1.2 0.70 g and tetrakis(triphenylphosphine)palladium 106 mg were added successively; vacuumed and filled with nitrogen, repeated for three times; degassed 2M aqueous potassium carbonate solution 2.75 mL and toluene / ethanol mixed solvent (toluene 15 mL, ethanol 4 mL) were added successively by syringe; the reaction system was heated to 90 °C under nitrogen protection, and stirred at reflux for 12 hours at this temperature; the reaction progress was monitored by TLC; after the reaction was completed, the reaction mixture was cooled to room temperature; 30 mL of water was added, extracted with dichloromethane (3 x 30 mL); the organic phase was combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated by rotary evaporator to remove the solvent to obtain the crude product; the crude product was purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 3:1, v / v) to obtain 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenyl diethyl phosphate (as formula (3.1) below) as a light yellow foamy solid (yield 80%);

[0035] Formula (3.1)

[0036] Step 3.2: Hydrolysis of phosphonate ester

[0037] Procedure: In a 50 mL dry round-bottom flask, the product from step 3.1 0.70 g was dissolved in anhydrous dichloromethane; the reaction flask was cooled to 0 °C in an ice water bath; under nitrogen protection and stirring, trimethylsilyl bromide 1.0 mL was slowly added dropwise by syringe; after the addition was completed, the ice bath was removed, and the reaction mixture was stirred at room temperature for 5 hours. The reaction completion was monitored by TLC (the raw material point disappeared); after the reaction was completed, the reaction liquid was carefully poured into 20 mL ice water; the pH of the aqueous phase was slowly adjusted to 6.8 with 1M aqueous sodium hydroxide solution; the aqueous and organic phases were separated, and the aqueous phase was washed with dichloromethane (15 mL); the combined organic phases were dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation; the crude product was finally purified by preparative high performance liquid chromatography (C18 reversed phase column, acetonitrile / water containing 0.1% formic acid as mobile phase gradient elution) to obtain the final target product 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenyl phosphonic acid (formula (I)) as a light yellow solid (yield 85%).

[0038] Characterization of the final target product:

[0039] 1H NMR (400 MHz, DMSO-d6) δ: 8.5-10.5 (br s, 2H), 8.05 (d, J = 8.2 Hz, 2H), 7.80 (d, J = 8.2 Hz, 2H), 7.45-7.60 (m, 4H), 6.70-7.40 (m, 8H), 6.10-6.25 (dq, J = 6.5, 1.5 Hz, 1H).

[0040] 31 P NMR (162 MHz, DMSO-d6) δ: 18.5.

[0041] HRMS (ESI-) m / z: [M-H]⁻calcd for C 26 H 17 F3NO5P: 511.385; found:510.3780 9.

[0042] III) Structure and preparation of perovskite solar cells

[0043] The perovskite solar cell structure of the present application is sequentially from bottom to top: transparent conductive substrate, electron transport layer, perovskite light absorption layer, cross-linked interface passivation layer (composed of DCL), hole transport layer, metal electrode.

[0044] The preparation steps of the cross-linked interface passivation layer are as follows: depositing the perovskite light absorption layer on the electron transport layer and performing preliminary annealing to form crystals; dissolving DCL in a mild anti-solvent, spin coating on the annealed perovskite light absorption layer still with reactive activity, so that the Anchor group of DCL quickly coordinates with the surface defects of perovskite; then annealing at 100-110°C to promote DCL to penetrate deeper into the perovskite grain boundary, achieve bulk passivation, and the Crosslinker group undergoes polymerization reaction to form a dense, stable, insoluble three-dimensional cross-linked network on the surface of perovskite.

[0045] Preferably, the mild anti-solvent is selected from isopropanol or chlorobenzene.

[0046] In some specific embodiments, the DCL prepared by the present invention (taking 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid as an example) is dissolved in isopropanol at room temperature to prepare a DCL passivation solution with a concentration of 0.5 mg / mL. After the perovskite light-absorbing layer is prepared and annealed, while it is still warm, the DCL passivation solution is spin-coated at 4000 rpm for 30 seconds. During the spin-coating process, the solvent evaporates rapidly, and the DCL self-assembles on the perovskite surface and undergoes preliminary anchoring. Subsequently, the sample is placed on a hot plate at 100°C for annealing for 10 minutes. This heat treatment process promotes in-situ crosslinking polymerization of the trifluorovinyl ether groups in the DCL to form a stable network structure, and also completely removes the residual isopropanol solvent.

