Method for preparing cesium lead iodide all-inorganic perovskite solar cell by doping nematic liquid crystal small molecules into P3HT hole transport layer

Abstract

The present invention relates to a method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a hole transport layer, belonging to the field of solar cell research. The cesium lead iodide perovskite solar cell described in the present invention has a normal structure, which includes a conductive glass, an electron transport layer, a perovskite active layer, a hole transport layer and a metal electrode from bottom to top. The present invention mainly dopes a nematic liquid crystal small molecule into the precursor solution of the P3HT hole transport material, and then spin-coats it on the surface of the cesium lead iodide perovskite active layer, and then assembles a cesium lead iodide all-inorganic perovskite solar cell. By this method, the hole mobility is improved, the energy level matching degree at the interface between the perovskite and P3HT is improved, and the surface defects of the perovskite are passivated, so as to improve the hole extraction and transport ability and reduce the non-radiative recombination loss of carriers; at the same time, the hydrophobic functional groups on the nematic liquid crystal molecules significantly improve the stability of the cesium lead iodide perovskite solar cell in air.

Description

Technical Field

[0001] The present invention belongs to the research field of perovskite solar cells, and specifically relates to a method for preparing a high-performance cesium-lead-iodine all-inorganic perovskite solar cell by utilizing a nematic liquid crystal small molecule-doped P3HT hole transport layer. Background Art

[0002] In 2009, Japanese scientist Tsutomu Miyasaka first introduced the perovskite structure CH3NH3PbX3 into dye-sensitized solar cells, and since then people have begun to study perovskite solar cells. In the following decade, researchers have continuously improved the preparation process, device structure, and device performance of perovskite cells, which has led to a continuous increase in the photoelectric conversion efficiency of perovskite cells. So far, the highest perovskite cell device efficiency has reached 25.7%, which is comparable to silicon-based solar cells. However, traditional high-efficiency perovskite solar cells use an organic-inorganic hybrid perovskite system, in which the organic cation (MA) + , FA + The poor thermal stability of perovskite solar cells (PSCs) has severely hampered the commercialization of PSCs. However, all-inorganic PSCs, which utilize cesium ions instead of organic cations, have attracted widespread attention in recent years due to their excellent thermal stability. Cesium lead iodide perovskite (CsPbI3) has the narrowest band gap (~1.73 eV) and theoretically offers the potential for the highest-efficiency PSCs.

[0003] It should be pointed out that CsPbI3 perovskite has poor humidity stability. Under high humidity conditions, its black perovskite phase will quickly transform into a yellow non-perovskite phase, which makes the preparation conditions of CsPbI3 perovskite solar cells relatively harsh. However, most of the high-efficiency CsPbI3 perovskite solar cells reported so far use Spiro-OMeTAD as the hole transport layer. During the preparation of the Spiro-OMeTAD hole transport layer, hygroscopic lithium salt (Li-TFSI) and corrosive tetra-tert-butylpyridine (tBP) need to be added. It also needs to be oxidized for a long time in an air environment to improve its hole mobility. However, these processes are very unfavorable to the stability of CsPbI3 perovskite solar cells. Poly (3-hexylthiophene) (P3HT) has excellent optoelectronic properties and hydrophobicity, and does not require doping. It can directly replace Spiro-OMeTAD as the hole transport layer of CsPbI3 perovskite solar cells.

[0004] However, for the time being, there is little research on CsPbI3 perovskite solar cells based on the P3HT hole transport layer, and the efficiency is also relatively low. This is mainly because the hole mobility of P3HT itself is lower than that of Spiro-OMeTAD, and the energy level difference between P3HT and CsPbI3 perovskite is relatively large, which limits the extraction and transport of holes. In addition, due to the wet preparation process and the inherent soft lattice characteristics of perovskite materials, a large number of surface and interface defects will inevitably be generated during the crystallization and film formation process, resulting in serious carrier non-radiative recombination losses. Therefore, developing an effective solution that can simultaneously solve the problems of low hole mobility of P3HT, energy level matching at the interface between P3HT and CsPbI3 perovskite, large surface and interface defect density of CsPbI3, and poor humidity stability is of great significance for the development of low-cost and high-efficiency all-inorganic CsPbI3 perovskite solar cells. Summary of the Invention

