A perovskite solar cell doped with disulfonic acid functionalized ionic liquid and its fabrication method

Abstract

This invention relates to a perovskite solar cell doped with a disulfonic acid-based functionalized ionic liquid and its preparation method. By doping a perovskite precursor solution with a disulfonic acid-based functionalized ionic liquid, this invention effectively controls the crystallization process of perovskite, reduces lead iodide residue, and prepares a perovskite film with better crystallinity, larger and more uniform grain size, and a smoother surface, thereby improving the stability of the perovskite film. Furthermore, the presence of disulfonic acid groups in the ionic liquid anchors uncoordinated Pb ions, inhibits ion migration, and passivates defect states in the perovskite material, significantly improving the quality of the perovskite film and thus enhancing the photoelectric conversion efficiency and long-term stability of the solar cell. Simultaneously, after perovskite film formation, the ionic liquid is mainly distributed at the upper and lower interfaces, achieving synergistic passivation of the two interfaces of the perovskite film, further improving the photoelectric conversion efficiency and long-term stability of the solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology and relates to a perovskite solar cell doped with disulfonic acid functionalized ionic liquid and its preparation method. Background Technology

[0002] Perovskite solar cells have seen rapid development in recent years due to their high photoelectric conversion efficiency and low-cost fabrication. However, because perovskite materials are relatively sensitive to the environment, the prepared polycrystalline perovskite films often contain iodine vacancies, lead vacancies, and residual lead iodide. These vacancy defects and residual lead iodide can cause carrier recombination at grain boundaries and interfaces, thus affecting the efficiency and long-term stability of the device. Passivation of vacancy defects in perovskite films mainly involves adding organic passivating materials containing various functional groups to the perovskite film, improving the morphology of the obtained perovskite film, enhancing crystallinity, and reducing the defect state density.

[0003] Traditional defect passivation materials have limited passivation effects and struggle to achieve synergistic passivation of defects at multiple sites or interfaces. Furthermore, traditional passivation materials suffer from issues related to solubility, toxicity, and thermal stability, posing challenges for large-scale production applications. Additionally, some organic passivation materials often exhibit poor conductivity, which can adversely affect charge transport in solar cell devices.

[0004] Therefore, there is an urgent need for a method to prepare solar cells that can improve the morphology of perovskite thin films, reduce defect state density, and enhance efficiency and long-term stability. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a perovskite solar cell doped with a disulfonic acid-based functionalized ionic liquid and its preparation method. This invention involves adding the disulfonic acid-based functionalized ionic liquid, N-propylsulfonate pyridine p-toluenesulfonate (PSO3HPyOTs), to a perovskite precursor solution, followed by a one-step spin-coating process to obtain a perovskite light-absorbing thin film. The sulfonic acid groups in the ionic liquid can anchor uncoordinated Pb ions in situ through Pb···O coordination, inhibiting ion migration and effectively controlling perovskite crystallization, thereby improving the quality of the perovskite thin film and reducing internal defects in the perovskite material. The PSO3HPyOTs ionic liquid is mainly distributed at the upper and lower interfaces of the perovskite thin film, achieving synergistic passivation of the two interfaces, ultimately resulting in a perovskite solar cell with good performance and stability.

[0006] The objective of this invention can be achieved through the following methods:

[0007] In a first aspect, the present invention provides a method for preparing a perovskite solar cell doped with a disulfonic acid-based functionalized ionic liquid, comprising the following steps: S1. Dissolve perovskite material and disulfonic acid functionalized ionic liquid in a solvent to form a perovskite precursor solution; S2. Spin-coat the surface of the electron transport layer on the conductive substrate with a perovskite precursor solution, and then anneal it to obtain the perovskite active layer. S3. Prepare a hole transport layer on the surface of the perovskite active layer, and then prepare a metal electrode on the surface of the hole transport layer to obtain the final product.

[0008] In one embodiment of the present invention, in step S1, the perovskite material has the general formula ABX3; wherein A is selected from CH3NH3. + CH(NH2)2 + Cs + 、Rb + One or more of them, B is selected from Pb 2+ Sn 2+ One or more of them, X is selected from Cl - ,Br - I - One or more of them.

[0009] Furthermore, the perovskite material is selected from Cs. 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I n Br 1-n )3, MAPbI3, FAPbI3, FA n Cs 1-n One of PbI3; wherein FA is CH(NH2)2 + MA is CH3NH3 + , 0 < n < 1.

