Perovskite solar cell passivating grain boundary defects and preparation method thereof

Abstract

The application discloses a perovskite solar cell passivating grain boundary defects and a preparation method thereof, and the cell is composed of a conductive substrate layer, a hole transport layer, a polyethylene oxide passivated perovskite light absorption layer, an electron transport layer, a buffer layer and a silver electrode in sequence; the preparation method comprises the following steps: (1) selecting ITO as the conductive substrate, and preparing the hole transport layer on the substrate; (2) spin-coating a perovskite precursor solution, adopting a chlorobenzene solution of polyethylene oxide as an anti-solvent to treat a perovskite wet film in a spin-coating process, then annealing treatment is conducted again to form the polyethylene oxide passivated perovskite light absorption layer; and (3) sequentially preparing the electron transport layer and the buffer layer, and finally evaporating the silver electrode; the cell treats the perovskite wet film by PEO, reduces the formation of grain boundary defects of the perovskite thin film, improves the charge transport efficiency, inhibits non-radiative recombination, and makes the open-circuit voltage, the short-circuit current and the fill factor of the device all improved, and the stability of the cell is further improved.

Description

Technical Field

[0001] This invention relates to a perovskite solar cell, and more particularly to a perovskite solar cell with passivated grain boundary defects and its fabrication method. Background Technology

[0002] In a perovskite solar cell structure, when light enters from the conductive glass side, it passes through the charge transport layer and reaches the perovskite light-absorbing layer. The perovskite absorbs the light, generating photogenerated electron-hole pairs, which then dissociate into electrons and holes. These electrons and holes are transferred to the electron transport layer and hole transport layer, respectively. When the external circuit is connected to the anode and cathode of the solar cell to form a closed loop, a current is generated. The solar cell converts light energy into electrical energy through the photoelectric effect. Organic-inorganic halide perovskites have shown great potential in optoelectronic devices due to their excellent photoelectric properties, solution-processable nature, and low cost. The photoelectric conversion efficiency of perovskite solar cells has increased from 3.8% in 2009 to the current 25.8%, which is comparable to that of monocrystalline silicon solar cells.

[0003] However, perovskite films prepared at low temperatures exhibit numerous defects on their surface and at grain boundaries, which severely impacts the improvement of open-circuit voltage, short-circuit current, and fill factor in perovskite solar cells. Furthermore, these defects provide pathways for ion migration, exacerbating the hysteresis effect and hindering the improvement of long-term stability of perovskite solar cells. Summary of the Invention

[0004] Objective of the invention: The present invention aims to provide a perovskite solar cell with passivated grain boundary defects that reduces the formation of grain boundary defects in perovskite thin films and improves the photoelectric conversion efficiency and stability of perovskite solar cells; another objective of the present invention is to provide a method for preparing the perovskite solar cell.

[0005] Technical solution: The perovskite solar cell with passivated grain boundary defects of the present invention is composed of a conductive substrate layer, a hole transport layer, a perovskite light-absorbing layer passivated with polyethylene oxide (PEO), an electron transport layer, a buffer layer, and a silver electrode, forming an inverted structure; wherein the perovskite light-absorbing layer passivated with polyethylene oxide is formed by treating the perovskite wet film with a polyethylene oxide chlorobenzene solution as an antisolvent, and the ether bonds and hydroxyl groups in polyethylene oxide crosslink with the perovskite, and then annealing treatment.

[0006] The hole transport layer is used to increase the number of holes and extract effective charge; the PEO-passivated perovskite light-absorbing layer generates electron-hole pairs under illumination and separates them at the perovskite interface. The defect states of the perovskite film after PEO passivation are reduced, effectively reducing non-radiative recombination and improving charge transport efficiency, thereby improving device performance; the electron transport layer is used to transport electrons, allowing more electrons to be transported to the silver electrode; the buffer layer is used to hinder hole transport to the silver electrode and reduce damage to the perovskite film during metal evaporation; the external circuit connects the silver electrode and the conductive substrate, forming a closed loop to generate current.

[0007] Preferably, the concentration of the polyethylene oxide chlorobenzene solution is 0.2–0.4 mg / mL.

[0008] Preferably, the perovskite wet film is MAPbI3.