[0005] The technical problem to be solved by the present invention is as follows: Aiming at the problems of low hole mobility of P3HT, energy level matching at the interface between P3HT and CsPbI3 perovskite, large surface and interface defect density of CsPbI3, and poor humidity stability, a new method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule 4-cyano-4-pentylbiphenyl (5CB) into the P3HT hole transport layer is invented. This method mainly involves doping a nematic liquid crystal small molecule 4-cyano-4-pentylbiphenyl (5CB) into the precursor solution of the P3HT hole transport material, and then spin-coating it on the surface of the CsPbI3 perovskite active layer to form a P3HT:5CB doped film as the hole transport layer, and then assembling it into a CsPbI3 all-inorganic perovskite solar cell. By using P3HT doped with 5CB as the hole transport layer, the performance of CsPbI3 all-inorganic perovskite solar cells can be improved from the following four aspects: 1) improving the carrier mobility of the hole transport layer and enhancing the hole transport ability; 2) optimizing the energy level matching degree between the perovskite and the P3HT hole transport layer and increasing the extraction efficiency of holes at the perovskite / hole transport layer interface; 3) passivating the surface defects of the perovskite and reducing the non-radiative recombination loss of carriers at the perovskite / hole transport layer interface; 4) the strong coordination effect between the cyano group in 5CB and the lead ions in the perovskite and the hydrophobic functional group pentyl in 5CB significantly improve the stability of CsPbI3 perovskite solar cells in air.

[0006] Technical solutions adopted to solve its technical problems: (Describe the deficiencies or problems in the prior art and the technical means used to solve the technical problems in the prior art. The technical solutions of this patent application should be specifically, clearly and completely described in combination with the drawings, including both the technical content of the improved part and the technical content of the part that has not been improved (or retained) in the prior art. For example: the structure of the product, the connection relationship, the transmission relationship, the working principle and the working process; for inventions in the chemical and pharmaceutical fields, the process steps and the reaction conditions for each step (such as temperature, time, pressure, flow rate, etc.) should be given; or the components and content ranges of the formula. When the claimed scope is relatively large, at least three or more implementation schemes should be given.)

[0007] See the appendix for specific preparations)

[0008] The technical solutions of the present invention are as follows:

[0009] A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a hole transport layer of poly(3-hexylthiophene) (P3HT) with a nematic liquid crystal small molecule 4-cyano-4'-pentylbiphenyl, comprising the following steps:

[0010] Step 1: Prepare a n-butanol solution of diisopropyl bis(acetylacetonate) titanate with a concentration of 0.15 - 0.2 mol / L; prepare a cesium lead iodide all-inorganic perovskite precursor solution with a concentration of 0.6 - 0.8 mol / L; prepare a chlorobenzene solution of P3HT with a concentration of 10 - 15 mg / ml, and then add a nematic liquid crystal small molecule thereto to prepare a required hole transport layer precursor solution.

[0011] Step 2: Spin-coat the prepared n-butanol solution of diisopropyl bis(acetylacetonate) titanate on a cleaned FTO conductive glass, and then calcine it to prepare a titanium dioxide electron transport layer film, where the FTO conductive glass serves as the anode of the battery;

[0012] Step 3: Spin-coat the prepared cesium lead iodide all-inorganic perovskite precursor solution on the titanium dioxide electron transport layer prepared in Step 2, and heat-treat it to form a perovskite active layer film;

[0013] Step 4: Spin-coat the prepared hole transport layer precursor solution on the surface of the perovskite active layer film prepared in Step 3, and heat-treat it to form a hole transport layer film;

[0014] Step 5: Evaporate a metal electrode on the surface of the hole transport layer film obtained in Step 4 to complete the assembly of the cesium lead iodide all-inorganic perovskite solar cell.

[0015] As a preferred method: the method for preparing the CsPbI3 all-inorganic perovskite precursor solution is to dissolve cesium iodide (CsI) and hydrogen lead iodide (HPbI3) in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar mass ratio of 1:1. The volume ratio of the DMF and DMSO solvents is 4:1 to form a CsPbI3 perovskite precursor solution.

[0016] As a preferred method: the nematic liquid crystal small molecule described in step one is 4-cyano-4-pentylbiphenyl (5CB), and its concentration in the chlorobenzene solution of P3HT is 10-20 mM.

