Solution-pre-oxidizable doped organic hole transport layer, method of making and use thereof

Abstract

The application belongs to the technical field of organic semiconductors, and discloses a solution-pre-oxidation doped organic hole transport layer, a preparation method and application thereof. The preparation method comprises the following steps: forming solution A by mixing an organic hole transport material with an organic solvent A; forming solution B by mixing a metal salt with an organic solvent B; dispersing solution B and tert-butylpyridine into solution A to form solution C; blowing an oxidizing gas into solution C to obtain solution D doped with P type; and spin-coating solution D on a light absorber or a substrate to obtain the solution-pre-oxidation doped organic hole transport layer. The preparation method is simple, and the prepared organic hole transport layer has excellent hole mobility and conductivity without long-time oxidation in air. When the organic hole transport layer is used to prepare a perovskite solar cell, the photoelectric conversion efficiency of the perovskite solar cell can reach more than 24%, and the performance and stability of the perovskite solar cell are obviously improved, so the perovskite solar cell has a good application prospect in perovskite solar cell devices.

Description

Technical Field

[0001] This invention relates to the field of organic semiconductor technology, and in particular to a solution-pre-oxidized organic hole transport layer, its preparation method, and its application in perovskite solar cells. Background Technology

[0002] The organic hole transport material used in perovskite solar cells has a very low hole mobility and requires extensive doping with lithium bis(trifluoromethanesulfonylimide) (LiTFSI). It also needs to be placed in air for at least 12 hours. Only by utilizing the combined effect of oxygen and LiTFSI to achieve P-type doping of the organic hole transport layer can a higher hole mobility be obtained.

[0003] However, the hole transport layer doped with LiTFSI exhibits strong hygroscopicity, absorbing moisture from the air and causing degradation of the perovskite layer when exposed to air. Furthermore, the lithium salt added to the hole transport layer, due to the built-in electric field, causes lithium ions to penetrate along the grain boundaries of the perovskite film into the perovskite layer, resulting in severe carrier recombination and thus reducing the performance of perovskite solar cells. The problem of poor stability in perovskite solar cells due to the need for LiTFSI doping in the organic hole transport layer and exposure to air severely hinders the commercialization of perovskite solar cells. Therefore, efficient P-type doping of the organic hole transport layer to improve the stability of perovskite cells has become a critical issue that urgently needs to be addressed. Moreover, the preparation of a lithium salt-free hole transport layer with high mobility is a challenge in obtaining high-performance solar cells with excellent long-term stability.

[0004] Therefore, the present invention provides a solution-pre-oxidized organic hole transport layer, its preparation method and application. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a solution-pre-oxidized organic hole transport layer, its preparation method, and its applications. This invention utilizes free radicals generated by the interaction of metal salts and oxidizing gases to p-type dope organic hole transport materials in solution. The p-type-doped organic hole transport layer exhibits high hole mobility. Furthermore, the organic hole transport layer prepared using this method can be directly used without a subsequent long-term storage period. Perovskite solar cells prepared using this layer exhibit excellent long-term stability and high photoelectric conversion efficiency.

[0006] The solution-pre-oxidized organic hole transport layer of the present invention, its preparation method, and its application are achieved through the following technical solutions:

[0007] The first objective of this invention is to provide a method for preparing a solution-pre-oxidized organic hole transport layer, comprising the following steps:

[0008] Step 1: The organic hole transport material is uniformly dispersed in organic solvent A to form solution A;

[0009] Step 2: The metal salt is uniformly dispersed in organic solvent B to form solution B; and solution B is dispersed with tert-butylpyridine (TBP) into solution A to form solution C;

[0010] Step 3: Inject oxidizing gas into solution C to obtain P-type doped solution D; spin-coat the P-type doped solution D onto a light absorber or substrate to obtain the solution-pre-oxidized organic hole transport layer.

[0011] Furthermore, the organic hole transport material is any one of P3HT (poly-3-hexylthiophene), Spiro-OMeTAD (2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene), PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), and TPD (poly[bis(4-phenyl)(4-butylphenyl)amine]).