[0009] Preferably, the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA).

[0010] Preferably, the electron transport layer is 6,6-phenyl-C 61 methyl butyrate (PC) 61 BM).

[0011] Preferably, the buffer layer is 4,7-diphenyl-o-phenanthroline (Bphen).

[0012] The method for preparing a perovskite solar cell according to the present invention includes the following steps:

[0013] (1) ITO was selected as the conductive substrate, and a hole transport layer was prepared on the substrate;

[0014] (2) Spin-coating perovskite precursor solution. During the spin-coating process, chlorobenzene solution of polyethylene oxide is used as an anti-solvent to treat the perovskite wet film, and then annealing is performed to form a perovskite light-absorbing layer passivated by polyethylene oxide.

[0015] (3) An electron transport layer and a buffer layer are prepared sequentially, and finally a silver electrode is deposited to obtain a perovskite solar cell with passivated grain boundary defects.

[0016] In step (1), the ITO conductive substrate also includes a cleaning process, in which glass cleaner, deionized water, acetone and anhydrous ethanol are used in sequence for ultrasonic cleaning for 20 minutes. This is mainly to remove dust and organic and inorganic impurities from the conductive substrate, which is beneficial to the formation of high-quality thin films in the later stage.

[0017] The specific method for preparing the hole transport layer (HTL) is as follows: PTAA solution is spin-coated onto an ITO substrate, followed by annealing to form the hole transport layer. Preferably, the spin-coating speed of the PTAA solution is 4000–4500 rpm, and the spin-coating time is 30–35 seconds; then, the HTL is formed after annealing at 105°C for 10 minutes.

[0018] Preferably, in step (1), the preparation of the hole transport layer further includes treating the hole transport layer with N,N-dimethylformamide and toluene; the spin coating speed of the DMF solution is 3500-4000 rpm, the spin coating time is 30-35 seconds, and toluene solution is added dropwise at the 20th-25th second after the start of spin coating to form HTL with good wettability.

[0019] Preferably, in step (2), the spin-coated perovskite precursor solution is first spin-coated at a speed of 800-1000 rpm for 15-20 seconds; then spin-coated at a speed of 4500-5000 rpm for 25-30 seconds, during which a chlorobenzene solution containing polyethylene oxide is added dropwise. Preferably, in step (2), the annealing temperature is 90-100°C, and the time is 10-20 minutes.

[0020] Preparation of perovskite solution: Weigh 198.7 mg MAI and 576 mg PbI2 powder into a brown bottle using a balance, add 1 mL of DMF solution, place the perovskite solution in a glove box and heat and stir at 70 °C for 12 hours, then filter with a 0.45 μm organic filter to obtain the perovskite precursor solution.

[0021] The electron transport layer (ETL) is specifically prepared by spin-coating 6,6-phenyl-C 61 A chlorobenzene solution of methyl butyrate forms an electron transport layer.

[0022] The buffer layer is specifically prepared by spin-coating an ethanol solution of 4,7-diphenyl-o-phenanthroline (Bphen) followed by annealing to form the buffer layer.

[0023] Invention Mechanism: The battery of this invention has an inverted structure. Its working mechanism is that when the perovskite light-absorbing layer is exposed to light, excitons are generated. The excitons dissociate into electrons and holes at the interface between the electron transport layer and the hole transport layer. Then, the electrons are transported from the conduction band of the perovskite to the LUMO level of the electron transport layer, and the holes are transported from the valence band of the perovskite to the HOMO level of the hole transport layer, and then further transported to the silver electrode and the conductive substrate, respectively. Compared with the upright perovskite solar cell, the electron transport layer used in the inverted structure battery is an organofullerene derivative ([6,6]-phenyl-C) that can be left unannealed. 61 methyl butyrate, PC 61The inverted perovskite solar cell avoids the high-temperature processing required in the upright structure. Furthermore, the hole transport layer is changed from the hygroscopic 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (spiro-OMeTAD) in the upright structure to poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) in the inverted structure, improving device stability. The simple fabrication process and high stability of the inverted perovskite solar cell offer significant advantages.

