Mixed halogen perovskite photovoltaic device based on mesophase regulation and preparation method thereof

Abstract

The invention provides a mixed halogen perovskite photovoltaic device based on mesophase regulation and a preparation method thereof. The device structure sequentially comprises a substrate, a bottom electrode layer, a hole transport layer, a self-assembly molecular layer, a perovskite layer, an interface modification layer, an electron transport layer, a buffer layer and a top electrode layer from bottom to top, when the perovskite layer is prepared, the used perovskite solution is formed by partially replacing DMSO with DMI in the perovskite solution. According to the method, the problem of non-uniform crystallization of halogen is solved through solvent engineering, and in the spin-coating stage, volatilization of DMF and DMSO can stably form a uniform DMI-PbX2 copolymerized intermediate phase. And in the annealing stage, the high-boiling-point DMI is slowly volatilized to promote the synchronous phase change of the DMI-PbX2 adduct. Due to slow crystallization speed and synchronous phase change, a halide phase WBG perovskite thin film with large crystal grains, low defects and uniformity is obtained.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic devices, and more specifically to a mixed-halide perovskite photovoltaic device based on intermediate phase regulation and a preparation method thereof. Background Art

[0002] High-efficiency tandem solar cells (TSCs) have gradually become one of the most promising research directions in the photovoltaic field. Compared with single-junction solar cells, it can absorb the solar spectrum in a wider wavelength range. Organic-inorganic mixed-halide wide-bandgap (WBG) perovskite solar cells are widely used in the top cells of various TSCs, such as perovskite / crystalline silicon, perovskite / perovskite, perovskite / CIGS, perovskite / GaAs, perovskite / organic photovoltaics, etc. Wide-bandgap perovskite solar cells play an important role in enabling narrow-bandgap solar cells to absorb more photons, including providing high transmittance and a wide range of long-wavelength absorption. Therefore, broadening the optical bandgap of the material and ensuring high-quality crystallization of the WBG perovskite solar cell film are two aspects that need to be considered for wide-bandgap perovskite solar cells.

[0003] For wide-bandgap perovskite materials with the ABX3 structure, the main strategy for adjusting the bandgap is to adjust the ratio of bromine to iodine at the X site. The rapid crystallization rate of Br-based perovskites and the asynchronous phase transformation of I, Br perovskites during the crystallization process are the main reasons for the uneven distribution of the halogen phase. Solvent engineering is a common strategy for the crystallization kinetics of pristine perovskite films. Dimethyl sulfoxide (DMSO) is often widely mixed into N,N-dimethylformamide (DMF) solvents to slow down the crystallization rate of the Br-phase component, and DMSO-halide adducts can be formed in a methylammonium (MA)-rich perovskite system. However, according to the molecular interaction theory, it is difficult to form such adducts in a formamidinium (FA)-rich system. For FA-dominated WBG perovskite materials, solvents with strong coordination ability need to be explored to form perovskite precursor adducts, thereby slowing down the crystallization rate of the film and promoting the synchronous phase transformation of the halogen phase. Summary of the Invention

[0004] The purpose of the present invention is to provide a mixed-halide perovskite photovoltaic device based on intermediate phase regulation and a preparation method thereof to solve the problem of asynchronous phase transformation of wide-bandgap perovskite halogens.

[0005] The present invention is achieved as follows:

[0006] A hybrid halide perovskite photovoltaic device based on intermediate phase regulation, whose structure sequentially includes a substrate, a bottom electrode layer, a hole transport layer, a self-assembled molecular layer, a perovskite layer, an interface modification layer, an electron transport layer, a buffer layer, and a top electrode layer from bottom to top; the perovskite solution used in preparing the perovskite layer is formed by partially replacing DMSO with 1,3-dimethyl-2-imidazolidinone (DMI) in the perovskite solution.

[0007] Preferably, the amount of DMI replacing DMSO is 20-160 μL / mL.

[0008] Preferably, the material of the hole transport layer is NiO X , PTAA, Spiro-OMeTAD, fullerene derivatives, and one or more of nitrogen oxides.