[0012] Furthermore, the structural formula of the metal salt is AB2;

[0013] Wherein, A is a metal cation selected from Fe. 2+ Sn 2+ Pb 2+ 、Sm 2+ Eu 2+ Any one of them;

[0014] B is an anion selected from one or more of bis(pentafluoroethanesulfonyl)imide, bis(trifluoromethylsulfonyl)imide, and bis(trifluorosulfonyl)imide.

[0015] Further, the organic solvent A is selected from one or more of chlorobenzene, toluene, xylene, chloroform, dichloromethane, dichloroethane, petroleum ether, diethyl ether, and ethylene diether;

[0016] The organic solvent B is selected from one or more of acetonitrile, DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N-methylpyrrolidone).

[0017] Furthermore, in solution A, the concentration of the organic hole transport material is 5–70 mg / mL;

[0018] In solution B, the molar concentration of the metal salt is 0.1–1 mol / L.

[0019] Furthermore, in solution C, the molar ratio of the metal salt to the organic hole transport material is 0.1 to 1:1;

[0020] The molar ratio of TBP to the metal salt is 1 to 10:1.

[0021] Furthermore, the oxidizing gas is one or more of dry air, oxygen, ozone, and nitrogen dioxide.

[0022] Furthermore, in step 3, the oxidizing gas is introduced for 0.1–30 minutes, and the gas flow rate is appropriately between 0.1 and 1 m³ / min. 3 Between 1 / min, the total volume of gas introduced is 10 to 2000 times the volume of solution C.

[0023] A second objective of this invention is to provide a solution-pre-oxidized organic hole transport layer prepared by the above-described method.

[0024] A third objective of this invention is to provide an application of the aforementioned organic hole transport layer in the fabrication of perovskite solar cells.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention employs a solution pre-oxidation doping technique to directly prepare a high-mobility and stable organic hole transport layer. This eliminates the need for complex processes such as LiTFSI doping and long-term oxidation, allowing for direct application. Compared to organic hole transport layers prepared using traditional doping methods, the entire preparation process is simpler and more readily applicable. Furthermore, the perovskite solar cells with solution-pre-oxidation doped organic hole transport layers prepared using this method exhibit high efficiency and stability, increasing the photoelectric conversion efficiency from a basic 20% to over 24%. This significantly improves the photoelectric conversion efficiency of perovskite solar cells prepared using low-temperature solution methods, demonstrating extremely high application potential. Attached Figure Description

[0027] Figure 1 Optical photographs of the Spiro-OMeTAD solution before and after pre-oxidation prepared in Example 1;

[0028] Figure 2 Infrared spectra of the Spiro-OMeTAD solution before and after pre-oxidation prepared in Example 1;

[0029] Figure 3 The current-voltage curves of the perovskite solar cells of Example 1 and Comparative Example 1 are shown.

[0030] Figure 4 Humidity stability of the perovskite solar cell in Example 1;

[0031] Figure 5 The current-voltage curves of the perovskite solar cells of Example 2 and Comparative Example 2 are shown.

[0032] Figure 6 The current-voltage curves are for the perovskite solar cells of Example 3 and Comparative Example 3. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] This invention provides a solution-pre-oxidized organic hole transport layer, the preparation method of which is as follows:

[0035] Step 1: The organic hole transport material is uniformly dispersed in organic solvent A to form solution A with a concentration of 5-70 mg / mL;

[0036] It should be noted that, considering that the modification principles of common organic hole transport materials in perovskite solar cells are basically the same and that the modifying additives can be used interchangeably, this invention may optionally use any one of P3HT, Spiro-OMeTAD, PTAA and TPD as the organic hole transport material.

[0037] In order to enable the organic solvent A to dissolve and disperse the hole transport material, while ensuring that the organic solvent A does not dissolve the perovskite, the present invention may optionally use one or more of chlorobenzene, toluene, xylene, chloroform, dichloromethane, dichloroethane, petroleum ether, diethyl ether and ethylene diether as organic solvent A to form solution A with the hole transport material.

