CN113540362A

CN113540362A - Perovskite solar cell without electron transport layer and preparation method thereof

Info

Publication number: CN113540362A
Application number: CN202110740954.6A
Authority: CN
Inventors: 吴聪聪; 段晨晖; 王世敏; 董兵海; 赵丽; 李静
Original assignee: Hubei University
Current assignee: Hubei University
Priority date: 2021-06-30
Filing date: 2021-06-30
Publication date: 2021-10-22
Anticipated expiration: 2041-06-30
Also published as: CN113540362B

Abstract

The invention belongs to the field of perovskite solar cells, and particularly relates to a perovskite solar cell without an electron transport layer and a preparation method thereof. Coating a perovskite light absorption layer precursor on the surface of the substrate in an oxygen-free and water-free environment, and annealing to obtain the perovskite light absorption layer; the perovskite light absorption layer precursor comprises a perovskite component, imidazole cationic ionic liquid and an organic solvent; preparing a hole transport layer on the surface of the perovskite light absorption layer; and finally depositing a metal electrode on the surface of the hole transport layer to obtain the perovskite solar cell without the electron transport layer. By adding imidazole cationic ionic liquid into the precursor, the migration capability of the current carrier of the perovskite light absorption layer is improved, so that the performance of the device is improved, and the highest efficiency of the battery reaches more than 16%. The preparation method of the invention not only ensures higher battery efficiency, but also simplifies the preparation process, and brings great convenience for practical application.

Description

Perovskite solar cell without electron transport layer and preparation method thereof

Technical Field

The invention belongs to the field of perovskite solar cells, and particularly relates to a perovskite solar cell without an electron transport layer and a preparation method thereof.

Background

Organic-inorganic halide perovskite materials are receiving a great deal of attention due to their excellent absorption coefficient, high carrier mobility, long carrier lifetime and good photovoltaic properties. The power conversion of organic-inorganic halide Perovskite Solar Cells (PSCs) has increased from 3.9% in 2009 to the recently reported 25.2%, already exceeding most other photovoltaic devices. The common structure of the high efficiency devices reported today is to place a perovskite layer between two carrier transport layers, one to block electron transport holes, i.e. the Hole Transport Layer (HTL), and the other to block holes and transport electrons, i.e. the Electron Transport Layer (ETL), with a metal electrode on top.

For the high-performance devices at present, a p-i-n structure is generally adopted, and a suitable electron transport material and a suitable hole transport material have a decisive effect on the performance of the devices. For the mesoporous structure commonly used at present, titanium dioxide (TiO) is generally used₂) A mesoporous layer and a dense layer. TiO 2₂The mesoporous layer requires high temperature sintering to remove the trapped TiO₂Organic matter in the slurry to raise TiO₂The crystallinity of (a). In planar structures, with TiO₂As ETL is a very common structure, but TiO is found₂Has a charge barrier with perovskite, so that the charge transfer efficiency of the interface is low, thereby leading to the large accumulation of the interface charge, and TiO is deposited₂High temperature sintering is required, which increases the cost, and TiO₂ETL is capable of inducing degradation of perovskite thin films under light. Due to TiO₂While many researchers are looking for alternatives to work at low temperatures, some have found alternatives to TiO₂Zinc oxide (ZnO) and tin oxide (SnO)₂) Fullerene derivatives, and the like. Although effective developments have been made in using these materials for ETL, these materials themselves have some negative effects as ETL, so it is an urgent need to find a method to remove ETL and maintain the efficiency of the battery.

Patent document CN111710780A discloses a method for preparing a cathode in-situ modified perovskite solar cell without an electron transport layer, which adopts methylamine acetate or methylamine formate ionic liquid as a solvent to prepare a perovskite precursor, and although the perovskite solar cell without the electron transport layer is prepared, the method is only suitable for MAPbI₃The unitary perovskite solar cell has low universality, and in addition, the ionic liquid methylamine acetate or methylamine formate adopted by the unitary perovskite solar cell has high cost, and the market price is hundreds of yuan per milliliter, so that the method has high cost and cannot be produced and applied in a large scale.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an electron transport layer-free perovskite solar cell prepared by using imidazole cationic ionic liquid as a perovskite layer additive, which is suitable for perovskite solar cells and solves the problems that the electron transport layer-free perovskite solar cell in the prior art is only suitable for one perovskite material, and the ionic liquid is large in dosage, high in cost and incapable of being produced and applied in a large scale.