[0017] As a preferred method: the spin coating method described in step two is static spin coating, the rotation speed is 2500-4000 revolutions / min, and the spin coating time is 30 s; after spin coating, it is first annealed at 125-135 °C for 2-5 min; then transferred to a muffle furnace and annealed at 450 °C at a heating rate of 2 °C / min for 60 min;

[0018] As a preferred method: the spin coating method of the perovskite precursor solution described in step three is dynamic spin coating, the rotation speed is 2000-3000 revolutions / min, and the spin coating time is 30 s; after spin coating, it is first pre-annealed at 70 °C for 2-5 min, and then annealed at 180-210 °C for 5-20 min;

[0019] As a preferred method: the spin coating method described in step four is static spin coating, the rotation speed is 3000 revolutions / min, and the spin coating time is 60 s; after spin coating, it is annealed at 120 °C for 2-5 min;

[0020] As a preferred method: the thickness of the metal electrode described in step five is 80-100 nm; the metal type is any one of gold (Au), silver (Ag), and copper (Cu);

[0021] Advantages of the present invention: The present invention uses 5CB-doped P3HT as the hole transport layer of the CsPbI3 all-inorganic perovskite solar cell, which can improve the hole mobility of P3HT, optimize the energy level matching degree between the perovskite and P3HT, and passivate the surface defects of the perovskite, thereby effectively promoting the extraction and transport of holes at the interface between the perovskite and P3HT, reducing the non-radiative recombination loss of carriers at the interface, and thus significantly improving the open circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency (PCE). In addition, due to the hydrophobic functional group pentyl chain and the strongly coordinating cyano functional group in the 5CB molecule, the humidity stability of the CsPbI3 all-inorganic perovskite solar cell in air has also been greatly improved. This method has a simple process and is suitable for the preparation of flexible or large-area devices. Description of the Drawings

[0022] Figure 1 It is the structure of a CsPbI3 perovskite solar cell. FTO is the anode, TiO2 is the electron transport layer, CsPbI3 is the perovskite active layer, P3HT:5CB is 5CB-doped P3HT as the hole transport layer, and Ag is the cathode.

[0023] Figure 2 It is the optimal current-voltage curve of CsPbI3 solar cells with different P3HT as the hole transport layer. "control" is a CsPbI3 solar cell based on pure P3HT. The open-circuit voltage of this cell is 1.07V, and the short-circuit current density is 20.55mA / cm 2 , the fill factor is 74%, and the photoelectric conversion efficiency is 16.30%; "with 5CB" is a CsPbI3 solar cell based on 5CB-doped P3HT. The open-circuit voltage of this cell is 1.13V, and the short-circuit current density is 20.66mA / cm 2 , the fill factor is 79%, and the photoelectric conversion efficiency is 18.38%.

[0024] Figure 3 It is the stability of the photoelectric conversion efficiency of CsPbI3 solar cells in air with a humidity of 15-30%RH. "control" is a CsPbI3 solar cell based on pure P3HT, and "with 5CB" is a CsPbI3 solar cell based on 5CB-doped P3HT. Detailed implementation methods

[0025] Example 1:

[0026] Measure 54.2 μL of diisopropyl (acetylacetonato) titanate solution and dissolve it in n-butanol solution to prepare a 0.15M titanium dioxide precursor solution; weigh 78 mg of CsI and 176.7 mg of HPbI3 powder, dissolve them in a mixed solvent of DMF and DMSO with a volume ratio of 4:1, and stir for 4 h under a nitrogen atmosphere to prepare a 0.6M CsPbI3 perovskite solution; weigh 10 mg of P3HT powder, dissolve it in chlorobenzene solvent, and stir for 30 min to prepare a 10 mg / mL P3HT solution. Then add 2.5 μL of 5CB to the P3HT chlorobenzene solution.