[0038] Step 2: The metal salt is uniformly dispersed in organic solvent B to form solution B; and solution B is dispersed with tert-butylpyridine (TBP) into the above solution A to form solution C;

[0039] It should be noted that, considering the characteristic of variable-valence metals promoting redox reactions during valence state transitions, this invention selects a metal salt with multiple valence states and an organic solvent B to form solution B. For example, a metal salt with the AB2 structure is selected, where A is a metal cation selected from Fe. 2+ Sn 2+ Pb 2+ 、Sm 2+ Eu 2+ B is any one of the following; B is an anion selected from one or more of bis(pentafluoroethanesulfonyl)imide, bis(trifluoromethylsulfonyl)imide, and bis(trifluorosulfonyl)imide.

[0040] Furthermore, in order to enable organic solvent B to form a homogeneous solution with the metal salt, while also being miscible with organic solvent A to facilitate the formation of solution C for subsequent reactions, the present invention optionally uses one or more of acetonitrile, DMF, DMSO and NMP as organic solvent B to form solution B with the metal salt.

[0041] Step 3: Inject oxidizing gas into the above solution C to obtain P-type doped solution D; spin-coat the above P-type doped solution D onto a light absorber or substrate to obtain the above solution-pre-oxidized organic hole transport layer.

[0042] It should be noted that this invention does not limit the specific type of oxidizing gas, as long as a p-type doped solution D can be obtained. For example, in this invention, one or more of dry air, oxygen, ozone, and nitrogen dioxide can be bubbled into solution C as the oxidizing gas for a time of 0.1 to 30 minutes, and the preferred gas flow rate is 0.1 to 1 m³ / min. 3 / min, so that the total volume of gas blown in is 10 to 2000 times the volume of solution C.

[0043] Example 1

[0044] This embodiment provides a perovskite solar cell with a solution-pre-oxidized organic hole transport layer. The perovskite solar cell of this embodiment adopts a NiP-type device structure, which includes, from bottom to top, a transparent conductive substrate, an electron transport layer, a perovskite photoactive layer, a hole transport layer, and a metal electrode.

[0045] The other parts, except for the hole transport layer, can be prepared using methods and components familiar to those skilled in the art, without any special restrictions, and therefore will not be elaborated here.

[0046] In this embodiment, the hole transport material in the solution-pre-oxidized hole transport layer is Spiro-OMeTAD, and the metal salt used is bis(TFSI)2 (tin trifluoromethanesulfonyl imide). The specific fabrication method of the perovskite solar cell with the solution-pre-oxidized organic hole transport layer in this embodiment is as follows:

[0047] S1. Mix 60 mg of the organic hole transport material Spiro-OMeTAD with 1 mL of chlorobenzene to prepare a Spiro solution, i.e., solution A.

[0048] S2. Mix 200 mg of Sn(TFSI)2 with 1 mL of acetonitrile to prepare solution B;

[0049] S3. Mix solution B with TBP and solution A until homogeneous to form solution C;

[0050] Furthermore, in solution C of this embodiment, the molar ratio of Sn(TFSI)2 to the organic hole transport material Spiro-OMeTAD is 1:1, and the molar ratio of TBP to Sn(TFSI)2 is 5:1.

[0051] S4. Blow oxygen into the mixed solution for 1 minute to obtain a pre-oxidized organic hole transport material solution. After centrifuging the pre-oxidized organic hole transport material solution, take the upper liquid to obtain a P-type doped organic hole transport material solution, i.e., solution D.

[0052] S5. In this embodiment, the perovskite solar cell adopts a device structure of FTO / SnO2 / FAPbI3 / HTL / Au. Solution D is spin-coated onto the perovskite photoactive layer to obtain the hole transport layer described above.

[0053] S6. A layer with an area of ​​0.1 cm² is deposited on the hole transport layer prepared in S5. 2 A 100nm thick Au electrode is used to obtain a perovskite solar cell.

[0054] Furthermore, the perovskite solar cell provided in this embodiment has a photoelectric conversion efficiency of 24.1%.

[0055] Example 2

[0056] This embodiment provides a perovskite solar cell with a solution-pre-oxidized organic hole transport layer. The perovskite solar cell of this embodiment adopts a NiP-type device structure, which includes, from bottom to top, a transparent conductive substrate, an electron transport layer, a perovskite photoactive layer, a hole transport layer, and a metal electrode.