[0024] In this invention, polyethylene oxide (PEO) is added to the antisolvent chlorobenzene solution. During the 3rd to 5th second of spin-coating the perovskite precursor solution at a rotation speed of 4500–5000 rpm, the chlorobenzene solution containing PEO is added dropwise (at this point, the perovskite is a wet film). The PEO in the antisolvent crosslinks with the wet perovskite film. The unique ductility of the PEO polymer reduces the formation of perovskite grain boundary defects, regulates the growth of the perovskite film, effectively promotes charge transport, and reduces non-radiative recombination losses, thereby improving the performance of the inverted structure battery. After optimal treatment with 0.2 mg / mL PEO, the grain size of the perovskite film decreases, but the root mean square roughness of the perovskite film surface decreases, which is beneficial for improving the interfacial contact between the perovskite and the electron transport layer, thus improving charge transport efficiency. This is consistent with the quenching effect of steady-state fluorescence and the phenomenon of reduced carrier lifetime. Further research revealed that the ether bonds and hydroxyl groups in the PEO molecule can interact with perovskite, thereby passivating defects at the grain boundaries of the perovskite film, suppressing nonradiative recombination and ion migration, resulting in a significant increase in the open-circuit voltage and suppression of hysteresis effects. Furthermore, the reduction in defects and suppression of ion migration in the perovskite film effectively improves the stability of the device.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The battery is an inverted structure. By adding passivating agent PEO to the antisolvent to treat the perovskite wet film, the growth of the perovskite film is regulated, the formation of grain boundary defects of the perovskite film is reduced, the film becomes smoother, the charge transport efficiency is improved, and non-radiative recombination is suppressed, which improves the open circuit voltage, short circuit current and fill factor of the device, and the stability of the battery is further improved; (2) When the PEO concentration is 0.2 mg / mL, the photoelectric conversion efficiency (PCE) of the inverted perovskite solar cell is 19.35%, the hysteresis factor is 0.031, and after being stored in a nitrogen environment for 1000 hours, the photoelectric conversion efficiency of the battery can still maintain 97% of the initial photoelectric conversion efficiency; (3) The passivation strategy in this preparation method does not require the addition of other processes, which reduces the preparation cost and is simple and efficient. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the inverted battery of the present invention;

[0027] Figure 2 SEM and AFM images of the perovskite films prepared in Example 1 and Comparative Example 1;

[0028] Figure 3 X-ray photoelectron spectroscopy (XPS) spectra of the perovskite thin films prepared in Example 1 and Comparative Example 1;

[0029] Figure 4 Steady-state fluorescence PL spectra of the perovskite films prepared in Example 1 and Comparative Example 1;

[0030] Figure 5 Time-resolved photoluminescence (TRPL) spectra of the perovskite thin films prepared in Example 1 and Comparative Example 1;

[0031] Figure 6 Current density-voltage (JV) curves of the pure hole devices prepared in Example 1 and Comparative Example 1 under dark conditions;

[0032] Figure 7 The current density-voltage (JV) curves of the perovskite solar cells prepared in Examples 1-3 and Comparative Example 1 are shown.

[0033] Figure 8 The hysteresis effect is shown in the JV curves of the perovskite solar cells prepared in Example 1 and Comparative Example 1.

[0034] Figure 9 The graph shows the stability test results of the perovskite solar cells prepared in Example 1 and Comparative Example 1 under a nitrogen atmosphere. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the embodiments.

[0036] Example 1

[0037] The perovskite solar cell with passivated grain boundary defects of the present invention is prepared by the following steps:

[0038] (1) The ITO conductive substrate was ultrasonically cleaned in glass cleaner, deionized water, acetone and anhydrous ethanol for 20 minutes in sequence. Then the cleaned ITO substrate was placed in a drying oven to dry. Finally, it was treated with ultraviolet ozone to improve the wettability of the substrate.

[0039] (2) On a clean ITO substrate, spin-coat PTAA solvent at a speed of 4000 rpm for 30 seconds. After spin-coating, anneal at 105°C for 10 minutes to form HTL.

[0040] (3) On PTAA, DMF is spread all over the substrate, and then spin-coated at 3500 rpm for 30 seconds. 50 μL of toluene is added 20 seconds after the spin-coating begins to form HTL with good wetting properties.