[0009] Preferably, the material of the self-assembled molecular layer is at least one of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid, and [2-(3,6-diphenyl-9H-carbazol-9-yl)ethyl].

[0010] Preferably, the material of the perovskite layer is a perovskite material of the ABX3 type; wherein, A is one or more of alkali metal ions and organic ions, the alkali metal ion is Cs ion or Rb ion, and the organic ion includes formamidine; B is Pb ion; X is I and Br.

[0011] Preferably, the interface modification layer is one or more of phenethylammonium iodide, phenethylammonium bromide, and phenethylammonium chloride.

[0012] Preferably, the material of the electron transport layer is C 60 , SnO2, TiO2, PCBM, and one or more of indium tin zinc oxide.

[0013] Preferably, the top electrode layer is a metal electrode or a carbon material electrode; the metal electrode material includes one or more of gold, silver, aluminum, and copper; the carbon material electrode includes one or two of graphite and carbon nanotubes.

[0014] Preferably, the bottom electrode layer is one or more of ITO, FTO, AZO, IZO transparent electrode, graphene-oxide electrode, and oxide-metal-oxide multilayer composite transparent electrode; the oxides in the graphene-oxide electrode and the oxide-metal-oxide multilayer composite transparent electrode include one or more of oxides such as bismuth, molybdenum, tin, titanium, and zinc; and the metal includes one or more of gold, silver, copper, and aluminum.

[0015] The preparation method of the above-mentioned hybrid halide perovskite photovoltaic device based on intermediate phase regulation includes the following steps:

[0016] (1) Deposit a bottom electrode layer on a substrate;

[0017] (2) Prepare a hole transport layer on the bottom electrode layer by spin coating;

[0018] (3) Prepare a self-assembled molecular layer on the hole layer;

[0019] (4) Prepare a perovskite layer on the self-assembled molecular layer: the perovskite is prepared in a mixed solvent of DMF:DMSO:DMI, and the perovskite solution is prepared on the self-assembled molecular layer by an existing process to form a perovskite thin film. Specifically: the perovskite thin film is prepared by methods such as two-step solution method, spin coating method, doctor blade method, spray coating method, etc., and then annealed on a heating table, the annealing temperature is 100 °C, and the time is 60 min;

[0020] (5) Prepare an interface modification layer on the perovskite layer;

[0021] (6) Prepare an electron transport layer on the interface modification layer;

[0022] (7) Prepare a buffer layer on the electron transport layer;

[0023] (8) Prepare a top electrode layer on the buffer layer.

[0024] Preferably, in step (4), the range of x in the solvent DMF:DMSO:DMI (v:v:v = 4:1 - x:x) is 0.2 to 0.8 (the amount of DMI replacing DMSO is 20 - 160 μL / mL).

[0025] The present invention introduces 1,3-dimethyl-2-imidazolidinone (DMI) solvent molecules into the spin coating process to regulate the crystallization process. The C=O in the DMI molecule can form a DMI-PbX2 intermediate phase with the halide salt (PbX2) to anchor the halogen atoms. During the subsequent annealing process, as DMI evaporates, the halogen atoms are released, resulting in halogen co-crystallization. The co-crystallization of halogen atoms and the increase in the migration barrier of halide ions lead to the formation of a uniform mixed halide perovskite thin film. DMI treatment improves carrier transport and inhibits non-radiative recombination, and finally prepares a high-performance wide-bandgap perovskite photovoltaic device. Brief Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the structure of the hybrid halide perovskite photovoltaic device based on intermediate phase regulation provided by the present invention and the realization of a uniform halogen-phase perovskite thin film through the DMI-PbX2 adduct intermediate phase.

[0027] Figure 2It is the J-V curve of the perovskite photovoltaic device prepared in Example 1.

[0028] Figure 3 It is a comparison chart of the photoelectric conversion efficiency, open-circuit voltage, fill factor, and short-circuit current density of the perovskite photovoltaic devices prepared in Examples 1 to 3.