In order to achieve the above object, the present invention provides a method for preparing a perovskite solar cell without an electron transport layer, comprising the steps of:

(1) preparing a perovskite film on a substrate to obtain a perovskite light absorption layer; the method specifically comprises the following steps:

coating a perovskite light absorption layer precursor on the surface of the substrate in an oxygen-free and water-free environment, and annealing to obtain the perovskite light absorption layer; the perovskite light absorption layer precursor comprises a perovskite component, imidazole cationic ionic liquid and an organic solvent;

(2) preparing a hole transport layer on the surface of the perovskite light absorption layer;

(3) and depositing a metal electrode on the surface of the hole transport layer.

Preferably, the substrate is cleaned and UV-treated FTO glass, ITO glass or a flexible ITO conductive substrate, and the flexible ITO conductive substrate can be ITO/PEN or ITO/PET.

In the preferred scheme, the substrate is sequentially placed into deionized water, acetone, isopropanol and ethanol for ultrasonic cleaning to obtain a cleaned substrate; and (4) treating the cleaned substrate in a UV-zone to obtain a cleaned and UV-treated substrate.

In the preferred scheme, the substrate is sequentially placed into deionized water, acetone, isopropanol and ethanol for ultrasonic cleaning and cleaning for 20-30 min; and treating the cleaned substrate in a UV-zone for 30-40 min.

In a preferred embodiment, the perovskite component is an FA-based (amidino) perovskite component.

In a preferred scheme, the perovskite component is an amidino binary or ternary perovskite component.

In a preferred embodiment, the perovskite component is a ternary perovskite component comprising Cs (cesium), FA (formamidine) and MA (methylamine).

In a preferred embodiment, the perovskite light absorption layer precursor contains 1 to 1.3mol of the perovskite component per ml of the solvent.

In a preferred embodiment, the imidazole cationic ionic liquid is one or more of EMIMPF6, DMIMPF6 and BMIMBF 4; the molar weight of the imidazole cationic ionic liquid in the perovskite light absorption layer precursor is 0.03-0.1% of that of the perovskite component.

In a preferred embodiment, the organic solvent is a mixture of DMF and DMSO, wherein the volume ratio of DMF to DMSO is in the range of 3-5: 1.

In the preferred scheme, the perovskite light absorption layer precursor is spin-coated on the surface of the substrate in the step (1), the spin-coating is divided into two stages, and the first stage is spin-coating at the rotation speed of 1000-1500rpm for 10-15 s; the second stage of spin coating is spin coating at 4000-.

In the preferable scheme, the annealing temperature in the step (1) is 100-150 ℃, and the annealing time is 10-40 min.

In a preferred embodiment, the Hole Transport Layer (HTL) is made of spiro-omtad (tetrakis [ N, N-bis (4-methoxyphenyl) amino ] spirobifluorene), P3HT (polymer of 3-hexylthiophene), or PTAA (poly (triarylamine)).

Preferably, a spirol-OMeTAD solution is coated on the perovskite light absorption layer, and is dried and oxidized to obtain a spirol-OMeTAD thin film, namely the hollow transmission layer.

In a preferred scheme, the concentration of the spiro-OMeTAD in the spiro-OMeTAD solution is 73-84 mg/ml; the coating adopts a spin coating mode, the spin coating speed is 3000-4000rpm, and the spin coating time is 20-30 s; the oxidation time is 10-12 hours.

In a preferred embodiment, the thickness of the deposited metal electrode is 60-80 nm.

In a preferred embodiment, the metal electrode is a gold electrode or a silver electrode.

According to another aspect of the present invention, there is provided an electron transport layer-free perovskite solar cell comprising a substrate layer, a perovskite light absorption layer, a hole transport layer and an electrode, which are sequentially stacked, wherein the perovskite light absorption layer comprises a perovskite component and an imidazolium cationic ionic liquid, wherein the molar amount of the imidazolium cationic ionic liquid is 0.03 to 0.1% of the molar amount of the perovskite component.