[0041] (4) On the modified PTAA substrate, the MAPbI3 perovskite precursor solution was first spin-coated at 800 rpm for 15 seconds, and then at 4500 rpm for 25 seconds. At the third second after the second spin-coating, 150 μL of 0.2 mg / mL PEO chlorobenzene solution as an antisolvent was dropped into the center of the perovskite wet film. Then it was placed on a hot table at 100 °C for annealing for 15 minutes. The perovskite film changed from reddish-brown to black, forming a PEO passivated perovskite light-absorbing layer.

[0042] (5) On the perovskite film, 20 mg / mL of PC was applied. 61 BM chlorobenzene solution was spin-coated at 3000 rpm for 30 seconds to form an ETL layer;

[0043] (6) On the ETL layer, spin-coat 40 μL of 4,7-diphenyl-o-phenanthroline (Bphen) solution at 6500 rpm for 45 seconds. After spin-coating, anneal at 60°C for 10 minutes to form a buffer layer.

[0044] (7) An Ag electrode of approximately 100 nm thickness was deposited on the buffer layer using a vacuum thermal evaporation apparatus. The entire inverted device structure is composed of ITO / PTAA / Perovskite / PC. 61 The preparation of BM / Bphen / Ag is complete.

[0045] The required chemical materials include: methylamine iodide (99.5%, MAI), lead iodide (99.999%, PbI2), N,N-dimethylformamide (99.9%, DMF), chlorobenzene (99.999%, CB), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 6,6-phenyl C 61 Methyl butyrate (PC) 61 BM), 4,7-diphenyl-1,10-phenanthroline (Bphen), polyethylene oxide (PEO), ITO conductive substrate, Ag metal particles.

[0046] Preparation of perovskite precursor solution: Weigh 198.7 mg MAI and 576 mg PbI2 powder into a brown bottle using a balance, add 1 mL of DMF solution, mix well, place the mixture in a glove box and heat and stir at 70 °C for 12 hours, and then filter with a 0.45 μm organic filter.

[0047] Preparation of PEO passivating agent: Dissolve 12 mg of PEO powder in 10 mL of chlorobenzene to form a 1.2 mg / mL PEO chlorobenzene solution, and then dilute it to 0.2 mg / mL, 0.3 mg / mL, and 0.4 mg / mL.

[0048] Example 2

[0049] The perovskite solar cell with passivated grain boundary defects of the present invention is prepared by the following steps:

[0050] (1) The ITO conductive substrate was ultrasonically cleaned in glass cleaner, deionized water, acetone and anhydrous ethanol for 20 minutes in sequence. Then the cleaned ITO substrate was placed in a drying oven to dry. Finally, it was treated with ultraviolet ozone to improve the wettability of the substrate.

[0051] (2) On a clean ITO substrate, spin-coat PTAA solvent at a speed of 4000 rpm for 30 seconds. After spin-coating, anneal at 105°C for 10 minutes to form HTL.

[0052] (3) On PTAA, DMF is spread all over the substrate, and then spin-coated at 3500 rpm for 30 seconds. 50 μL of toluene is added 20 seconds after the spin-coating begins to form HTL with good wetting properties.

[0053] (4) On the modified PTAA substrate, the MAPbI3 perovskite solution was first spin-coated at 800 rpm for 15 seconds, and then at 4500 rpm for 25 seconds. At the third second after the second spin-coating, 150 μL of 0.3 mg / mL PEO chlorobenzene solution as an antisolvent was dropped into the center of the perovskite wet film. Then it was placed on a hot table at 100 °C for annealing for 15 minutes. The perovskite film changed from reddish-brown to black, forming a perovskite light-absorbing layer.

[0054] (5) On the perovskite film, 20 mg / mL of PC was applied. 61 BM chlorobenzene solution was spin-coated at 3000 rpm for 30 seconds to form an ETL layer;

[0055] (6) On the ETL layer, spin-coat 40 μL of 4,7-diphenyl-o-phenanthroline (Bphen) solution at 6500 rpm for 45 seconds. After spin-coating, anneal at 60°C for 10 minutes to form a buffer layer.