[0029] Figure 4 It is the J-V curve of the perovskite photovoltaic device prepared in Comparative Example 1. Detailed implementation manners

[0031] As Figure 1 shown, the mixed-halide perovskite photovoltaic device based on intermediate phase regulation provided by the present invention includes, from bottom to top in sequence: a substrate, a bottom electrode layer, a hole transport layer, a self-assembled molecular layer, a perovskite layer, an interface modification layer, an electron transport layer, a buffer layer, and a top electrode layer.

[0032] In the prior art, when preparing the perovskite layer, the solvents of the perovskite solution are DMF and DMSO. In the present invention, DMI is used to partially replace DMSO, that is: when preparing the perovskite layer in the present invention, the solvents of the perovskite solution used are DMF, DMSO, and DMI, and the volume ratio of the three is 4:(1 - x):x, where x ranges from 0.2 to 0.8.

[0033] Combined with Figure 1 , in the WBG perovskite system, the present invention adds a solvent molecule DMI to reduce the phenomenon of halide phase separation caused by the faster crystallization rate of Br than I. DMI forms a DMI-PbX2 intermediate phase with PbX2 during the spin-coating process, anchors the halogen, thereby delaying the crystallization of Br, and then synchronizes the phase change of I and Br with the evaporation of DMI during the annealing process, thereby obtaining a high-quality uniform perovskite thin film.

[0034] When preparing the perovskite layer, a perovskite thin film is formed by a two-step solution method, a spin-coating method, a blade-coating method, or a spraying method. The present invention has no special regulations on the preparation of the perovskite layer, and a process well-known to those skilled in the art can be adopted. Preferably, the spin-coating method is adopted, and there are no special restrictions on the remaining methods (such as blade-coating, etc.), and methods well-known in the art can be adopted.

[0035] The perovskite photovoltaic device in the present invention is a wide-bandgap perovskite photovoltaic device; the bandgap of the perovskite photovoltaic device used is 1.65 - 1.8 eV. The present invention has no special requirements for the area of the wide-bandgap perovskite photovoltaic device.

[0036] The substrate selected in the present invention is one or several of conductive glass, flexible PET substrate, flexible PEN substrate, Si-based battery, narrow-bandgap perovskite photovoltaic device, and thin-film battery; if the substrate used is one or several of Si-based battery, narrow-bandgap perovskite photovoltaic device, and thin-film battery, it is a tandem battery; if the substrate used is conductive glass, flexible PET substrate, and flexible PEN substrate, it is a wide-bandgap perovskite photovoltaic device; the present invention has no special limitation on the structures of the selected Si battery, narrow-bandgap perovskite photovoltaic device, and thin-film battery, and the structures well-known to those skilled in the art can be adopted.

[0037] In the present invention, the bottom electrode layer can be selected from one or several of ITO, FTO, AZO, IZO transparent electrodes, graphene-oxide electrode, and oxide-metal-oxide multi-layer composite transparent electrode; the oxides in the graphene-oxide electrode and the oxide-metal-oxide multi-layer composite transparent electrode include one or several of oxides such as bismuth, molybdenum, tin, titanium, and zinc; and the metals include one or several of gold, silver, copper, and aluminum. When two or more of the above electrodes are selected, optimization is required between each electrode layer. The present invention has no special requirement for the thickness of the bottom electrode layer, and the thickness well-known to those skilled in the art can be adopted.

[0038] In the present invention, the bottom electrode layer is prepared by a deposition method, and no special treatment is performed on the deposition process, which is well-known to those skilled in the art. After the deposition process is completed, it is washed successively with a glass cleaning agent, deionized water, and ethanol, and the washing process uses ultrasonic cleaning. Then it is dried with N2 and finally subjected to plasma cleaning treatment.

[0039] In the present invention, the top electrode layer selected is a metal electrode or a carbon material electrode; the metal electrode materials include one or several of gold, silver, aluminum, and copper; the selected carbon material electrodes include one or two of graphite and carbon nanotubes; when the top electrode layer material used is two or more, they can be mixed in any ratio. The present invention has no special requirement for the thickness of the top electrode layer and its position structure in the buffer layer, which is well-known to those skilled in the art.