[0010] As one embodiment of the present invention, in step S1, the disulfonic acid functionalized ionic liquid includes one or more of the following: N-propylsulfonic acid pyridine p-toluenesulfonate (PSO3HPyOTs), N-butylsulfonic acid pyridine p-toluenesulfonate, 1-butylsulfonic acid-3-methylimidazolium p-toluenesulfonate, 1-propylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1-propylsulfonic acid-3-ethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-methylimidazolium methanesulfonate, 1-butylsulfonic acid-2,3-dimethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-ethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-butylimidazolium trifluoromethanesulfonate, N-propylsulfonic acid pyridine trifluoromethanesulfonate, and N-butylsulfonic acid pyridine trifluoromethanesulfonate.

[0011] As one embodiment of the present invention, in step S1, the concentration of the perovskite material in the perovskite precursor solution is 1.4 M-1.6 M.

[0012] As one embodiment of the present invention, in step S1, the molar amount of the disulfonic acid functionalized ionic liquid is 0.4%-0.7% of the molar amount of perovskite.

[0013] In one embodiment of the present invention, in step S1, the solvent comprises dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 3-5:1.

[0014] In one embodiment of the present invention, in step S2, the conductive substrate is a transparent conductive glass substrate, including one of FTO glass and ITO glass.

[0015] In one embodiment of the present invention, in step S2, the conductive substrate is a substrate that has been cleaned and treated with ultraviolet-ozone; wherein, the cleaning is performed by sequentially cleaning the surface with a cleaning agent, deionized water, acetone, anhydrous ethanol and isopropanol, each cleaning lasting 10-30 minutes; the ultraviolet-ozone treatment lasts for 20-30 minutes.

[0016] In one embodiment of the present invention, in step S2, the electron transport layer includes a SnO2 electron transport layer.

[0017] In one embodiment of the present invention, in step S2, the spin coating speed is 4000-6000 rpm and the time is 20-40 seconds; when the spin coating reaches the 12th-15th second, 100-120 μL of the anti-solvent chlorobenzene is added dropwise.

[0018] In one embodiment of the present invention, in step S2, the annealing temperature is 100-150°C and the time is 20-40 min.

[0019] In one embodiment of the present invention, in step S2, the thickness of the perovskite active layer is 450-550 nm.

[0020] As one embodiment of the present invention, in step S3, the hole transport layer includes one of a tetrakis[N,N-di(4-methoxyphenyl)amino]spiro-OMeTAD hole transport layer and a poly(triarylamine) (PTAA) hole transport layer; the thickness of the hole transport layer is 200-300 nm.

[0021] In one embodiment of the present invention, in step S3, the metal electrode comprises silver with a thickness of 80-110 nm.

[0022] Secondly, the present invention provides a perovskite solar cell doped with a disulfonic acid-based functionalized ionic liquid obtained by the preparation method described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention adds PSO3HPyOTs ionic liquid as an additive to the perovskite precursor solution. On the one hand, it effectively regulates the crystallization process of perovskite, reduces lead iodide residue, and prepares perovskite films with better crystallinity, larger and more uniform grain size, and smoother surface, thereby improving the stability of the perovskite film. On the other hand, the presence of disulfonic acid groups in the PSO3HPyOTs ionic liquid can anchor uncoordinated Pb ions, inhibit ion migration, passivate defect states of perovskite materials, significantly improve the quality of perovskite films, and thus enhance the photoelectric conversion efficiency and long-term stability of solar cells.

[0024] 2. This invention, by doping the perovskite precursor solution with the ionic liquid additive PSO3HpyOTs, significantly enhances its conductivity by approximately 34 times. Simultaneously, after perovskite film formation, the ionic liquid additive, through lattice extrusion and self-settling processes, is primarily dispersed at the upper and lower interfaces of the film, achieving synergistic passivation of the perovskite film's interfaces and forming better interfacial contact. This not only promotes efficient carrier transport but also enhances the film's stability, thereby further improving the photoelectric conversion efficiency and long-term stability of the solar cell. However, adding the ionic liquid additive to the hole transport layer only passivates defects at the lower interface and cannot achieve the aforementioned effects.

[0025] 3. Compared with monosulfonic acid groups, the ionic liquid with disulfonic acid groups used in this invention can provide stronger coordination ability and more nucleation control sites. Therefore, it has significant advantages in improving the crystallinity of thin films, increasing grain size and reducing surface roughness. At the same time, the anchoring ability and passivation effect of disulfonic acid groups are stronger, thereby improving the photoelectric conversion efficiency and long-term stability of solar cells.

