Method for improving photoelectric conversion efficiency and stability of perovskite solar device

Abstract

The application belongs to the method for improving the photoelectric conversion efficiency and stability of a device, and particularly relates to a method for reducing the defect density and surface potential of an organic-inorganic hybrid perovskite film by using a N-heterocyclic ring passivation agent through π-Pb 2+ The application relates to a method for reducing defect density and surface potential of an organic-inorganic hybrid perovskite film and enabling band bending of a perovskite material and improving charge extraction efficiency. An additive is added in a reverse solvent during preparation of an organic-inorganic hybrid perovskite film, and is attached and gathered on the surface of the formed organic-inorganic hybrid perovskite film. The application effectively passivates defects of the perovskite film by introducing a N-heterocyclic ring organic small molecule into the perovskite film, and improves the stability of the film and a corresponding device. The material used is low in cost and easy to realize in a process.

Description

Technical Field

[0001] This invention relates to a method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices, specifically involving the use of an N-heterocyclic passivating agent via π-Pb 2+ A method to reduce the defect concentration and surface potential of organic-inorganic hybrid perovskite films through interactions, and to bend the band structure of perovskite materials and improve charge extraction efficiency. Background Technology

[0002] Metal halide perovskite materials possess high absorption coefficients, tunable band gaps, and long carrier diffusion lengths. These materials exhibit the photoelectric effect, converting light energy into electrical energy. Solar cells made from these materials hold promise as reliable energy supply devices. In recent years, extensive research has focused on perovskite solar cells, increasing photoelectric conversion efficiency from 3.8% in 2009 to 25.5% in 2020, thus making them a strong competitor in the photovoltaic field. According to the Schockley-Queisser limit, the theoretical maximum photoelectric efficiency for a single-junction perovskite solar cell is approximately 30%, indicating that there is still room for efficiency improvement. However, perovskite materials have many inherent defects, and band or energy level mismatches often exist at the interfaces between different materials in the device. This leads to significant charge recombination and inefficient charge trapping within the cell, limiting the development of perovskite solar cells.

[0003] Various strategies have been developed to mitigate the aforementioned adverse factors. Chemical doping is considered an effective method, capable of tuning Fermi level positions and enhancing charge transport capabilities, thereby enabling the fabrication of a series of high-efficiency devices. For example, PCBM is commonly used as an electron transport layer, but Wu et al. introduced it into FA via an antisolvent. 0.85 MA 0.15 Pb(I 0.85 Br 0.15 3) This formed a graded heterojunction, which improved photoelectron collection while reducing charge recombination loss. Additionally, the CuI-thiourea complex was used to passivate MAPbI x Cl 3-x Trapped states in perovskites and extended dissipation regions in inherent heterojunctions enhance hole transport performance and reduce charge recombination in devices. Recently, Huang's group doped F4TCNQ into MAPbI3, altering the work function of the perovskite material, which similarly improved hole transport performance and thus device performance. Building upon these previous reports, we have developed and synthesized a novel organic small molecule. This additive lowers the surface potential of the perovskite film, increases the work function, induces band bending, promotes hole extraction, and reduces charge recombination at the interface. Summary of the Invention

[0004] The purpose of this invention is to improve the photoelectric conversion efficiency and stability of perovskite solar cells.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] After spin-coating the organic-inorganic hybrid perovskite precursor for a period of time, chlorobenzene containing additives is sprayed onto the film, and then the additives adhere and aggregate on its surface.

[0007] The additive used is an imidazo-indolizine derivative, scientifically named 1-(4-bromophenyl)-6,7-diphenylimidazo[5,1,2-cd]indolizine, abbreviated as PDPII.

[0008] Preferred:

[0009] Mix the required components in the specified proportions, add the DMSO / DMF mixed solvent, and stir thoroughly until completely dissolved to form FA. 0.85 MA 0.15 Pb(I 0.85 Br 0.15 ) 3-x Cl x Precursor solution. Perovskite films were then prepared by spin coating. The control group used a chlorobenzene antisolvent without additives, while the experimental group contained different concentrations of additives. The resulting intermediate films were then heat-treated.

[0010] The molar concentration of the additive in the antisolvent chlorobenzene is 0.2 to 5 mmol / L.

[0011] The heat treatment temperature of the film is 100℃.

[0012] The next best option is:

[0013] An additive was added to the antisolvent chlorobenzene, a thin film was prepared by spin coating, and then heated to 100°C before assembling the battery device. Within the additive concentration range of 1 mmol / L, the stability of the battery device was gradually improved; however, further changes in concentration resulted in a decrease in stability.

[0014] The additive is an imidazoindolizine derivative, scientifically named 1-(4-bromophenyl)-6,7-diphenylimidazo[5,1,2-cd]indolizine, abbreviated as PDPII.

[0015] The organic-inorganic hybrid perovskite film has the organic-inorganic hybrid perovskite structure ABX3, where A is a cation containing methylamine CH3NH3 (MA) ions, formamidinium NH2-CH=NH2 (FA) ions, and cesium (Cs) ions; B is a Pb ion, and X is I, Br, or Cl ions.