[0040] In the present invention, the top electrode layer is prepared by a thermal evaporation process, and there is no special limitation on the thermal evaporation process, and the technology well-known to those skilled in the art can be adopted.

[0041] In the present invention, the hole transport layer material used can be NiO X, one or more of PTAA, Spiro-OMeTAD, fullerene derivatives, and nitrogen oxides; when the hole transport layer adopts one or more of the above, there are no special requirements for its ratio, and any ratio can be mixed. And the present invention also has no special requirements for the thickness of the hole transport layer, and the thickness well-known to those skilled in the art can be adopted.

[0042] The present invention has no special regulations for the preparation of the hole transport layer, and the conventional spin coating method can be adopted.

[0043] In the present invention, the material of the perovskite layer is a perovskite material of the ABX3 type; wherein, A is one or more of alkali metal ions and organic ions, the alkali metal is Cs ion or Rb ion, and the organic ion must contain formamidine, which can be formamidine alone, or can include formamidine and methylamine; B is Pb ion; X is I ion and Br ion. The present invention has no special requirements for the thickness of the perovskite layer, and the thickness well-known to those skilled in the art can be adopted.

[0044] The preparation method of the perovskite layer of the present invention is a two-step solution method, an antisolvent method, a vapor deposition method, an evaporation method; the present invention has no special regulations for the above preparation methods, and the methods well-known to those skilled in the art can be adopted.

[0045] In the present invention, the interface modification layer is generally one or more of ammonium salts, phenethylammonium iodide, phenethylammonium bromide, and phenethylammonium chloride. There are no special requirements for its ratio, and there are no special requirements for the thickness either, and the thickness well-known to those skilled in the art can be adopted.

[0046] The electron transport layer material used in the present invention is C 60 , one or more of SnO2, TiO2, PCBM, and zinc tin oxide, etc.; when two or more are selected, there are no special regulations for the ratio, and any ratio can be mixed. Moreover, the present invention has no special requirements for the thickness of the prepared electron transport layer, and the thickness well-known to those skilled in the art can be adopted.

[0047] The present invention aims to partially replace DMSO with 1,3-dimethyl-2-imidazolidinone (DMI) in the solvent formed by DMF and DMSO when preparing the perovskite solution. At the spin coating stage, the volatilization of DMF and DMSO can stably form a uniform DMI-PbX2 intermediate phase. At the annealing stage, the volatilization of DMI promotes the synchronous phase transition of the DMI-PbX2 adduct. Due to the slower crystallization rate and synchronous phase transition, large-grained, low-defect, and uniform mixed halide WBG perovskite thin films are obtained. The DMI-treated perovskite has efficient carrier extraction and inhibits carrier recombination, reducing the V of wide-bandgap perovskite photovoltaic devices ocLoss. Finally, the open-circuit voltage and efficiency of the photovoltaic device are significantly improved, and the method is simple with a high repetition rate.

[0048] The following is a detailed description of the perovskite photovoltaic device of the present invention through examples, but the present invention is not limited to the following examples.

[0049] Example 1

[0050] (1) Glass was used as the substrate, and an ITO layer was deposited on the surface of the used glass. Then, it was ultrasonically cleaned with a cleaning agent, deionized water, and ethanol, dried, and finally plasma cleaned to remove residual organic matter on the surface, and then placed in a glove box for standby.

[0051] (2) NiO was coated on the surface of the ITO layer, the annealing temperature was 110 °C, and the time was 15 min to obtain a hole transport layer. x The annealing temperature was 110 °C and the time was 15 min to obtain a hole transport layer.

[0052] (3) 1 mg of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid was dissolved in 1 mL of absolute ethanol. After complete dissolution, the solution was reserved; the obtained solution was coated on the surface of the hole transport layer and annealed. The annealing temperature was 100 °C and the time was 10 min to obtain a self-assembled molecular layer.