[0027] Static spin-coat 70 μL of the prepared n-butanol solution of diisopropyl (acetylacetonato) titanate on the cleaned FTO conductive glass at a spin-coating speed of 2500 rpm for 30 s; then anneal at 125 °C for 5 min; then transfer it to a muffle furnace and heat it to 450 °C at a heating rate of 2 °C / min, and anneal at 450 °C for 60 min to prepare a titanium dioxide thin film as the electron transport layer;

[0028] 45 μL of the prepared CsPbI3 perovskite solution was spin-coated statically on the surface of the prepared titanium dioxide electron transport layer film at a rotation speed of 2000 rpm for 30 s. After spin-coating, it was pre-annealed at 70 °C for 2 min and then annealed at 180 °C for 20 min to form a perovskite film as the photoactive layer.

[0029] 66 μL of the prepared 5CB-doped P3HT solution was spin-coated statically on the surface of the prepared perovskite film at a rotation speed of 3000 rpm for 60 s. After spin-coating, it was annealed at 120 °C for 2 min to form a P3HT:5CB film as the hole transport layer.

[0030] A 100-nm-thick Ag film was evaporated on the surface of the hole transport layer obtained above as the cathode to complete the assembly of the CsPbI3 perovskite solar cell.

[0031] Example 2:

[0032] 72.8 μL of diisopropyl bis(acetylacetonate) titanate solution was measured and dissolved in n-butanol solution to prepare a 0.2 M titanium dioxide precursor solution. 104 mg of CsI and 235.6 mg of HPbI3 powder were weighed and dissolved in a mixed solvent of DMF and DMSO with a volume ratio of 4:1, and stirred in a nitrogen environment for 4 h to prepare a 0.8 M CsPbI3 perovskite solution. 15 mg of P3HT powder was weighed and dissolved in chlorobenzene solvent, stirred for 30 min to prepare a 15 mg / mL P3HT solution, and then 3.5 μL of 5CB was added to the P3HT chlorobenzene solution.

[0033] 70 μL of the prepared n-butanol solution of diisopropyl bis(acetylacetonate) titanate was spin-coated statically on the cleaned FTO conductive glass at a rotation speed of 4000 rpm for 30 s. Then it was annealed at 135 °C for 2 min. After that, it was transferred to a muffle furnace and heated to 450 °C at a heating rate of 2 °C / min, and annealed at 450 °C for 60 min to prepare a titanium dioxide film as the electron transport layer. <U+

[0034] 45 μL of the prepared CsPbI3 perovskite solution was spin-coated statically on the surface of the prepared titanium dioxide electron transport layer film at a rotation speed of 3000 rpm for 30 s. After spin-coating, it was pre-annealed at 70 °C for 5 min and then annealed at 210 °C for 5 min to form a perovskite film as the photoactive layer.

[0035] 66 μL of the prepared P3HT solution doped with 5CB was spin-coated statically on the surface of the prepared perovskite film at a rotation speed of 3000 rpm for 60 s. After spin-coating, it was annealed at 120 °C for 5 min to form a P3HT:5CB film as the hole transport layer.

[0036] An Ag film with a thickness of 80 nm was evaporated on the surface of the obtained hole transport layer as the cathode to complete the assembly of the CsPbI3 perovskite solar cell.

[0037] Example 3:

[0038] 65.1 μL of diisopropyl bis(acetylacetonate) titanate solution was measured and dissolved in n-butanol solution to prepare a 0.18 M titanium dioxide precursor solution. 91 mg of CsI and 206.2 mg of HPbI3 powder were weighed and dissolved in a mixed solvent of DMF and DMSO with a volume ratio of 4:1, and stirred in a nitrogen environment for 4 h to prepare a 0.7 M CsPbI3 perovskite solution. 13 mg of P3HT powder was weighed and dissolved in chlorobenzene solvent, stirred for 30 min to prepare a P3HT solution with a concentration of 13 mg / mL, and then 5 μL of 5CB was added to the P3HT chlorobenzene solution.

[0039] 70 μL of the prepared n-butanol solution of diisopropyl bis(acetylacetonate) titanate was spin-coated statically on the cleaned FTO conductive glass at a spin-coating speed of 3500 rpm for 30 s. Then it was annealed at 130 °C for 3 min. After that, it was transferred to a muffle furnace and heated to 450 °C at a heating rate of 2 °C / min, and annealed at 450 °C for 60 min to prepare a titanium dioxide film as the electron transport layer.