[0016] The above methods reduce the surface potential and increase the work function of the perovskite thin film, and the resulting band bending promotes hole extraction and reduces charge recombination at the interface, which greatly improves the operating life of the device. This is particularly important for the commercial application of perovskite solar cell devices.

[0017] Advantages of this invention:

[0018] This invention introduces PDPII small molecules into perovskite thin films, which can effectively reduce the surface potential of the perovskite film, increase the work function, induce band bending, promote hole extraction, reduce charge recombination at the interface, and improve the stability of the film and corresponding devices. The materials used are low-cost and easy to implement in the process.

[0019] This invention introduces PDPII small molecules into the initial thin film, which can be prepared using conventional spin-coating methods. The imidazoindole ring system contained in the material has a strong interaction with the Pb ions of the perovskite.

[0020] The perovskite thin films containing PDPII small molecules prepared according to the method of the present invention have fewer defects and reduced exciton recombination. The perovskite thin films prepared based on the present invention exhibit higher fluorescence intensity and longer fluorescence lifetime, and the photostability of the corresponding devices is also significantly improved.

[0021] The process of this invention is easy to operate, has good repeatability, and is suitable for large-scale production. Attached Figure Description

[0022] Figure 1 The XRD patterns of perovskite thin films prepared before and after the introduction of PDPII into the antisolvent are provided in the embodiments of the present invention.

[0023] Figure 2 SEM images of perovskite films prepared before and after the introduction of PDPII into the antisolvent provided in this embodiment of the invention; the left image is before the addition of PDPII, and the right image is after the addition of 1 mmol / L PDPII.

[0024] Figure 3 The PL spectra of perovskite thin films prepared before and after the introduction of PDPII into the antisolvent are provided in the embodiments of the present invention.

[0025] Figure 4 IV curves of perovskite solar cells prepared before and after the introduction of PDPII into the antisolvent, as provided in the embodiments of the present invention.

[0026] Figure 5 Stability curves of unencapsulated perovskite solar cells prepared before and after the introduction of PDPII into the antisolvent, as provided in the embodiments of the present invention.

[0027] Figure 6 This is the synthetic route for PDPII.

[0028] Figure 7 It is an electrochemical synthesis reaction apparatus.

[0029] Figure 8 For PDPII 1 H NMR spectrum.

[0030] Figure 9 For PDPII 13 C10 NMR spectrum.

[0031] Figure 10 The image shows the HRMS spectrum of PDPII. Detailed Implementation

[0032] 1. Device fabrication

[0033] First, the etched FTO glass substrate was sequentially washed with cleaning agent, deionized water, ethanol, and isopropanol, and then dried with a nitrogen gun. The substrate was then treated with O2-plasma for 10 min. A dense TiO2 layer was first deposited on the substrate using atomic layer deposition (ALD), followed by calcination at 500°C for 30 min in air. A SnO2 precursor solution (SnCl4 aqueous solution) was then spin-coated onto the dense film at 3000 rpm for 30 s, followed by further heating at 180°C for 30 min to obtain a dense TiO2 / SnO2 electron transport layer.

[0034] Secondly, accurately weigh 6.4 mg MAI, 13.5 mg FABr, 24.6 mg CsI, 39.6 mg PbBr2, 190.4 mg FAI, and 591.2 mg PbI2, and dissolve them in 1 mL of a mixed solvent, DMSO:DMF = 4:1, v / v. In addition, the precursor also contains 0.35 equivalents of MACl. 0.9 Cs 0.07 MA 0.03 Pb(I 0.92 Br 0.08The 3% excess PbI₂ precursor solution was spin-coated at 1000 rpm for 10 s, followed by 4000 rpm for 30 s. 200 μL of chlorobenzene was sprayed 10 s before the end of the second step. The control group chlorobenzene did not contain PDPII, while the experimental group contained PDPII at an optimal concentration of 1 mmol / L. The resulting intermediate film was annealed at 100 °C for 40 min. Compared to the experimental group, the control group perovskite film showed reduced XRD peak intensity due to PDPII surface coverage. No significant shift in peak position and the absence of new peaks indicated that the doping process did not induce new phase formation (see [link to relevant documentation]). Figure 1 Meanwhile, SEM images show that the addition of PDPII leads to a reduction in free PbI2, and PDPII itself also accumulates on the surface and at grain boundaries of perovskite grains (see...). Figure 2 Fluorescence characterization also showed that PDPII passivation exhibited fewer carrier recombination centers, improving the film quality (see [link]). Figure 3 ).

[0035] Finally, following existing technology, a hole transport layer (spiro-OMeTAD) and a gold electrode were spin-coated onto the surfaces of the two different perovskite thin films obtained above, respectively, and assembled into solar cell devices. IV performance was then measured under forward and reverse sweep conditions between 0V and 1.2V. The device containing PDPII showed a significant improvement in efficiency and a substantial reduction in hysteresis (see [link to relevant documentation]). Figure 4 This indicates a reduction in recombination within the device.