[0053] (4) The perovskite film was prepared by the anti-solvent method. 1.2 mmol of FAI, 0.225 mmol of CsI, 0.075 mmol of DMAI, 0.825 mmol of PbI2, 0.675 mmol of PbBr2, and 0.32 mmol of MACl were mixed and dissolved in 1 mL of DMF, DMSO, and DMI solvents (the volume ratio of the solvents was 4:0.6:0.4, that is, the amount of DMI replacing DMSO was 80 μL / mL) to obtain a perovskite solution; 30 μL of the perovskite solution was dropped on the self-assembled molecular layer, and then spin-coated at a speed of 5000 rpm for 40 s to form a film. Then, 120 μL of the anti-solvent was dropped in the last 10 s, and annealed on a heating table at 100 °C for 60 min to obtain a perovskite layer (the system was FA 0.8 Cs 0.15 DMA 0.05 Pb(I 0.7 Br 0.3 )3).

[0054] (5) 3 mg of phenethylammonium iodide was dissolved in 1 mL of isopropanol. After complete dissolution, the solution was reserved; the obtained solution was coated on the surface of the perovskite layer and annealed. The annealing temperature was 100 °C and the time was 10 min to obtain an interface modification layer.

[0055] (6) C was evaporated on the interface modification layer 60, the evaporation thickness is 15 - 40 nm to form an electron transport layer.

[0056] (7) Evaporate BCP on the prepared electron transport layer with an evaporation thickness of 8 - 12 nm to obtain a buffer layer.

[0057] (8) Finally, prepare the Ag electrode to obtain a perovskite photovoltaic device.

[0058] Place the obtained perovskite photovoltaic device under a standard sunlight (AM 1.5, 100 mW / cm 2 ), and measure the optoelectronic performance of the device. The J-V curve is as Figure 2 shown. The measured short-circuit current density of the perovskite photovoltaic device is 19.75 mA / cm 2 , the fill factor is 82.07%, the open-circuit voltage is 1.32 V, and the photoelectric conversion efficiency is 21.42%.

[0059] Example 2

[0060] Compared with Example 1, in this example, the volume ratio of DMF, DMSO, and DMI solvents is 4:0.8:0.2, that is, the amount of DMI replacing DMSO is 40 μL / mL, and the rest are the same as in Example 1.

[0061] Example 3

[0062] Compared with Example 1, in this example, the volume ratio of DMF, DMSO, and DMI solvents is 4:0.4:0.6, that is, the amount of DMI replacing DMSO is 120 μL / mL, and the rest are the same as in Example 1.

[0063] Prepare different samples according to the processes in Examples 1 - 3, and test the photoelectric conversion efficiency, open-circuit voltage, fill factor, and short-circuit current density of the obtained samples. The test results are as Figure 3 shown. From Figure 3 it can be seen that the average values of the photoelectric conversion efficiency of the perovskite photovoltaic devices prepared according to Examples 1 - 3 are 20.8%, 19.4%, and 18.3% in sequence, the average values of the open-circuit voltage are 1.31 V, 1.29 V, and 1.26 V in sequence, the average values of the fill factor are 82%, 80.9%, and 80.2% in sequence, and the average values of the short-circuit current density are 19.3 mA / cm 2 , 18.5 mA / cm 2 , and 18 mA / cm 2 . Among them, the perovskite photovoltaic device in Example 1 has better repeatability and the best efficiency, mainly due to the significant increase in the short-circuit current. When DMI replaces DMSO by 120 μL / mL, the V OC of the device decreases significantly.

[0064] Comparative Example 1

[0065] Referring to Example 1, the difference is that after obtaining the self-assembled molecular layer, a perovskite layer is spin-coated on the self-assembled molecular layer. The preparation process of the perovskite layer is as follows: 1.2 mmol of FAI, 0.225 mmol of CsI, 0.075 mmol of DMAI, 0.825 mmol of PbI2, 0.675 mmol of PbBr2, and 0.32 mmol of MACl are mixed and dissolved in 1 mL of DMF and DMSO solvents (the volume ratio of the solvents is 4:1) to obtain a perovskite solution; the rest are the same as in Example 1. That is to say, this comparative example is a control group without DMI solvent.

