A trans-perovskite solar cell and a preparation method thereof

Abstract

The application relates to the technical field of photovoltaic cells, in particular to a transverse perovskite solar cell and a preparation method thereof. The structure of the transverse perovskite solar cell comprises, from top to bottom, a metal electrode, an electron transport layer, a perovskite active layer, a hole transport layer and a substrate glass, and the perovskite active layer contains tris(2,2,2-trifluoroethyl) phosphate. The tris(2,2,2-trifluoroethyl) phosphate molecules are introduced into the perovskite active layer, the molecules are dispersed on the surface of the perovskite and in the perovskite, the perovskite crystallization is regulated, the film defects of the perovskite layer can be effectively reduced, and high-quality light-absorbing materials and high-performance transverse perovskite cells can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, in particular to a transverse perovskite solar cell and a preparation method thereof. BACKGROUND

[0002] In recent years, perovskite solar cells (PerSCs) with inverted structure have attracted extensive attention due to their simple fabrication process, compatibility with tandem devices and reliable stability. However, due to the high-temperature annealing and rapid crystallization process in the preparation process, a large number of defects inevitably exist at the interface between the perovskite thin film and the charge transport layer, which will cause serious non-radiative recombination at the interface. The influence of defects on PerSCs is as follows:

[0003] (1) The defects mainly exist on the surface of the perovskite, which are easy to cause deep traps in the band gap, and are usually non-radiative recombination centers for reducing the open-circuit voltage (V OC ) output;

[0004] (2) Under the action of light, heat or electric stress, these defects will reduce the ion migration energy barrier, thereby reducing the stability of the perovskite thin film or limiting the transfer of charge carriers;

[0005] (3) Under the action of an external electric field, these defects will cause the enhancement of the interface capacitance, and the charge carriers can be easily charged and discharged, thereby increasing the hysteresis of the perovskite.

[0006] The prior art often uses an interface modification layer to passivate the perovskite thin film to reduce defects, but there is a problem that the action of the passivation molecules is relatively single, or only the surface of the thin film can be passivated but not the inside of the perovskite. Therefore, how to further reduce the defects of the thin film and reduce the non-radiative recombination at the interface is very important for developing high-efficiency and stable commercial perovskite solar cells. SUMMARY

[0007] In order to solve the defects in the prior art, the present application provides a transverse perovskite solar cell and a preparation method thereof. By introducing tri(2,2,2-trifluoroethyl) phosphate molecules into the perovskite active layer, the molecules are dispersed on the surface of the perovskite and inside the perovskite, so as to control the perovskite crystallization. The film defects of the perovskite layer can be effectively reduced to obtain high-quality light-absorbing materials and high-performance transverse perovskite cells.

[0008] To achieve the above object, the present application adopts the following technical scheme:

[0009] In a first aspect, the present application provides a trans-perovskite solar cell, the structure of the trans-perovskite solar cell from top to bottom comprises a metal electrode, an electron transport layer, a perovskite active layer, a hole transport layer and a substrate glass, and the perovskite active layer contains tris(2,2,2-trifluoroethyl) phosphate.

[0010] Preferably, the metal electrode material is selected from any one of gold, silver, copper, aluminum.

[0011] Preferably, the electron transport layer material is selected from any one or several of PCBM, BCP.

[0012] Preferably, the perovskite active layer material is selected from one or several of formamidinium salt, lead halide salt.

[0013] Preferably, the hole transport layer material is MeO-2PACz.

[0014] Preferably, the substrate glass material is ITO or FTO.

[0015] In a second aspect, the present application provides a preparation method of a trans-perovskite solar cell, comprising the following steps:

[0016] S1, pretreating a substrate glass;

[0017] S2, depositing a hole transport layer on the substrate glass;

[0018] S3, depositing a perovskite active layer on the hole transport layer: preparing a perovskite precursor solution and an anti-solvent containing tris(2,2,2-trifluoroethyl) phosphate, spin-coating the perovskite precursor solution on the hole transport layer, starting to drop and drop the anti-solvent within the last 5s of spin-coating, and then performing annealing to obtain the perovskite active layer;

[0019] S4, depositing an electron transport layer on the perovskite active layer;

[0020] S5, depositing a metal electrode on the electron transport layer.

[0021] Preferably, the S1 specifically comprises: washing the substrate glass and then treating it with ozone. In some embodiments of the present application, the substrate glass is sequentially subjected to ultrasonic treatment with detergent, deionized water, isopropanol, acetone and anhydrous ethanol, and then dried with nitrogen for standby, and then treated with ozone.

[0022] Preferably, the substrate glass material is ITO or FTO.

[0023] Preferably, the S2 specifically comprises: dissolving the hole transport layer material in a solvent and depositing it on the substrate glass.