[0026] 4. The perovskite solar cell doped with disulfonic acid-based functionalized ionic liquid provided by this invention significantly improves the fill factor, open-circuit voltage, short-circuit current, and photoelectric conversion efficiency of perovskite solar cells. Its photoelectric conversion efficiency can exceed 23.55%, which is 19% higher than that of undoped devices. Furthermore, after being placed at 25°C and 30% relative humidity for 600 hours, the device still retains 80% of its original efficiency.

[0027] 5. The perovskite solar cell fabrication process provided by this invention is simple, efficient and stable, with high reliability and repeatability, and has the prospect of large-area scale-up fabrication and commercial development. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the perovskite solar cell structure in Example 1; Figure 2 The images show the surface morphology of the perovskite films in Examples 1 and Comparative Example 1, where a and d are scanning electron microscope (SEM) images of the comparative and example samples, respectively; b and e are atomic force microscope (AFM) images of the comparative and example samples, respectively; and c and f are Kelvin probe force microscope (KPFM) images of the comparative and example samples, respectively. Figure 3 The images show the time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra of the samples from Example 1 and Comparative Example 1, where a and b are the spectra of the comparative example and the sample from the example, respectively, and c and d are the three-dimensional images of the comparative example and the sample from the example, respectively. Figure 4 The photoelectric conversion efficiency (PCE) and long-term stability of the 25 devices prepared in Example 1 and the devices prepared in Comparative Example 1 are tested; where a is a statistical chart of PCE box type of the samples prepared in Comparative Example 1 and Example 1, and b is the aging test results of the unencapsulated samples of Comparative Example 1 and Example 1 at 25°C and 30% relative humidity. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0030] The disulfonic acid-functionalized ionic liquid used in the embodiments and comparative examples of this invention is: N-propylsulfonic acid pyridine p-toluenesulfonate (PSO3HPyOTs), with CAS number 2260965-27-1, and its structural formula is as follows: .

[0031] Example 1 The perovskite solar cell prepared in this embodiment is a formal structure, such as... Figure 1 As shown, from top to bottom, the structure consists of: FTO conductive substrate / SnO2 electron transport layer / Perovskite perovskite active layer / spiro-OMeTAD hole transport layer / Ag metal electrode. The specific steps are as follows: Step 1: Prepare 1.5 M perovskite Cs0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I n Br 1-n A solution of 3 (where n=0.83) was prepared using a mixed solvent of DMF and DMSO (DMF to DMSO volume ratio of 4:1). The mixture was stirred thoroughly at room temperature for 4 hours, and then N-propylsulfonate pyridine p-toluenesulfonate (PSO3HPyOTs) was added to obtain a perovskite precursor solution. The molar amount of PSO3HPyOTs ionic liquid in the perovskite precursor solution was 0.6% of the molar amount of the perovskite. Step 2: Take FTO conductive glass and clean the surface in sequence with cleaning agent, deionized water, acetone, anhydrous ethanol and isopropanol. Each cleaning takes 20 minutes. After cleaning, blow the substrate dry with a nitrogen gun and treat the dried substrate with ultraviolet-ozone for 25 minutes. Step 3: Dilute the 15% wt SnO2 aqueous dispersion with three times the volume of deionized water, and stir magnetically for 20 minutes to obtain the electron transport layer solution; Step 4: Spin-coat the electron transport layer solution onto the FTO conductive glass surface treated in Step 2 at a spin speed of 2500 rpm for 30 seconds. After spin-coating, heat at 100°C for 60 minutes to obtain the SnO2 electron transport layer. Step 5: Spin-coat 70 μL of the perovskite precursor solution prepared in Step 1 onto the FTO conductive glass surface with the SnO2 electron transport layer obtained in Step 4; prepare the perovskite film using a one-step spin-coating method, with a spin-coating speed of 5000 rpm and a spin-coating time of 30 seconds. When the spin-coating reaches 14 seconds, add 110 μL of the anti-solvent chlorobenzene; after spin-coating, heat and anneal at 100℃ for 40 minutes to obtain a 500 nm thick perovskite film (i.e., the Perovskite active layer).

[0032] Step 6: Dissolve 0.18 g of Spir-OMeTAD and 44 μL of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in acetonitrile (520 mg / mL) and 74 μL of 4-tert-butylpyridine (TBP) in 2 mL of chlorobenzene and stir for 4 hours to obtain the hole transport layer solution. Step 7: Spin-coat the obtained hole transport layer solution onto the surface of the perovskite film obtained in Step 5 at a spin-coating speed of 5000 rpm for 30 s to obtain the Spiro-OMeTAD hole transport layer (200 nm). Step 8: The Spiro-OMeTAD hole transport layer obtained in step 7 is coated with 100 nm of silver as the counter electrode by thermal evaporation.