In a preferred embodiment, the perovskite component is a FA-based perovskite component.

Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

(1) the invention provides a preparation method of a perovskite solar cell without an electron transport layer, which is characterized in that imidazole cationic ionic liquid is added into a precursor of a perovskite light absorption layer as an additive to passivate defects in a perovskite body and improve the mobility of current carriers, the morphology of the perovskite is optimized, the size of crystal grains is enlarged, the perovskite solar cell without the electron transport layer is prepared, and the highest efficiency of the cell reaches more than 16%.

(2) According to the preparation method of the perovskite solar cell without the electron transmission layer, the imidazole cationic ionic liquid with low addition cost is added, the addition amount is small, the preparation cost of the existing perovskite solar cell without the electron transmission layer is reduced, and the preparation process is simplified. The preparation method is particularly suitable for FA-based perovskite solar cells, and the application range of the perovskite solar cells without the electron transport layer is expanded.

(3) According to the perovskite solar cell without the electron transport layer, the perovskite light absorption layer contains imidazole cationic ionic liquid, the perovskite defect is passivated, the morphology of perovskite is optimized, the grain size of perovskite is improved, and the mobility of a current carrier is improved.

Drawings

Fig. 1 is a structure of a perovskite solar cell in example 1;

FIG. 2 is an I-V curve of the assembled electron transport layer-free planar perovskite solar cell of example 1; wherein: voltage (V) on the X-axis, and photocurrent density (mA-cm) on the Y-axis^-2)；

FIG. 3 is an I-V curve of the assembled electron transport layer-free planar perovskite solar cell of comparative example 1; wherein: voltage (V) on the X-axis, and photocurrent density (mA-cm) on the Y-axis^-2)；

Fig. 4 is a photoluminescence spectrum of a planar perovskite solar cell without an electron transport layer as the addition amount of an ionic liquid additive increases, wherein: the X axis is the wavelength and the Y axis is the peak intensity;

FIG. 5 is a schematic illustration of the passivation defect mechanism of a perovskite solar cell prepared according to an embodiment of the present invention;

FIG. 6 is a PbI perovskite solar cell prepared in example 1₂Infrared spectrum of bonding in ionic liquids. Wherein: x-axis Wavenumber is the number of waves (cm)^-1) Y axisTransmission is the transmittance;

fig. 7 is an XPS spectrum of the Pb4f orbit of the perovskite solar cell prepared in example 1. Wherein: the X axis is binding energy, and the Y axis is peak strength;

fig. 8 is an XPS spectrum of the I3d orbits of the perovskite solar cell prepared in example 1. Wherein: the X axis is binding energy, and the Y axis is peak strength;

fig. 9 is a space charge limited current map of the perovskite thin film in example 1. Wherein: voltage (V) on the X-axis, and photocurrent density (mA-cm) on the Y-axis^-2)；

Fig. 10 is a schematic scanning electron microscope of the perovskite thin film prepared in example 1, the left figure is a picture without adding an ionic liquid, and the right figure is a picture with an ionic liquid.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

Step 100: for FTO (fluorine-doped SnO)₂Conductive glass) substrate for cleaning

Step 101: placing the FTO substrate in an ultrasonic cleaning instrument, ultrasonically cleaning the FTO substrate by using deionized water, acetone, isopropanol and ethanol in steps, wherein the cleaning time of each step is 30min, and blowing air for drying for later use;

step 102: treating the cleaned FTO substrate by using UV-zone, and placing the FTO substrate in an ozone atmosphere environment for 30 min;

step 200: preparation of the absorbent layer

Step 201: mixing 1.05mol of FAI and 1.1mol of PbI₂、0.185molMABr、0.185molPbBr₂0.05mol of EMIMPF6, MACl with a mass of 15mg dissolved in 1ml of DMF in a volume ratio DMSO 4: 1, stirring at room temperature until the mixed solvent is completely dissolved to obtain a binary perovskite precursor solution; dissolving 1.5mol CsI in 1ml DMSO, and stirring uniformly to obtain C_SDMSO solution of I; take 50. mu.l of C_SDissolving the DMSO solution of I in the obtained binary perovskite precursor solution to obtain a perovskite light absorption layer precursor solution;