[0057] The other parts, except for the hole transport layer, can be prepared using methods and components familiar to those skilled in the art, without any special restrictions, and therefore will not be elaborated here.

[0058] In this embodiment, the hole transport material in the solution-pre-oxidized hole transport layer is PTAA, and the metal salt used is Sn(TFSI)2; and the specific fabrication method of the perovskite solar cell with the solution-pre-oxidized organic hole transport layer in this embodiment is as follows:

[0059] S1. Mix 10 mg of organic hole transport material PTAA with 1.2 mL of toluene to prepare a PTAA solution, i.e., solution A;

[0060] S2. Mix 200 mg of Eu(TFSI)2 with 1 mL of acetonitrile to prepare solution B;

[0061] S3. Mix solution B with TBP and solution A until homogeneous to form solution C;

[0062] Furthermore, in solution C of this embodiment, the molar ratio of Eu(TFSI)2 to PTAA is 0.1:1, and the molar ratio of TBP to Eu(TFSI)2 is 4:1.

[0063] S4. Blow dry air into the mixed solution for 5 minutes to obtain a pre-oxidized organic hole transport material solution; centrifuge the pre-oxidized organic hole transport material solution and take the upper liquid to obtain a P-type doped organic hole transport material solution, i.e., solution D.

[0064] S5. The perovskite solar cell in this embodiment uses FTO / TiO2 / Cs. 0.05 FA 0.8 MA 0.1 The device structure of PbI3 / HTL / Ag involves spin-coating solution D onto the perovskite photoactive layer to obtain the hole transport layer described above.

[0065] S6. A layer with an area of ​​0.1 cm² is deposited on the hole transport layer prepared in S5. 2 A 100nm thick Ag electrode is used to obtain a perovskite solar cell.

[0066] The perovskite solar cell provided in this embodiment has a photoelectric conversion efficiency of 22.51%.

[0067] Example 3

[0068] This embodiment provides a perovskite solar cell with a solution-pre-oxidized organic hole transport layer. The perovskite solar cell of this embodiment adopts a NiP-type device structure, which includes, from bottom to top, a transparent conductive substrate, an electron transport layer, a perovskite photoactive layer, a hole transport layer, and a metal electrode.

[0069] The other parts, except for the hole transport layer, can be prepared using methods and components familiar to those skilled in the art, without any special restrictions, and therefore will not be elaborated here.

[0070] In this embodiment, the hole transport material in the solution-pre-oxidized hole transport layer is Spiro-OMeTAD, and the metal salt used is europium bis(trifluoromethanesulfonylimide) (Eu(TFSI)2); and the specific fabrication method of the perovskite solar cell with the solution-pre-oxidized organic hole transport layer in this embodiment is as follows:

[0071] S1. Mix 60 mg of the organic hole transport material Spiro-OMeTAD with 1 mL of chlorobenzene to prepare a Spiro solution, i.e., solution A.

[0072] S2. Mix 200 mg of Eu(TFSI)2 with 1 mL of acetonitrile to prepare solution B;

[0073] S3. Mix solution B with TBP and solution A until homogeneous to form solution C;

[0074] Furthermore, in solution C of this embodiment, the molar ratio of Eu(TFSI)2 to the organic hole transport material Spiro is 0.5:1, and the molar ratio of TBP to Eu(TFSI)2 is 5:1.

[0075] S4. Blow oxygen into the mixed solution for 30 seconds to obtain a pre-oxidized organic hole transport material solution; centrifuge the pre-oxidized organic hole transport material solution and take the upper liquid to obtain a P-type doped organic hole transport material solution, i.e., solution D.

[0076] S5. In this embodiment, the perovskite solar cell adopts an ITO / SnO2 / MAPbI3 / HTL / Au device structure. Solution D is spin-coated onto the perovskite photoactive layer to obtain the hole transport layer described above.

[0077] S6. A layer with an area of ​​0.1 cm² is deposited on the hole transport layer prepared in S5. 2 A 100nm thick Au electrode is used to obtain a perovskite solar cell.

[0078] Furthermore, the photoelectric conversion efficiency of the perovskite solar cell provided in this embodiment is 22.84%.