[0024] Preferably, the concentration of the hole transport layer material is 0.5 mg / mL.

[0025] Preferably, the hole transport layer material is MeO-2PACz.

[0026] Preferably, in S3, the preparation of the precursor solution is: dissolving the perovskite active layer material in a solvent, the solvent being DMF and DMSO in a volume ratio of 4:1.

[0027] Preferably, the perovskite active layer material is selected from one or several of formamidinium salt, lead halide salt.

[0028] Preferably, in S3, the preparation of the anti-solvent is: dissolving tris(2,2,2-trifluoroethyl) phosphate in anisole.

[0029] Preferably, the concentration of tris(2,2,2-trifluoroethyl) phosphate in the anti-solvent of S3 is 10-20 μL / ml. Exemplarily, the concentration of tris(2,2,2-trifluoroethyl) phosphate in the anti-solvent of S3 is any one of 10, 15, 18, 20 μL / ml or a value between any two of them.

[0030] Preferably, in S3, the process of spin-coating the perovskite precursor solution and dropwise adding the anti-solvent is specifically: two-step spin-coating of the perovskite precursor solution on the hole transport layer, the two-step spin-coating parameters being rotation speed 1000 rad / min, acceleration 500 rad / min, spin-coating time 10 s and rotation speed 4500 rad / min, acceleration 3000 rad / min, spin-coating time 40 s, at the 45th second of the total time, starting to dropwise add the anti-solvent solution for extraction, extraction time being 2 s.

[0031] Preferably, the annealing temperature in S3 is 150℃, and the time is 30 min.

[0032] Preferably, S4 is specifically: dissolving the electron transport layer material in a solvent and depositing on the surface of the perovskite active layer.

[0033] Preferably, the concentration of the electron transport layer material is 0.5-30 mg / ml.

[0034] Preferably, the electron transport layer material is selected from any one or several of PCBM, BCP.

[0035] Preferably, the metal electrode material is selected from any one of gold, silver, copper, aluminum.

[0036] The beneficial effects of the present application are:

[0037] The trans perovskite solar cell structure of the present application introduces tris(2,2,2-trifluoroethyl) phosphate molecules into the perovskite active layer, and the molecules are dispersed on the surface and inside the perovskite, which can regulate the perovskite crystallization, thereby effectively reducing the film defects of the perovskite layer, improving the average carrier lifetime of the perovskite film, reducing the interface recombination loss of the device, and reducing the roughness of the perovskite film, improving the energy level arrangement of the device, thereby improving the power conversion efficiency of the solar device, and the stability of the device is also significantly improved, which promotes the large-scale and commercialization process of the perovskite solar cell.

[0038] In the preparation method of the present application, tris(2,2,2-trifluoroethyl) phosphate is introduced into the anti-solvent for preparing the perovskite film to regulate the crystallization of the perovskite film, so as to obtain high-quality light-absorbing materials and high-performance trans perovskite cells, wherein tris(2,2,2-trifluoroethyl) phosphate interacts with the perovskite film through three action sites: 1) the P=O bond in tris(2,2,2-trifluoroethyl) phosphate, which is equivalent to the action of a Lewis base, can passivate uncoordinated Pb2+ in the perovskite, which can form a coordination bond with the Pb 2+ ) ion, effectively passivating positive charge defects; 2) CF3 in tris(2,2,2-trifluoroethyl) phosphate can interact with FA+ / MA+ groups in the perovskite to form hydrogen bonds; 3) the C-O bond in tris(2,2,2-trifluoroethyl) phosphate also tightly binds to uncoordinated Pb2+ / Pb0, thereby passivating defects and regulating perovskite crystallization. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 TOF-SIMS characterization diagram of the perovskite active layer prepared for Example 2 and Comparative Example 2;

[0040] Figure 2 Steady-state photoluminescence spectrum and time-resolved fluorescence spectrum (a) is the steady-state photoluminescence spectrum, and (b) is the time-resolved fluorescence spectrum) of the perovskite active layer prepared for Example 2 and Comparative Example 2;

[0041] Figure 3 Dark-state J-V curve of the solar cell prepared for Example 2 and Comparative Example 2;

[0042] Figure 4 Space charge limited current (SCLC) diagram of the pure electronic device based on Example 2 and Comparative Example 2;

[0043] Figure 5 J-V diagram of the solar cell prepared for Example 2 and Comparative Example 2;

[0044] Figure 6Efficiency statistical distribution chart of Example 2, Example 4, Comparative Example 1, Comparative Example 2. DETAILED DESCRIPTION

[0045] In order for those skilled in the art to better understand the technical solutions of the application, the application will be further described in detail below with reference to the specific embodiments.