step 202: spin-coating the prepared precursor solution on an FTO substrate treated by UV-zone in step 102, and preparing a film by using a two-step spin-coating method, wherein the spin speeds and the spin times of the first step and the second step are 1000rpm, 10s, 3000rpm and 30s respectively;

step 203: 200 microliter of anti-solvent chlorobenzene is dripped 10s before the spin coating is finished;

step 204: placing the film prepared in the step 203 in a heating table for annealing, wherein the annealing temperature and the annealing time are respectively 150 ℃ for 10min and 100 ℃ for 30 min;

step 300: preparation of hole transport layer

Step 301: spin-coating a spiro-OMeTAD (tetra [ N, N-di (4-methoxyphenyl) amino ] spirobifluorene) hole transport layer on the prepared absorption layer, wherein the concentration of the spiro-OMeTAD is 73mg/ml, the rotating speed of the spin-coating is 4000rpm/min, and then oxidizing for 10 hours in a dry environment;

step 400: preparation of Metal electrodes

Step 401: the film treated with 301 was subjected to thermal evaporation gold plating, and 80nm gold electrodes were evaporated.

The perovskite structure prepared in this example is shown in fig. 1, where AU in fig. 1 represents a gold electrode, HTL represents a spiro-OMeTAD hole transport layer, pervoskite represents a perovskite light absorption layer, and FTO represents an FTO substrate. The I-V curve of the perovskite device is shown in fig. 2, and the various parameters of the perovskite device are shown in table 1:

table 1 various parameters of the perovskite device prepared in example 1

Comparative example 1

Step 100: cleaning of FTO substrates

Step 101: placing the FTO substrate in an ultrasonic cleaning instrument, ultrasonically cleaning the FTO substrate by using deionized water, acetone, isopropanol and ethanol in steps, wherein the cleaning time of each step is 20-30min, and blowing air for drying for later use;

step 102: treating the cleaned FTO substrate by using UV-zone, and placing the FTO substrate in an ozone atmosphere environment for 40 min;

step 200: preparation of the absorbent layer

Step 201: mixing 1.05mol of FAI and 1.1mol of PbI₂、0.185molMABr、0.185molPbBr₂MACl with a mass of 15mg was dissolved in 1ml of DMF: DMSO ═ 4: 1, stirring at room temperature until the mixed solvent is completely dissolved to obtain a binary perovskite precursor solution; dissolving 1.5mol of CsI in 1ml of DMSO, and uniformly stirring to obtain a DMSO solution of CSI; dissolving 50 microliters of DMSO solution of CSI in the obtained binary perovskite precursor solution to obtain a perovskite light absorption layer precursor solution;

step 300: preparation of hole transport layer

Step 301: spin-coating a spiro-OMeTAD hole transport layer on the prepared absorption layer, wherein the concentration of the spiro-OMeTAD is 73mg/ml, the rotating speed of the spin-coating is 4000rpm/min, and then oxidizing for 10 hours in a dry environment;

step 400: preparation of Metal electrodes

Step 401: the film treated in 301 was subjected to thermal evaporation coating, and 80nm metal electrodes were deposited by evaporation.

The I-V curve of the perovskite device prepared in this example is shown in fig. 3, and the parameters of the prepared perovskite device are shown in table 2:

table 2 various parameters of the perovskite device prepared in example 2

The highest efficiency of the device was 13.5% without the addition of the ionic liquid emipf 6, which is much lower than the device modified with emipf 6 in example 1.

TABLE 3 various parameters of different ionic liquid concentration perovskite devices

Table 3 and fig. 4 are schematic photoluminescence diagrams of devices obtained by changing the concentration of the added ionic liquid EMIMPF6 under the same conditions as in example 1, and it can be seen that, as the content of EMIMPF6 increases (the curve in the figure gradually increases from top to bottom corresponding to the content of EMIMPF 6), the peak value becomes lower and lower, and the addition of the ionic liquid accelerates charge transfer, and reduces charge recombination inside the perovskite and at the interface.

Fig. 5 is a schematic diagram of the mechanism of introducing defects in a passivated perovskite light absorption layer into the ionic liquid in the perovskite solar cell prepared in example 1. N in the ionic liquid can be coordinated with Pb which is coordinated in the perovskite so as to achieve the effect of passivating the defect.