[0033] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that the doping of PSO3HPyOTs ionic liquid is omitted and a one-step spin coating method is used to prepare perovskite thin films.

[0034] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that the PSO3HPyOTs ionic liquid is replaced with 1-propylsulfonic acid-3-methylimidazolium chloride.

[0035] Performance testing The solar cell samples prepared in Example 1 and Comparative Examples 1-2 were tested for photoelectric conversion efficiency, short-circuit current, open-circuit voltage, and fill factor. The photoelectric conversion efficiency (PCE), short-circuit current (Jsc), open-circuit voltage (Voc), and fill factor (FF) of the solar cells were measured using a Keithley 2400 source meter under simulated AM 1.5G standard sunlight (100 mW / cm²). 2 The light intensity was measured under the following conditions: the solar simulator used was an Enlitech SS-F5-3A, and the light intensity was calibrated using the KG-2 standard silicon cell. All tests were performed in a nitrogen-atmosphere glove box environment. The aperture area of ​​the solar cell was determined by the mask and was 0.0214 cm². 2 The device was subjected to two measurements: reverse scan (1.2 V to -0.1 V, step size 0.02 V) and forward scan (-0.1 V to 1.2 V, step size 0.02 V).

[0036] Table 1 shows the test results of the solar cell samples in the comparative and example cases: Table 1

[0037] As shown in Table 1, compared to Comparative Example 1, Example 1 added PSO3HPyOTs ionic liquid to the perovskite precursor solution, thereby improving the fill factor, short-circuit current, open-circuit voltage, and photoelectric conversion efficiency of the perovskite solar cell. As shown in Comparative Example 2, compared to 1-propylsulfonic acid-3-methylimidazolium chloride, the disulfonic acid groups contained in the PSO3HPyOTs used in Example 1 can better anchor Pb ions, more effectively passivate vacancy defects in the thin film, suppress ion migration, and improve photoelectric conversion efficiency. Figure 4Figure a shows the PCE box-type statistics of the device prepared in Comparative Example 1 and the 25 groups of devices prepared in Example 1. Among the 25 groups of devices, the PCE of the device in Comparative Example 1 ranged from 19.27% ​​to 20.70%, while the PCE of the device in Example 1 increased to 22.34% to 23.55%. The champion device in Example 1 had a PCE of 23.55%, an open-circuit voltage (Voc) of 1.15 V, and a short-circuit current density (Jsc) of 25.05 mA / cm². 2 The fill factor (FF) is 81%.

[0038] Depend on Figure 2 It can be seen that, Figure 2 a shows that the perovskite film in Comparative Example 1 contains obvious pinholes and bright PbI2 clusters, while Figure 2 As shown in Figure 1, the morphology of the perovskite film treated with PSO3HPyOTs was significantly improved, the grain size was more uniform, and the PbI2 clusters disappeared, indicating that there was an effective interaction between the ionic liquid PSO3HPyOTs and the residual PbI2. Figure 2 b shows that the root mean square roughness (RMS) of the sample in Comparative Example 1 is 26.4 nm. Figure 2 The image shows that the roughness of the Example 1 sample after the addition of ionic liquid modification is 22.3 nm. Its smooth and dense perovskite film can achieve better interfacial contact, optimize the carrier transport path, effectively block the permeation of water and oxygen, slow down the degradation rate of the film, and improve the stability of the film. Figure 2 c and f show that the surface potential of the sample in Example 1 is significantly higher than that of the sample in Comparative Example 1, and the distribution is more uniform at the marked lines in the figure. This indicates that the addition of the ionic liquid PSO3HPyOTs effectively modulates the interfacial energy of the perovskite material, further proving that the surface defects of the film are effectively passivated.

[0039] Depend on Figure 3 It can be seen that, Figure 3 a shows the SO3 detected in Comparative Example 1 - and SO3H - The signal mainly originates from the decomposition products of the residual solvent DMSO. Figure 3 b shows that significant SO3 was detected in Example 1. - and SO3H - The signal primarily originates from the added ionic liquid PSO3HPyOTs. From Figure 3 As can be seen from the three-dimensional TOF-SIMS images of c and d, SO3 in the sample of Example 1... - and SO3H -In addition to being distributed in the bulk phase, the ionic liquid is also concentrated on the upper and lower surfaces of the perovskite film. This indicates that the ionic liquid not only plays a role in the bulk phase, but also tends to bind with uncoordinated ions on the perovskite film surface, synergistically passivating the upper and lower surfaces to form better interfacial contact. This not only promotes efficient carrier transport, but also further enhances the stability of the film.