[0079] Example 4

[0080] This embodiment provides a perovskite solar cell with a solution-pre-oxidized organic hole transport layer, and the only difference between this comparative example and Example 1 is:

[0081] In this embodiment, the organic hole transport material is TPD, the organic solvent A is dichloromethane, and the concentration of the organic hole transport material in solution A is 5 mg / mL.

[0082] The metal salt is bis(pentafluoroethanesulfonyl)imine iron, and the organic solvent B is DMF; the molar concentration of the metal salt in solution B is 0.1 mol / L.

[0083] In solution C, the molar ratio of the metal salt to the organic hole transport material is 0.1:1; the molar ratio of TBP to the aforementioned metal salt is 1:1.

[0084] Dry air is used as the oxidizing gas, and the blowing time is 0.1 min. The preferred gas flow rate is 0.1 cm³. 3 / min.

[0085] Example 5

[0086] This embodiment provides a perovskite solar cell with a solution-pre-oxidized organic hole transport layer, and the only difference between this comparative example and Example 1 is:

[0087] In this embodiment, the organic hole transport material is P3HT, the organic solvent A is toluene, and the concentration of the organic hole transport material in solution A is 70 mg / mL.

[0088] The metal salt is Sm(TFSI)2, and the organic solvent B is NMP; the molar concentration of the metal salt in solution B is 1 mol / L.

[0089] In solution C, the molar ratio of metal salt to organic hole transport material is 1:1; the molar ratio of TBP to metal salt is 10:1.

[0090] Nitrogen dioxide is used as the oxidizing gas, and its blowing time is 30 minutes. The preferred gas flow rate is 1 cm³. 3 / min.

[0091] Comparative Example 1

[0092] This comparative example provides a perovskite solar cell, and the only difference between this comparative example and Example 1 is that:

[0093] In this comparative example, the hole transport layer is a hole transport layer using the conventional doping method (LiTFSI doping).

[0094] Comparative Example 2

[0095] This comparative example provides a perovskite solar cell, and the only difference between this comparative example and Example 2 is that:

[0096] In this comparative example, the hole transport layer is a hole transport layer using the conventional doping method (LiTFSI doping).

[0097] Comparative Example 3

[0098] This comparative example provides a perovskite solar cell, and the only difference between this comparative example and Example 3 is that:

[0099] In this comparative example, the hole transport layer is a hole transport layer using the conventional doping method (LiTFSI doping).

[0100] Experimental Section

[0101] (I) Infrared spectrum

[0102] Taking Example 1 as an example, this invention observes the solution state before and after oxygen introduction, such as... Figure 1 As shown, Figure 1The image on the left shows a chlorobenzene solution containing Spiro-OMeTAD, a hole transport material, before oxygen was introduced. Figure 1 The image on the right shows the hole transport material solution after oxygen was introduced. The color of the solution changed, indicating that Spiro-OMeTAD in chlorobenzene underwent an oxidation reaction under the combined action of Sn(TFSI)2 and oxygen.

[0103] Furthermore, this invention performs infrared spectroscopy tests on the solution before and after oxygen introduction, and the test results are as follows: Figure 2 As shown, by Figure 2 It can be seen that after oxygen is introduced, the Spiro-OMeTAD molecules in the solution are oxidized and bonded to the Sn(TFSI)2 anion, achieving p-type doping of Spiro-OMeTAD and improving its hole mobility. This indicates that the steps in Example 1 achieve solution oxidation doping treatment of the hole transport material Spiro-OMeTAD. Spin-coating this solution yields a hole transport layer with high hole mobility, which does not require further oxidation in air.

[0104] (II) Performance Parameter Testing of Perovskite Solar Cells

[0105] To illustrate the perovskite solar cell with a solution-pre-oxidized organic hole transport layer provided by the present invention, the perovskite solar cells with a solution-pre-oxidized organic hole transport layer prepared in Examples 1-3 were used as the experimental group, and the perovskite solar cells with a hole transport layer prepared in Comparative Examples 1-3 using the conventional doping method (LiTFSI doping) were used as the control group. The performance parameters of the two cells were tested, and the test results are shown in Table 1.