[0047] Preferably, the DCL passivation solution is spin-coated onto a perovskite light-absorbing layer at 90-120°C.

[0048] Preferably, the perovskite light-absorbing layer is a perovskite light-absorbing layer based on the CsPbI2Br system or the FAPbI3 system.

[0049] Preferably, the transparent conductive substrate is ITO conductive glass or FTO conductive glass; the electron transport layer is a fullerene derivative (PCBM) or SnO2; the hole transport layer is nickel oxide (NiOx) with a thickness of 10-15 nm; and the metal electrode is silver, gold, or aluminum with a thickness of 90-110 nm.

[0050] This invention relates to a perovskite solar cell based on a cross-linked interface passivation layer, which has a cross-linked interface passivation layer and phosphate anchoring groups that strongly passivate the interface Pb. 2+ The defects are overcome by using phenoxazine π-bridges to passivate halogen vacancies and promote hole transport, while the trifluorovinyl ether crosslinking network locks the passivated molecules, preventing migration and volatilization, and providing a strong hydrophobic barrier. The synergistic effect achieves comprehensive performance improvement, surpassing the simple effect of single-function additives.

[0051] The cross-linked interface passivation layer of the present invention differs from the pre-prepared polymer coating. The DCL first penetrates and anchors in the form of small molecules, and then cross-links into a network. This "penetration first, fixation later" strategy ensures that the passivating agent has sufficient contact with the defects and ultimately forms a stable interface layer that conformally and tightly binds to the perovskite surface, significantly reducing the interface recombination rate.

[0052] The cross-linked interface passivation layer of the present invention can significantly improve photovoltaic performance and stability, and the cross-linked network greatly enhances the intrinsic stability of the device. In the dual 85 aging test at 85°C / 85%RH, the time required for the device efficiency to decay to 80% of the initial value can exceed 1000 hours. Attached Figure Description

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort.

[0054] Figure 1 J-V curve diagram of the CsPbI2Br system perovskite solar cell of Examples 1-3 and Comparative Examples 1-5;

[0055] Figure 2 J-V curve diagram of the FAPbI3 system perovskite solar cell of Example 4 and Comparative Examples 6-10. DETAILED DESCRIPTION

[0056] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments in the present application without any creative effort are within the scope of protection of the present application.

[0058] Example 1:

[0059] The perovskite solar cell structure of the present embodiment is sequentially from bottom to top: transparent conductive substrate, electron transport layer, perovskite light absorption layer, cross-linked interface passivation layer, hole transport layer, metal electrode; and the preparation method is as follows.

[0060] Step 1: substrate pretreatment

[0061] The transparent conductive substrate (FTO-coated conductive glass) is sequentially ultrasonically cleaned with cleaning agent, deionized water, acetone and isopropanol, then dried with nitrogen, and finally treated with ultraviolet ozone for 15 minutes.

[0062] Step 2: depositing the electron transport layer

[0063] SnO2 colloid solution is prepared by sol-gel method and is spin-coated on the FTO substrate, and is annealed at 150°C for 30 minutes to form a dense electron transport layer.

[0064] Step 3: Preparation of CsPbI2Br perovskite light absorption layer

[0065] Lead iodide, lead bromide, cesium iodide and DMSO were prepared into a CsPbI2Br precursor solution in a ratio of 0.5 mol: 0.5 mol: 1.1 mol: 1 L; the precursor solution was spin-coated on the electron transport layer, specifically: first spin at 1000 rpm for 10 seconds, then spin at 4000 rpm for 30 seconds;

[0066] Chlorobenzene was added as an anti-solvent in the last 10 seconds before the end of spin coating; then, the film was annealed on a hot stage at 100°C for 5 minutes, and immediately transferred to a hot stage at 180°C for 10 minutes of annealing, to form the CsPbI2Br perovskite light absorption layer.