[0036] The solar cell obtained in this embodiment was placed in an environment with 20% humidity to test its air stability. Figure 5 It is evident that the stability of the battery is improved to some extent by doping.

[0037] 2. Synthesis of PDPII

[0038] See the additive synthesis route. Figure 6 The apparatus for the second step of the reaction is shown below. Figure 7 .

[0039] To a thoroughly dried 100 mL round-bottom flask, add 13 mmol of 2-aminopyridine, 10 mmol of α-bromoacetophenone, 15 mmol of NaHCO3, and 20 mL of ethanol. Stir the mixture at 80 °C for 3–4 h. After confirming the reaction is complete by TLC, cool the mixture to room temperature and add 15 mL of water to the flask. Extract three times with dichloromethane, combine the organic phases, and dry with anhydrous MgCl2. The crude product was concentrated by rotary evaporation and purified by column chromatography (petroleum ether:ethyl acetate = 3:1 v / v), yielding an intermediate in 90% yield.

[0040] Add 0.1 mmol of the purified intermediate, 0.15 mmol of 1,2-diphenylacetylene, 0.2 mmol of CH₂ClCOONa, 0.2 mmol of KPF₆, and 0.001 mmol of Cp*Rh(MeCN)₃(SbF₆)₂ to a 10 mL puff-shaped flask. Dissolve the reagents in 3.75 mL of hexafluoroisopropanol and 1.245 mL of water. Fit the reaction flask with a rubber stopper fitted with a graphite felt anode (1 cm × 1 cm × 0.5 cm) and a platinum cathode (1 cm × 1 cm × 0.1 mm). Stir the reaction mixture at a constant current of 4 mA and 70 °C for 2 h. After the reaction is complete, purify the crude product by column chromatography using dichloromethane:methanol = 49 / 1 v / v eluent to obtain a bright yellow solid in 40% yield.

[0041] PDPII NMR and high-resolution mass spectrometry data. See the relevant NMR spectra below. Figures 8-9 . 1 H NMR (500MHz, Chloroform-d, δ, ppm): 8.06 (dd, J=5.6, 3.0Hz, 1H), 8.02–7.96 (m, 2H), 7.71–7.66 (m, 2H), 7.49–7.30 (m, 10H). 13 C NMR (126MHz, CDCl3, ppm): δ148.92,139.38,133.37,133.19,132.02,131.30,131.05,130.54,130.50,130.39,129.63,129.08,128.65,1 28.17,128.03,127.86,127.67,127.22,126.79,126.65,126.53,123.78,123.34,112.56,112.20,111.08,110.48.HRMS(ESI-TOF,[M+H] + ):For C 27 H 18 BrN2,449.0653; found:449.0653.

Claims

1. A method utilizing π-Pb 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... An additive is added to the antisolvent during the preparation of organic-inorganic hybrid perovskite thin films. The additive adheres to and aggregates on the surface of the formed organic-inorganic hybrid perovskite thin film. The additive is scientifically named 1-(4-bromophenyl)-6,7-diphenylimidazo[5,1,2-cd]indolizine, abbreviated as PDPII.

2. The method of utilizing π-Pb according to claim 1 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... This reduces the defect concentration and surface potential of organic-inorganic hybrid perovskite films, and enables band bending in perovskite materials, thereby improving charge extraction efficiency.

3. The method of utilizing π-Pb according to claim 1 or 2 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... The molar concentration of PDPII in the antisolvent chlorobenzene is 1 mmol / L.

4. The method of utilizing π-Pb according to claim 1 or 2 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... After spin-coating an organic-inorganic hybrid perovskite precursor for a period of time, chlorobenzene containing additives is sprayed onto the film, and then the additives adhere and aggregate on its surface; wherein, the solvent of the precursor solution is a mixture of N,N-dimethylformamide and dimethyl sulfoxide.

5. The method of utilizing π-Pb according to claim 2 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... The heat treatment temperature of the thin film is 100°C. o C.

6. The use of π-Pb according to claim 1 or 2 2+ A method for improving the photoelectric conversion efficiency and stability of perovskite solar cell devices through interaction, characterized in that... The organic-inorganic hybrid perovskite thin film has the organic-inorganic hybrid perovskite structure ABX3, where A is an alloy containing methylamine ions, formamidinium ions and cesium ions as cations; B is one or two of Pb metal ions and Sn metal ions; and X is one or more of I, Br, and Cl ions.

7. An organic-inorganic hybrid perovskite thin film prepared by the method described in claim 1, characterized in that, Organic-inorganic hybrid perovskite films doped with PDPII were prepared according to the method described in claim 1.

8. An application of the thin film according to claim 7, characterized in that, The organic-inorganic hybrid perovskite thin film doped with PDPII is used in solar cells to improve photoelectric conversion efficiency and stability.

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