[0106] Table 1. Test results of performance parameters of perovskite solar cells

[0107] Open circuit voltage / V <![CDATA[Short-circuit current density / (mA / cm 2 )]]> Fill factor / % Conversion efficiency / % Comparative Example 1 1.148 22.723 70.875 18.485 Example 1 1.170 22.758 74.047 19.715 Comparative Example 2 1.06 24.88 76.74 20.24 Example 2 1.11 24.85 77.98 21.51 Comparative Example 3 1.10 25.02 76.32 21.00 Example 3 1.13 25.08 80.62 22.84

[0108] (II) Current-voltage curves of perovskite solar cells

[0109] This invention uses the perovskite solar cells provided in Examples 1-3 as the experimental group and the perovskite solar cells of Comparative Examples 1-3 as the control group. The performance parameters of each were tested, and the test results are as follows: Figures 3 to 6 As shown. Among them, Figure 3 The current-voltage curves of the perovskite solar cells of Example 1 and Comparative Example 1 are shown. Figure 4 Humidity stability of the perovskite solar cell with a solution-pre-oxidized organic hole transport layer provided in Example 1; Figure 5 The current-voltage curves of the perovskite solar cells of Example 2 and Comparative Example 2 are shown. Figure 6 The current-voltage curves are for the perovskite solar cells of Example 3 and Comparative Example 3.

[0110] And the above Table 1 and Figures 3-6 It is known that the open-circuit voltage, short-circuit current, and fill factor of the perovskite solar cell with a solution-pre-oxidized organic hole transport layer of the present invention are significantly improved compared with the original perovskite solar cell. This is because the solution-pre-oxidized organic hole transport layer has a high hole mobility, which promotes the extraction of holes in the perovskite film and facilitates the transport and collection of holes generated in the perovskite film into the hole transport layer. As a result, the photoelectric conversion efficiency of the perovskite solar cell with a solution-pre-oxidized organic hole transport layer is increased from 20% of the original perovskite solar cell to more than 24%.

[0111] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a solution-pre-oxidized organic hole transport layer, characterized in that, Includes the following steps: Step 1: The organic hole transport material is uniformly dispersed in organic solvent A to form solution A; Step 2: The metal salt is uniformly dispersed in organic solvent B to form solution B; and solution B and tert-butylpyridine are dispersed in solution A to form solution C; Step 3: Inject oxidizing gas into solution C to obtain P-type doped solution D; spin-coat the P-type doped solution D onto a light absorber or substrate to obtain the solution-pre-oxidized organic hole transport layer. The structural formula of the metal salt is AB2; Wherein, A is a metal cation selected from Fe. 2+ Sn 2+ Pb 2+ 、Sm 2+ Eu 2+ Any one of them; B is an anion selected from one or more of bispentafluoroethanesulfonylimide and bistrifluoromethylsulfonylimide.

2. The preparation method according to claim 1, characterized in that, The organic hole transport material is any one of poly(3-hexylthiophene), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and poly[bis(4-phenyl)(4-butylphenyl)amine].

3. The preparation method according to claim 1, characterized in that, The organic solvent A is selected from one or more of chlorobenzene, toluene, xylene, chloroform, dichloromethane, dichloroethane, petroleum ether, diethyl ether, and ethylene diether; The organic solvent B is selected from one or more of acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

4. The preparation method according to claim 1, characterized in that, In solution A, the concentration of the organic hole transport material is 5~70 mg / mL; In solution B, the molar concentration of the metal salt is 0.1~1 mol / L.

5. The preparation method according to claim 1, characterized in that, In solution C, the molar ratio of the metal salt to the organic hole transport material is 0.1 to 1:1; The molar ratio of tert-butylpyridine to the metal salt is 1 to 10:

1.

6. The preparation method according to claim 1, characterized in that, The oxidizing gas is one or more of dry air, oxygen, ozone, and nitrogen dioxide.

7. The preparation method according to claim 1, characterized in that, In step 3, the oxidizing gas is introduced for 0.1 to 30 minutes.

8. An organic hole transport layer that can be solution-pre-oxidized and doped by the preparation method according to any one of claims 1-7.

9. The use of the organic hole transport layer of claim 8 in the fabrication of perovskite solar cells.

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