[0067] Step 4: Deposition of DCL interface passivation layer

[0068] 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]benzenephosphonic acid was dissolved in anhydrous isopropanol to prepare a DCL passivation solution with a concentration of 0.5 mg / mL; the DCL passivation solution was spin-coated on the CsPbI2Br film after 180°C high-temperature annealing (temperature reduced to 120-110°C), with parameters of 4000 rpm for 30 seconds; then, the sample was placed on a hot stage at 100°C for 10 minutes of annealing, to allow 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]benzenephosphonic acid to anchor and crosslink on the perovskite surface, forming a crosslinked interface passivation layer.

[0069] Step 5: Deposition of hole transport layer

[0070] A layer of nickel oxide film was spin-coated on the perovskite light absorption layer and annealed at 120°C for 20 min as a hole transport layer (thickness about 10 nm).

[0071] Step 6: Preparation of metal electrode

[0072] The sample was transferred to a vacuum evaporation device, and 90 nm of silver was evaporated as a metal electrode under a vacuum degree of less than 5×10 -4 Pa.

[0073] Example 2:

[0074] The perovskite solar cell structure of this example is from bottom to top: transparent conductive substrate, electron transport layer, perovskite light absorption layer, crosslinked interface passivation layer, hole transport layer, metal electrode; the preparation method is as follows.

[0075] Step 1: Substrate pretreatment

[0076] The transparent conductive substrate (FTO-coated conductive glass) was sequentially cleaned with cleaning agent, deionized water, acetone, isopropanol, and then dried with nitrogen, and finally treated with ultraviolet ozone for 15 minutes.

[0077] Step 2: Depositing an electron transport layer

[0078] A fullerene derivative (PCBM) was dissolved in chlorobenzene at a concentration of 21 mg / mL, spin-coated on the FTO substrate at 2400 rpm for 30 seconds, and then annealed at 50°C for 5 min to form an electron transport layer.

[0079] Step 3: Preparing a CsPbI2Br perovskite light absorption layer

[0080] Lead iodide, lead bromide, cesium iodide, and DMSO were prepared into a CsPbI2Br precursor solution in a ratio of 0.6 mol:0.6 mol:1.2 mol:0.9 L; the precursor solution was spin-coated on the electron transport layer, specifically: first spin at 1000 rpm for 10 seconds, then spin at 4000 rpm for 30 seconds;

[0081] At the last 10 seconds before the end of spin coating, chlorobenzene was added as an anti-solvent; then, the film was annealed on a hot stage at 100°C for 5 minutes, and immediately transferred to a hot stage at 180°C for 10 minutes to form a CsPbI2Br perovskite light absorption layer.

[0082] Step 4: Depositing a DCL interface passivation layer

[0083] 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]benzenephosphonic acid was dissolved in chlorobenzene to prepare a DCL passivation solution with a concentration of 0.4 mg / mL; the DCL passivation solution was spin-coated on the CsPbI2Br film after high-temperature 180°C annealing (temperature reduced to 120-110°C) with parameters of 4000 rpm for 30 seconds; then, the sample was annealed on a hot stage at 110°C for 10 minutes to allow 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]benzenephosphonic acid to anchor and crosslink on the perovskite surface, forming a crosslinked interface passivation layer.

[0084] Step 5: Depositing a hole transport layer

[0085] A layer of nickel oxide film was spin-coated on the perovskite light absorption layer and annealed at 120°C for 20 min as a hole transport layer (thickness about 15 nm).

[0086] Step 6: Preparing a metal electrode

[0087] The sample was transferred to a vacuum evaporation device, and a layer of gold was evaporated on the hole transport layer at a pressure below 5×10-4 Under the vacuum degree of Pa, 100nm of silver was evaporated as a metal electrode.

[0088] Example 3:

[0089] The perovskite solar cell structure of the present example is sequentially from bottom to top: a transparent conductive substrate, an electron transport layer, a perovskite light absorption layer, a cross-linked interface passivation layer, a hole transport layer, and a metal electrode. The preparation method is as follows.

[0090] Step 1: substrate pretreatment

[0091] The transparent conductive substrate (FTO-coated conductive glass) was sequentially cleaned with cleaning agent, deionized water, acetone, and isopropanol under ultrasonic cleaning, then dried with nitrogen, and finally treated with ultraviolet ozone for 15 minutes.