[0056] (7) An Ag electrode of approximately 100 nm thickness was deposited on the buffer layer using a vacuum thermal evaporation apparatus. The entire inverted device structure is composed of ITO / PTAA / Perovskite / PC. 61 The preparation of BM / Bphen / Ag is complete.

[0057] Example 3

[0058] The perovskite solar cell of the present invention, which introduces PEO to passivate grain boundary defects, is prepared by the following steps:

[0059] (1) The ITO conductive substrate was ultrasonically cleaned in glass cleaner, deionized water, acetone and anhydrous ethanol for 20 minutes in sequence. Then the cleaned ITO substrate was placed in a drying oven to dry. Finally, it was treated with ultraviolet ozone to improve the wettability of the substrate.

[0060] (2) On a clean ITO substrate, spin-coat PTAA solvent at a speed of 4000 rpm for 30 seconds. After spin-coating, anneal at 105°C for 10 minutes to form HTL.

[0061] (3) On PTAA, DMF is spread all over the substrate, and then spin-coated at 3500 rpm for 30 seconds. 50 μL of toluene is added 20 seconds after the spin-coating begins to form HTL with good wetting properties.

[0062] (4) On the modified PTAA substrate, the MAPbI3 perovskite solution was first spin-coated at 800 rpm for 15 seconds, and then at 4500 rpm for 25 seconds. At the third second after the second spin-coating, 150 μL of 0.4 mg / mL PEO chlorobenzene solution as an antisolvent was dropped into the center of the perovskite wet film. Then it was placed on a hot table at 100 °C for annealing for 15 minutes. The perovskite film changed from reddish-brown to black, forming a PEO passivated perovskite light-absorbing layer.

[0063] (5) On the perovskite film, 20 mg / mL of PC was applied. 61 BM chlorobenzene solution was spin-coated at 3000 rpm for 30 seconds to form an ETL layer;

[0064] (6) On the ETL layer, spin-coat 40 μL of 4,7-diphenyl-o-phenanthroline (Bphen) solution at 6500 rpm for 45 seconds. After spin-coating, anneal at 60°C for 10 minutes to form a buffer layer.

[0065] (7) An Ag electrode of approximately 100 nm thickness was deposited on the buffer layer using a vacuum thermal evaporation apparatus. The entire inverted device structure is composed of ITO / PTAA / Perovskite / PC. 61 The preparation of BM / Bphen / Ag is complete.

[0066] Comparative Example 1

[0067] Based on Example 1, PEO was not added to the antisolvent chlorobenzene, and other conditions remained unchanged.

[0068] Performance testing

[0069] (1) SEM and AFM testing of perovskite thin films

[0070] Field emission scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed on the perovskite thin films in the perovskite solar cells of Example 1 and Comparative Example 1. The results are as follows: Figure 2 As shown.

[0071] from Figure 2 As can be observed in (ab), with the addition of PEO polymer, the grain size of the perovskite film is significantly reduced, and the perovskite film treated with PEO is more uniform and dense. Furthermore, PEO can be observed near the grain boundaries. Figure 2 As shown in (cd), the root mean square (RMS) surface roughness of the PEO-treated perovskite film is 10.8 nm, which is significantly smaller than that of the perovskite film without PEO passivation. This indicates that the perovskite film is smoother, which is beneficial for the interaction between perovskite and PC. 61 The interfacial contact between BMs promotes charge transport efficiency.

[0072] (2) X-ray photoelectron spectroscopy (XPS) testing of perovskite thin films

[0073] X-ray photoelectron spectroscopy (XPS) was performed on the perovskite films of Example 1 and Comparative Example 1 using a Thermo ESCALAB 250Xi to analyze the chemical state of the perovskite film surfaces with and without PEO passivation. The results are as follows: Figure 3 As shown.

[0074] from Figure 3 As can be observed in (a), a new peak appears in the O1s spectrum of the perovskite film after PEO passivation treatment. This new peak originates from oxygen atoms on the PEO, indicating that PEO was successfully introduced into the perovskite film. Figure 3 In (bc), it was found that under the passivation effect of PEO, the peak positions in the Pb 4f and I 3d spectra of the perovskite film shifted to lower energy levels. This is because the ether bonds and hydroxyl groups in PEO react with the perovskite, thereby reducing the defects in the perovskite film.