[0040] Stability tests were conducted on the solar cell samples prepared in Example 1 and Comparative Example 1. The stability tests were performed using unencapsulated devices in an air environment at 25°C and 30% relative humidity. The results are as follows: Figure 4 As shown in b, after 600 h, the device of Example 1 still maintains 80% of its original efficiency, while the device of Comparative Example 1 has dropped to only 15% of its initial efficiency after 600 h.

[0041] In summary, the significant improvement in photoelectric conversion efficiency and stability of the device in Example 1 fully demonstrates the feasibility of preparing high-efficiency perovskite solar cells using ionic liquid PSO3HPyOTs modified perovskite thin films.

[0042] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a perovskite solar cell doped with a disulfonic acid-based functionalized ionic liquid, characterized in that, Includes the following steps: S1. Dissolve perovskite material and disulfonic acid functionalized ionic liquid in a solvent to form a perovskite precursor solution; S2. Spin-coat the surface of the electron transport layer on the conductive substrate with a perovskite precursor solution, and then anneal it to obtain the perovskite active layer. S3. Prepare a hole transport layer on the surface of the perovskite active layer, and then prepare a metal electrode on the surface of the hole transport layer to obtain the final product.

2. The preparation method according to claim 1, characterized in that, In step S1, the general formula of the perovskite material is ABX3; Wherein, A is selected from CH3NH3 + CH(NH2)2 + Cs + 、Rb + One or more of them, B is selected from Pb 2+ Sn 2+ One or more of them, X is selected from Cl - ,Br - I - One or more of them.

3. The preparation method according to claim 2, characterized in that, The perovskite material is selected from Cs. 0.05 (FA 0.83 MA 0.17 ) 0.95 Pb(I n Br 1-n )3, MAPbI3, FAPbI3, FA n Cs 1-n One of PbI3; wherein FA is CH(NH2)2 + MA is CH3NH3 + , 0 < n < 1.

4. The preparation method according to claim 1, characterized in that, In step S1, the disulfonic acid functionalized ionic liquid includes one or more of the following: N-propylsulfonic acid pyridine p-toluenesulfonate, N-butylsulfonic acid pyridine p-toluenesulfonate, 1-butylsulfonic acid-3-methylimidazolium p-toluenesulfonate, 1-propylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1-propylsulfonic acid-3-ethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-methylimidazolium methanesulfonate, 1-butylsulfonic acid-2,3-dimethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-ethylimidazolium trifluoromethanesulfonate, 1-butylsulfonic acid-3-butylimidazolium trifluoromethanesulfonate, N-propylsulfonic acid pyridine trifluoromethanesulfonate, and N-butylsulfonic acid pyridine trifluoromethanesulfonate.

5. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the perovskite material in the perovskite precursor solution is 1.4 M-1.6 M; the molar amount of the disulfonic acid functionalized ionic liquid is 0.4%-0.7% of the molar amount of the perovskite.

6. According to the preparation method of claim 1, in step S2, the conductive substrate is a transparent conductive glass substrate, including one of FTO glass and ITO glass; The conductive substrate is a substrate that has undergone cleaning and ultraviolet-ozone treatment; wherein... The cleaning process involves sequentially cleaning the surface with a cleaning agent, deionized water, acetone, anhydrous ethanol, and isopropanol, with each cleaning session lasting 10-30 minutes. The ultraviolet-ozone treatment lasts for 20-30 minutes.

7. The preparation method according to claim 1, characterized in that, In step S2, the electron transport layer includes a SnO2 electron transport layer; The spin coating speed is 4000-6000 rpm, and the time is 20-40 seconds; when the spin reaches 12-15 seconds, 100-120 μL of the anti-solvent chlorobenzene is added dropwise; The annealing temperature is 100-150℃, and the time is 20-40 min; The thickness of the perovskite active layer is 450–550 nm.

8. The preparation method according to claim 1, characterized in that, In step S3, the hole transport layer includes one of tetrakis[N,N-di(4-methoxyphenyl)amino]spirodifluorene hole transport layer and poly(triarylamine) hole transport layer; the thickness of the hole transport layer is 200-300 nm.

9. The preparation method according to claim 1, characterized in that, In step S3, the metal electrode comprises silver and has a thickness of 80-110 nm.

10. A perovskite solar cell doped with a disulfonic acid-functionalized ionic liquid obtained by the preparation method according to any one of claims 1-9.

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