[0066] Comparative Example 2

[0067] Referring to Example 1, the difference is that after obtaining the self-assembled molecular layer, a perovskite layer is spin-coated on the self-assembled molecular layer. The preparation process of the perovskite layer is as follows: 1.2 mmol of FAI, 0.225 mmol of CsI, 0.075 mmol of DMAI, 0.825 mmol of PbI2, 0.675 mmol of PbBr2, and 0.32 mmol of MACl are mixed and dissolved in 1 mL of DMF and DMI solvents (the volume ratio of the solvents is 4:1) to obtain a perovskite solution; the rest are the same as in Example 1. That is to say, this comparative example is a control group in which DMI completely replaces DMSO.

[0068] The perovskite photovoltaic devices obtained in Comparative Examples 1 and 2 are irradiated under a standard solar intensity (AM 1.5, 100 mW / cm 2 ), and the optoelectronic properties of the perovskite photovoltaic devices are tested. The J-V curves are as Figure 4 shown. The open-circuit voltages of the perovskite photovoltaic devices obtained in Comparative Documents 1 and 2 are both 1.26 V, the fill factors are 80.85% and 78.16% respectively, and the short-circuit current densities are 18.32 mA cm -2 and 17.81 mA cm -2 , and the photoelectric conversion efficiencies are 18.52% and 17.55% respectively.

[0069] What is described above is only the optimal implementation of the present invention. In particular, for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications are regarded as the protection scope of the present invention.

Claims

1. A hybrid halogen perovskite photovoltaic device based on mesophase regulation, whose structure includes, from bottom to top, a substrate, a bottom electrode layer, a hole transport layer, a self-assembled molecular layer, a perovskite layer, an interface modification layer, an electron transport layer, a buffer layer and a top electrode layer; wherein: The solvents of the perovskite solution used in preparing the perovskite layer are DMF, DMSO and DMI, and the volume ratio of the three is 4:1-x:x; wherein the range of x is 0.2 to 0.

8.

2. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The substrate is one or more of conductive glass, a flexible PET substrate, a flexible PEN substrate, a Si bottom battery, a narrow bandgap perovskite photovoltaic device and a thin film battery.

3. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The hole transport layer material is NiO X , PTAA, Spiro-OMeTAD, fullerene derivatives and nitrogen oxides.

4. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The self-assembled molecular layer material is at least one of [2-(9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid and [2-(3,6-diphenyl-9H-carbazole-9-yl)ethyl].

5. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The material of the perovskite layer is an ABX3 type perovskite material; wherein A is one or more of alkali metal ions and organic ions, the alkali metal ions are Cs ions or Rb ions, and the organic ions include formamidine; B is Pb ions; and X is I and Br.

6. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The interface modification layer is one or more of phenethylammonium iodide, phenethylammonium bromide and phenethylammonium chloride.

7. The hybrid halogen perovskite photovoltaic device based on mesophase regulation according to claim 1, characterized in that: The electron transport layer material is C 60 , SnO2, TiO2, PCBM and zinc tin oxide or more.

8. A method for preparing a mixed halogen perovskite photovoltaic device based on mesophase regulation, characterized in that: The steps include: (1) depositing a bottom electrode layer on a substrate; (2) preparing a hole transport layer on the bottom electrode layer by spin coating; (3) preparing a self-assembled molecular layer on the hole layer; (4) Preparing a perovskite layer on the self-assembled molecular layer: first, the perovskite is formed into a perovskite solution in a mixed solvent of DMF, DMSO and DMI, and the perovskite solution is formed into a perovskite film on the self-assembled molecular layer by a two-step solution method, a spin coating method, a doctor blade coating method or a spray coating method; in the mixed solvent of DMF, DMSO and DMI, the volume ratio of the three is 4:1-x:x; wherein x ranges from 0.2 to 0.8; (5) preparing an interface modification layer on the perovskite layer; (6) preparing an electron transport layer on the interface modification layer; (7) preparing a buffer layer on the electron transport layer; (8) Prepare a top electrode layer on the buffer layer.

9. The method for preparing a mixed halogen perovskite photovoltaic device based on mesophase regulation according to claim 8, characterized in that: The band gap of perovskite photovoltaic devices is 1.65~1.8eV.

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