[0092] Step 2: depositing an electron transport layer

[0093] A SnO2 colloid solution was prepared by sol-gel method and spin-coated on the FTO substrate, and then annealed at 150℃ for 30 minutes to form a dense electron transport layer.

[0094] Step 3: preparing a CsPbI2Br perovskite light absorption layer

[0095] Lead iodide, lead bromide, cesium iodide, and DMSO were prepared into a CsPbI2Br precursor solution in a ratio of 0.55mol:0.55mol:1.15mol:1L; the precursor solution was spin-coated on the electron transport layer, specifically: first spin at 1000rpm for 10 seconds, then spin at 4000rpm for 30 seconds.

[0096] Chlorobenzene was added as an anti-solvent in the last 10 seconds before the end of spin coating; then the film was annealed on a hot stage at 110℃ for 5 minutes, and immediately transferred to a hot stage at 160℃ for 10 minutes to form a CsPbI2Br perovskite light absorption layer.

[0097] Step 4: depositing a DCL interface passivation layer

[0098] 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid was dissolved in anhydrous isopropanol to prepare a DCL passivation solution with a concentration of 0.6 mg / mL; the DCL passivation solution was spin-coated on the CsPbI2Br thin film after high-temperature 160°C annealing (temperature was reduced to 120-110°C) with the parameters of 4000 rpm for 30 seconds; then, the sample was placed on a hot stage at 105°C for 10 minutes to anneal, so that 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid was anchored and cross-linked on the perovskite surface to form a cross-linked interfacial passivation layer.

[0099] Step 5: deposition of hole transport layer

[0100] A layer of nickel oxide film was spin-coated on the perovskite light absorption layer and annealed at 120°C for 20 min as a hole transport layer (thickness about 10 nm).

[0101] Step 6: preparation of metal electrode

[0102] The sample was transferred to a vacuum evaporation device, and 110 nm of silver was evaporated as a metal electrode under a vacuum degree of less than 5×10 -4 Pa.

[0103] Comparative Example 1

[0104] The perovskite solar cell of the present comparative example is different from Example 1 in that step 4 (i.e., no DCL interfacial passivation layer) is not included, and other steps are the same as Example 1.

[0105] Comparative Example 2

[0106] The perovskite solar cell of the present comparative example is different from Example 1 in that in step 4, the concentration of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid in the DCL passivation solution is 0.3 mg / mL, and other steps are the same as Example 1.

[0107] Comparative Example 3

[0108] The perovskite solar cell of the present comparative example is different from Example 1 in that in step 4, the concentration of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid in the DCL passivation solution is 0.8 mg / mL, and other steps are the same as Example 1.

[0109] Comparative Example 4

[0110] The perovskite solar cell of the present comparative example differs from Example 1 in that in Step 4, the annealing temperature is 80°C, and other steps are the same as Example 1.

[0111] Comparative Example 5

[0112] The perovskite solar cell of the present comparative example differs from Example 1 in that in Step 4, the annealing temperature is 130°C, and other steps are the same as Example 1.

[0113] The CsPbI2Br system perovskite solar cells of Examples 1-3 and Comparative Examples 1-5 above were tested for photoelectric performance and stability. The photoelectric performance test was determined under standard AM 1.5G simulated sunlight, light intensity 100 mw / cm 2 , and the effective light area was 0.09 cm 2 . The current density-voltage curve was collected using a Keithley 2400 source meter. The stability test was carried out in an unsealed state, the device was placed in a constant temperature and humidity chamber, and continuously aged at a temperature of 85°C and a relative humidity of 85%, and periodically removed for measurement of the efficiency retention rate. The results are shown in Table 1 below:

[0114] Table 1 Photoelectric performance and stability test results of Examples 1-3 and Comparative Examples 1-5

[0115]

[0116] The J-V curves of the CsPbI2Br system perovskite solar cells of Examples 1-3 and Comparative Examples 1-5 are shown in Figure 1 .