[0075] (3) Steady-state fluorescence intensity (PL) test of perovskite thin film

[0076] Steady-state fluorescence intensity of the perovskite films of Example 1 and Comparative Example 1 was measured using a 325 nm spectrometer under dark conditions. The test results are as follows: Figure 4 As shown.

[0077] from Figure 4It can be observed that the photoelectric potential (PL) intensity of the PEO-passivated perovskite film is significantly weaker than that of the unpassivated perovskite film, indicating that a quenching effect occurs in the perovskite film, suppressing nonradiative recombination and enabling rapid charge transport. Furthermore, the PPL of the PEO-passivated perovskite film exhibits a significant blue shift, suggesting that defects in the perovskite film are effectively passivated.

[0078] (4) Carrier lifetime test of perovskite thin film

[0079] Time-resolved photoluminescence (TRPL) tests were performed on the perovskite films of Example 1 and Comparative Example 1 under dark conditions using an Edinburgh FLS1000 spectrometer. The results are as follows: Figure 5 As shown.

[0080] from Figure 5 It can be observed that the time-resolved photoluminescence curves all conform to the double exponential decay equation:

[0081] f(t)=A1 exp(-t / τ1)+A2 exp(-t / τ2)+y0

[0082] Where τ1 is the rapid decay time, τ2 is the slow decay time, A1 and A2 are the corresponding relative amplitudes, and y0 is a constant. The average decay lifetime of the charge carriers (τ...) avg Calculate according to the following formula:

[0083]

[0084] The calculation results are shown in Table 1. Compared with the perovskite film without PEO treatment, the average carrier decay lifetime of the perovskite film treated with PEO decreased from 96.29 ns to 25.14 ns. The reduction in carrier lifetime is due to rapid charge transfer and defect passivation, which indicates that PEO treatment can significantly modulate the carrier dynamics of the perovskite film.

[0085] Table 1. Carrier lifetime parameters for TRPL curve fitting.

[0086]

[0087] (5) Current density-voltage (JV) curve test of pure hole device under dark conditions

[0088] The pure hole devices (ITO / PTAA / perovskite / PTAA / Ag) prepared from the perovskite thin films of Example 1 and Comparative Example 1 were tested for current density-voltage (JV) curves under dark conditions using an AAA-grade steady-state solar simulation testing system. The results are as follows: Figure 6 As shown. Defect state density (N) of perovskite thin films. trapThe following equation can be used for estimation:

[0089]

[0090] Where ε₀ is the vacuum permittivity, ε r V is the relative permittivity of the perovskite film. TFL The initial voltage for filling the trap-filling limit region, e is the fundamental charge, and L is the thickness of the perovskite layer. From Figure 6 It can be observed that the Vo of perovskite films passivated with PEO and those without PEO passivation... TFL The values ​​are 0.764V and 1.006V, respectively. According to the defect state density estimation formula, the defect state densities of the PEO-passivated perovskite film and the unpassivated perovskite film are 4.085 × 10⁻⁶ V and 1.006V, respectively. +15 cm -3 and 5.38×10 +15 cm -3 This indicates that PEO effectively passivates defects in perovskite films.

[0091] (6) Battery current density-voltage (JV) curve test

[0092] Using a AAA-grade steady-state solar simulation instrument (AM 1.5G, 100mW / cm²) 2 The testing system performed JV curve tests on the batteries of Examples 1-3 and Comparative Example 1. The test results are as follows: Figure 7 and Figure 8 As shown. JV curves of the device under different PEO chlorobenzene solution concentrations ( Figure 7 The photovoltaic parameters of the perovskite solar cells are shown in Table 2. It can be observed that adding only 0.2–0.4 mg / mL of PEO significantly improves the photoelectric conversion efficiency (PCO) of the perovskite solar cells. The device performance is optimal at a PEO concentration of 0.2 mg / mL, achieving a PCO efficiency of 19.35%, with the short-circuit current reaching its maximum value, and open-circuit voltage and fill factor showing significant improvements. When the PEO concentration exceeds 0.2 mg / mL, the short-circuit current begins to decrease, leading to a decrease in PCO efficiency. The improved device performance is mainly due to the passivation effect of PEO, which reduces the defect state density, suppresses non-radiative recombination, and accelerates charge transport.