[0040] 45 μL of the prepared CsPbI3 perovskite solution was spin-coated statically on the surface of the prepared titanium dioxide electron transport layer film at a rotation speed of 2500 rpm for 30 s. After spin-coating, it was pre-annealed at 70 °C for 3 min, and then annealed at 200 °C for 10 min to form a perovskite film as the photoactive layer.

[0041] 66 μL of the prepared P3HT solution doped with 5CB was spin-coated statically on the surface of the prepared perovskite film at a rotation speed of 3000 rpm for 60 s. After spin-coating, it was annealed at 120 °C for 3 min to form a P3HT:5CB film as the hole transport layer.

[0042] An Ag film with a thickness of 90 nm was evaporated on the surface of the obtained hole transport layer as the cathode to complete the assembly of the CsPbI3 perovskite solar cell.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention. The present invention is not limited to the embodiments and can be changed within the scope described in the claims. In principle, without departing from the spirit and scope of the technical solutions claimed by the present invention, modifications or substitutions that may be made by those of ordinary skill in the art to the content described in the foregoing embodiments do not exclude the scope claimed by the present invention. The scope claimed by the present invention is defined by the claims.

Claims

1. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, which is characterized in that: The preparation process mainly includes the following steps: Step 1: Prepare a n-butanol solution of diisopropyl bis(acetylacetonato)titanate with a concentration of 0.15 - 0.2 mol / L; Prepare a cesium lead iodide all-inorganic perovskite precursor solution with a concentration of 0.6 - 0.8 mol / L; Prepare a chlorobenzene solution of P3HT with a concentration of 10 - 15 mg / ml, and then add a nematic liquid crystal small molecule to it to prepare the required hole transport layer precursor solution. The nematic liquid crystal small molecule is 4-cyano-4-pentylbiphenyl (5CB); Step 2: Spin-coat the prepared n-butanol solution of diisopropyl bis(acetylacetonato)titanate on a cleaned FTO conductive glass, and then calcine it to prepare a titanium dioxide electron transport layer film; Step 3: Spin-coat the prepared cesium lead iodide all-inorganic perovskite precursor solution on the titanium dioxide electron transport layer prepared in Step 2, and heat-treat it to form a perovskite active layer film; Step 4: Spin-coat the prepared hole transport layer precursor solution on the surface of the perovskite active layer film prepared in Step 3, and heat-treat it to form a hole transport layer film; Step 5: Evaporate a metal electrode on the surface of the hole transport layer film obtained in Step 4 to complete the assembly of the cesium lead iodide all-inorganic perovskite solar cell.

2. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The preparation method of the 0.6 - 0.8 mol / L cesium lead iodide all-inorganic perovskite precursor solution in Step 1 is to dissolve cesium iodide (CsI) and hydrogen lead iodide (HPbI3) in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar mass ratio of 1:

1. The volume ratio of the N,N-dimethylformamide and dimethyl sulfoxide solvents is 4:1 to form a CsPbI3 perovskite precursor solution.

3. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The concentration of the nematic liquid crystal small molecule in the chlorobenzene solution of P3HT in Step 1 is 10 - 20 mM.

4. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The spin-coating method in Step 2 is static spin-coating, with a rotation speed of 2500 - 4000 rpm and a spin-coating time of 30 s. After spin-coating, anneal it at 125 - 135 °C for 2 - 5 min first; then transfer it to a muffle furnace and anneal it at a heating rate of 2 °C / min to 450 °C for 60 min.

5. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The spin-coating method of the perovskite precursor solution in Step 3 is dynamic spin-coating, with a rotation speed of 2000 - 3000 rpm and a spin-coating time of 30 s. After spin-coating, pre-anneal it at 70 °C for 2 - 5 min first, and then anneal it at 180 - 210 °C for 5 - 20 min.

6. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The spin-coating method in Step 4 is static spin-coating, with a rotation speed of 3000 rpm and a spin-coating time of 60 s. After spin-coating, anneal it at 120 °C for 2 - 5 min.

7. A method for preparing a high-performance cesium lead iodide all-inorganic perovskite solar cell by doping a nematic liquid crystal small molecule into a P3HT hole transport layer, characterized in that: The thickness of the metal electrode in Step 5 is 80 - 100 nm; the metal type is any one of gold (Au), silver (Ag), and copper (Cu).

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