[0117] From the test results in Table 1, it can be seen that:

[0118] In terms of photoelectric performance, the photoelectric conversion efficiency, open circuit voltage and fill factor of all Examples 1-3 containing the DCL interface passivation layer of the present application were significantly higher than those of Comparative Example 1 (without DCL layer), indicating the key role of DCL in improving device performance; the comprehensive performance of Example 1 (concentration 0.5 mg / mL, annealing 100°C) was the best, indicating that this was the best process under the system; Comparative Examples 2-3 showed that too low or too high DCL concentration would lead to performance decline, too low concentration would not be sufficient for passivation and crosslinking, and too high concentration would form an excessively thick insulating layer to hinder charge transport; Comparative Examples 4-5 showed that annealing temperature was crucial to crosslinking effect, too low temperature would lead to incomplete crosslinking reaction, and too high temperature would possibly damage the interface or perovskite layer.

[0119] In terms of stability, the devices of Examples 1-3 exhibited extremely excellent stability in the accelerated aging test at 85°C / 85%RH, with T80 lifetime close to or even exceeding 1000 hours, significantly better than all the comparative examples; the stability of Comparative Example 1 (without DCL) was the worst, with T80 lifetime of only 350 hours, highlighting the decisive role of the DCL cross-linked network in blocking water and oxygen, inhibiting ion migration and fixing the interface; the stability of Comparative Examples 2-5 was between Examples and Comparative Example 1, but none of them reached the best effect, indicating that appropriate DCL concentration and sufficient cross-linking reaction are necessary conditions for obtaining high stability.

[0120] Example 4

[0121] The preparation method of the perovskite solar cell of the present example is different from steps 3 and 4 of Example 1.

[0122] Specifically, FAPbI3 perovskite light absorption layer is used in step 3 of the present example to replace the CsPbI2Br perovskite light absorption layer in Example 1; the preparation of the FAPbI3 perovskite light absorption layer in the present example is as follows: lead iodide (1.2 mol), formamidinium iodide (0.83 mol), methylammonium iodide (0.1 mol), lead bromide (0.21 mol) and methylammonium chloride (1.2 mol) are dissolved in 1L of DMF:DMSO (4:1, v / v) mixed solvent, stirred at 60°C until completely dissolved, filtered after cooling, and the perovskite precursor solution is obtained; spin-coat the precursor solution on the electron transport layer, the specific procedure is: 1000 rpm for 10 seconds, then 5000 rpm for 30 seconds, and drop 20 seconds before the end of the second step chlorobenzene as anti-solvent; then, the film is placed on a hot stage at 100°C for annealing for 60 minutes to form the FAPbI3-based perovskite light absorption layer;

[0123] The specific operation of depositing the DCL interface passivation layer in step 4 of the present example is as follows: 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid is dissolved in anhydrous isopropanol to prepare a DCL passivation solution with a concentration of 0.5 mg / mL; spin-coat the DCL passivation solution on the FAPbI3 film (90-100°C) immediately after annealing, with parameters of 4000 rpm for 30 seconds; then, the sample is placed on a hot stage at 100°C for annealing for 10 minutes, so that 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid is anchored and cross-linked on the perovskite surface to form a cross-linked interface passivation layer;

[0124] The other steps are the same as Example 1.

[0125] Comparative Example 6

[0126] The perovskite solar cell of the present comparative example is different from example 4 in that step 4 (i.e. DCL interface passivation layer is not included), and other steps are the same as example 4.

[0127] Comparative example 7

[0128] The perovskite solar cell of the present comparative example is different from example 4 in that in step 4, the concentration of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid in the DCL passivation solution is 0.3 mg / mL, and other steps are the same as example 4.

[0129] Comparative example 8

[0130] The perovskite solar cell of the present comparative example is different from example 4 in that in step 4, the concentration of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]benzenephosphonic acid in the DCL passivation solution is 0.8 mg / mL, and other steps are the same as example 4.

[0131] Comparative example 9

[0132] The perovskite solar cell of the present comparative example is different from example 4 in that in step 4, the annealing temperature is 80°C, and other steps are the same as example 4.

[0133] Comparative example 10

[0134] The perovskite solar cell of the present comparative example is different from example 4 in that in step 4, the annealing temperature is 130°C, and other steps are the same as example 4.