[0093] Table 2. Photovoltaic parameters of JV curves of cells passivated with different concentrations of PEO chlorobenzene solution.

[0094]

[0095] Figure 8The graphs show the hysteresis JV curves under the same test conditions for forward and reverse scanning. The hysteresis effect of the device can be evaluated by the hysteresis factor (HI).

[0096]

[0097] Calculations revealed that the hysteresis factor of the unpassivated perovskite solar cell was 0.056, while that of the passivated cell was 0.031, indicating that the hysteresis effect of perovskite solar cells was significantly suppressed after PEO passivation. This is mainly because PEO passivates the defects in the perovskite film, blocking the channels for ion migration.

[0098] (7) Battery stability test

[0099] The unencapsulated batteries of Example 1 and Comparative Example 1 were subjected to stability tests under nitrogen atmosphere, and the results are as follows: Figure 9 As shown, PEO-passivated perovskite solar cells, after 1000 hours in a nitrogen atmosphere, retain 97% of their initial photoelectric conversion efficiency (PEP); while unpassivated perovskite solar cells only retain 86% of their initial PEP under the same conditions. According to literature, the stability of perovskite solar cells is affected not only by water and oxygen but also primarily by ion migration. Therefore, the improved stability of PEO-passivated perovskite solar cells in a nitrogen atmosphere mainly stems from the suppression of ion migration.

Claims

1. A perovskite solar cell with passivated grain boundary defects, characterized in that, It consists of a conductive substrate layer, a hole transport layer, a polyethylene oxide passivated perovskite light-absorbing layer, an electron transport layer, a buffer layer, and a silver electrode, forming an inverted structure. The polyethylene oxide passivated perovskite light-absorbing layer is formed by treating the perovskite wet film with polyethylene oxide chlorobenzene solution as an antisolvent, and the ether bonds and hydroxyl groups in polyethylene oxide crosslink with the perovskite, followed by annealing. The process of treating the perovskite wet film with a polyoxyethylene chlorobenzene solution as an antisolvent involves: first, spin-coating the perovskite precursor solution at 800-1000 rpm for 15-20 seconds; then, spin-coating at 4500-5000 rpm for 25-30 seconds, during which a polyoxyethylene chlorobenzene solution is added dropwise.

2. The perovskite solar cell according to claim 1, characterized in that, The concentration of the polyethylene oxide chlorobenzene solution is 0.2~0.4 mg / mL.

3. The perovskite solar cell according to claim 1, characterized in that, The perovskite wet film is MAPbI3.

4. The perovskite solar cell according to claim 1, characterized in that, The hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine].

5. The perovskite solar cell according to claim 1, characterized in that, The electron transport layer is 6,6-phenyl-C 61 -Methyl butyrate.

6. The perovskite solar cell according to claim 1, characterized in that, The buffer layer is 4,7-diphenyl-o-phenanthroline.

7. A method for preparing a perovskite solar cell according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) ITO was selected as the conductive substrate, and a hole transport layer was prepared on the substrate; (2) Spin-coating perovskite precursor solution. During the spin-coating process, chlorobenzene solution of polyethylene oxide is used as an anti-solvent to treat the perovskite wet film, and then annealing is performed to form a perovskite light-absorbing layer passivated by polyethylene oxide. (3) The electron transport layer and the buffer layer are prepared sequentially, and finally the silver electrode is deposited by vapor deposition to obtain a perovskite solar cell with passivated grain boundary defects; In step (2), the spin-coated perovskite precursor solution is first spin-coated at 800-1000 rpm for 15-20 seconds; then spin-coated at 4500-5000 rpm for 25-30 seconds, during which a chlorobenzene solution containing polyethylene oxide is added dropwise.

8. The method for preparing a perovskite solar cell according to claim 7, characterized in that, In step (2), the annealing temperature is 90~100℃ and the time is 10~20 minutes.

9. The method for preparing a perovskite solar cell according to claim 7, characterized in that, In step (1), the preparation of the hole transport layer further includes treating the hole transport layer with N,N-dimethylformamide and toluene.

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