FIG. 6 shows PbI in example 1₂Infrared spectrum of bonding in ionic liquids. Wherein: x-axis Wavenumber is the number of waves (cm)^-1) The transmittance on the Y axis is the transmittance, and the peak of the C-N bond is shifted from the infrared spectrogram, which is probably caused by the weakening of the C-N bond in the ionic liquid due to the combination of N in the ionic liquid and the uncoordinated Pb in the perovskite.

Fig. 7 is an XPS spectrum of the Pb4f orbit in example 1. Wherein: the X axis is binding energy, and the Y axis is peak strength; it can be seen from the XPS spectrum that the binding energy of Pb tends to decrease after the ionic liquid is added, which is probably because the coordination of N and Pb leads to the breakage of I-Pb bond, thereby affecting the binding energy of Pb.

FIG. 8 is an XPS spectrum of the I3d orbits in example 1. Wherein: the X axis is binding energy, and the Y axis is peak strength; from XPS spectra, it can be seen that the binding energy of I tends to decrease after the ionic liquid is added, which is probably because the coordination of N and Pb leads to the breakage of I-Pb bond, thereby affecting the binding energy of I.

Fig. 9 is a space charge limited current map of the perovskite thin film in example 1. Wherein: voltage (V) on the X-axis, and photocurrent density (mA-cm) on the Y-axis^-2) (ii) a As can be seen from the figure, the defect filling limit voltage of the added ionic liquid is far less than that of the non-added ionic perovskite thin film, which shows that the defect state density is effectively reduced by adding the ionic liquid.

FIG. 10 is a schematic scanning electron microscope of the perovskite thin film prepared in example 1, the left image is a picture without ionic liquid added, and the right image is a picture with ionic liquid added. As can be seen from the figure, after the ionic liquid is added, the surface appearance of the perovskite thin film is obviously improved, and the grain size is obviously increased.

According to the invention, the ionic liquid EMIMPF6 is added into the perovskite precursor, experiments prove that the defect of the perovskite light absorption layer can be passivated, the mobility of a current carrier is improved, the morphology of the perovskite is optimized, the grain size is enlarged, the cost is reduced, the preparation process is simplified, and the requirement of high efficiency is also met, so that the preparation method is a simple perovskite structure preparation method, and a feasible thought is provided for the future commercial road development.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A preparation method of a perovskite solar cell without an electron transport layer is characterized by comprising the following steps:

2. The method of claim 1, wherein the substrate is a cleaned and UV treated FTO glass, ITO glass, or flexible ITO conductive base.

3. The production method according to claim 1, wherein the perovskite component is an FA-based perovskite component.

4. The preparation method of claim 1, wherein the imidazole cationic ionic liquid is one or more of EMIMPF6, DMIMPF6 and BMIMBF 4;

the molar weight of the imidazole cationic ionic liquid in the perovskite light absorption layer precursor is 0.03-0.1% of that of the perovskite component.

5. The method of claim 1, wherein the organic solvent is a mixture of DMF and DMSO, wherein the volume ratio of DMF to DMSO is in the range of 3-5: 1.

6. The method according to claim 1, wherein the step (1) spin-coats the perovskite light absorption layer precursor on the surface of the substrate in two stages, the first stage of spin-coating is spin-coating at a rotation speed of 1000 and 1500rpm for 10-15 s; the second stage of spin coating is spin coating at 4000-.

7. The method as claimed in claim 1, wherein the annealing temperature in step (1) is 100-150 ℃ and the annealing time is 10-40 min.

8. The production method according to claim 1, wherein the hole transport layer of step (2) is made of a material selected from the group consisting of spiro-OMeTAD, P3HT and PTAA.

9. The method of claim 1, wherein the thickness of the deposited metal electrode of step (3) is 60 to 80 nm.

10. The perovskite solar cell without the electron transport layer is characterized by comprising a substrate layer, a perovskite light absorption layer, a hole transport layer and an electrode which are sequentially stacked, wherein the perovskite light absorption layer comprises a perovskite component and an imidazolium cationic ionic liquid, and the molar weight of the imidazolium cationic ionic liquid is 0.03-0.1% of that of the perovskite component.