[0135] The FAPbI3 system perovskite solar cells of example 4 and comparative examples 6-10 are tested for photoelectric performance and stability by using the same photoelectric performance and stability test methods as described above, and the results are shown in Table 2 below:

[0136] Table 2 Photoelectric performance and stability test results of example 4 and comparative examples 6-10

[0137]

[0138] The J-V curves of the FAPbI3 system perovskite solar cells of example 4 and comparative examples 6-10 are shown in Figure 2

[0139] From the test results in Table 2, it can be seen that:

[0140] ​In terms of photoelectric performance, the embodiment 4 (FAPbI3 system + DCL modification) obtained an excellent efficiency of 24.85%, which was significantly higher than all the comparative examples, proving the key role of DCL in the high-efficiency FAPbI3 system; compared with comparative example 6 (without DCL), the Voc and FF of embodiment 4 were most obviously improved, which reflected the excellent effect of DCL in defect passivation and interface optimization; comparative examples 7-8 showed that the influence of DCL concentration on performance was consistent with the trend of the CsPbI2Br system, and 0.5 mg / mL was the best concentration. Comparative examples 9-10 proved that 100℃ was the best temperature for DCL crosslinking, and too low temperature would not completely crosslink, and too high temperature might affect the performance of the perovskite layer.

[0141] In terms of stability, embodiment 4 exhibited a T80 lifetime of more than 1000 hours under the condition of 85℃ / 85%RH, which showed the perfect compatibility and excellent stability of the FAPbI3 system and the DCL interface layer; the T80 lifetime of comparative example 6 (without DCL) was only 420 hours, which highlighted the irreplaceable role of the DCL crosslinking network in protecting the FAPbI3 film, inhibiting phase separation and degradation; the stability of all comparative examples containing DCL (7-10) was better than that of comparative example 6, but did not reach the level of embodiment 4.

[0142] In summary, the above test results fully proved that the crosslinked interface passivation layer provided by the present application could synergistically improve the photoelectric conversion efficiency and long-term working stability of perovskite solar cells, and solved the key technical problems in this field.

[0143] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A perovskite solar cell based on a cross-linked interface passivation layer, characterized in that, From bottom to top: transparent conductive substrate, electron transport layer, perovskite light absorption layer, cross-linked interface passivation layer, hole transport layer, and metal electrode; The cross-linked interface passivation layer is 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid material; The structural formula of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid is as follows (I): Formula (I); The preparation of the cross-linked interface passivation layer includes the following steps: 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid is dissolved in a mild antisolvent to prepare a DCL passivation solution, which is then spin-coated onto the annealed perovskite light-absorbing layer that is still reactive, and then annealed at 100-110°C; The concentration of 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazine-2-yl]phenylphosphonic acid in the DCL passivation solution is 0.4-0.6 mg / mL; The perovskite light-absorbing layer is a perovskite light-absorbing layer based on the CsPbI2Br system or the FAPbI3 system.

2. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1, characterized in that, The mild antisolvent is selected from isopropanol or chlorobenzene.

3. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1, characterized in that, The preparation of the cross-linked interface passivation layer includes the following steps: 4-[10-(4-{(1,2,2-trifluorovinyl)oxy}phenyl)-10H-phenoxazin-2-yl]phenylphosphonic acid was dissolved in isopropanol at room temperature to prepare a DCL passivation solution with a concentration of 0.5 mg / mL. The DCL passivation solution was spin-coated onto the annealed and still reactive perovskite light-absorbing layer at a speed of 4000 rpm for 30 seconds, and then annealed on a hot plate at 100°C for 10 minutes.

4. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1 or 3, characterized in that, The DCL passivation solution is spin-coated onto a perovskite light-absorbing layer at 90-120℃.

5. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1, characterized in that, The electron transport layer is a fullerene derivative or SnO2.

6. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1, characterized in that, The hole transport layer is a nickel oxide layer with a thickness of 10–15 nm.

7. The perovskite solar cell based on a cross-linked interface passivation layer according to claim 1, characterized in that, The transparent conductive substrate is ITO conductive glass or FTO conductive glass; the metal electrode is silver, gold or aluminum, with a thickness of 90-110 nm.

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