[0046] Example 1

[0047] The present embodiment provides a preparation method of a trans-perovskite solar cell, and the steps are as follows:

[0048] (1) Pretreatment of the substrate glass: the conductive glass ITO was sequentially treated with detergent, deionized water, isopropanol, acetone, and anhydrous ethanol for 20 min, and then dried with nitrogen. After ozone treatment for 25 min, it was taken into a nitrogen atmosphere glove box for standby.

[0049] (2) Deposition of the hole transport layer on the substrate glass: the hole transport layer material MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl] phosphonic acid) was dissolved in an ethanol solution (MeO-2PACz concentration of 0.5 mg / mL), and then 60-70 ul was taken for spin coating on the conductive glass treated with spin coating at a speed of 3000 rpm for 30 s. After spin coating, annealing was performed at a temperature of 100°C for 15 min to obtain the hole transport layer.

[0050] (3) Deposition of the perovskite active layer on the hole transport layer:

[0051] The perovskite light absorbing layer materials cesium iodide CsI (19.5 mg), rubidium iodide RbI (15.9 mg), methyl bromide amine MABr (8.4 mg), formamidine hydroiodide FAI (219.5 mg), lead iodide PbI2 (656.9 mg), and bromide iodide PbBr2 (27.5 mg) were dissolved in a DMF and DMSO (volume ratio of 4:1) mixture, and after shaking for 60 min, a perovskite precursor solution was obtained. Tris(2,2,2-trifluoroethyl) phosphate was dissolved in anisole to obtain a reverse solvent solution of tris(2,2,2-trifluoroethyl) phosphate with a concentration of 15 μL / ml;

[0052] A 100 ul perovskite precursor solution is spin-coated on the prepared hole transport layer in two steps, with the operating parameters set as 1000 rad / min for the first step, 500 rad / min for the acceleration, 10 s for the spin-coating time, and 4500 rad / min for the second step, 3000 rad / min for the acceleration, 40 s for the spin-coating time, and the anti-solvent solution 150 ul is added dropwise at the 45th second of the total time for extraction, with an extraction time of 2 s. The perovskite active layer is obtained after annealing at 150°C for 30 min after the perovskite precursor solution is spin-coated.

[0053] (4) Depositing an electron transport layer on the perovskite active layer: the electron transport layer material PCBM is dissolved in chlorobenzene (concentration of 30 mg / ml), and 80 ul is spin-coated on the surface of the perovskite active layer at a speed of 3000 rpm for 30 s. After spin-coating, annealing is performed at a temperature of 100°C for 10 min to obtain the electron transport layer.

[0054] (5) Depositing a metal electrode Ag on the electron transport layer: a metal electrode with a thickness of 100 nm is evaporated on the prepared electron transport layer by thermal evaporation under high vacuum.

[0055] Example 2

[0056] The same as Example 1, except that the concentration of tris(2,2,2-trifluoroethyl) phosphate in step (3) is 18 μL / ml.

[0057] Example 3

[0058] The same as Example 1, except that the concentration of tris(2,2,2-trifluoroethyl) phosphate in step (3) is 20 μL / ml.

[0059] Example 4

[0060] The same as Example 1, except that the concentration of tris(2,2,2-trifluoroethyl) phosphate in step (3) is 10 μL / ml.

[0061] Example 5

[0062] The same as Example 1, except that the dropwise addition process of the perovskite precursor solution and the anti-solvent in step (3) is as follows:

[0063] The perovskite precursor is spin-coated, and the spin coater is started when the precursor solution covers the ITO glass, spin-coated for 50 s, and the anti-solvent is added dropwise at the 45th second, and the anti-solvent is added dropwise within 2 s and placed on a 150°C hot stage for annealing within 30 s after spin-coating is completed.

[0064] Comparative Example 1

[0065] The same as example 1, except that the concentration of tris(2,2,2-trifluoroethyl) phosphate in step (3) is 30 μL / ml.

[0066] Comparative example 2

[0067] The same as example 2, except that no dropwise addition of the anisole solution dissolving tris(2,2,2-trifluoroethyl) phosphate is performed in step (3).

[0068] Effect example 1 TOF-SIMS characterization

[0069] The spatial distribution of key components in perovskite solar cells is detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS), see Figure 1 , wherein (a) corresponds to the depth profile and the corresponding three-dimensional distribution of the perovskite active layer prepared in comparative example 2, and (b) corresponds to the depth profile and the corresponding three-dimensional distribution of the perovskite active layer prepared in example 2.

[0070] From Figure 1 It can be seen that the characteristic elements I2 - are present in the entire bulk phase and the intensity does not change. The characteristic element F - of tris(2,2,2-trifluoroethyl) phosphate is only observed in the perovskite active layer of example 2, and F - signals along the perovskite grain boundary region can be observed, which are very low, but F - signals close to the bottom surface of the perovskite active layer increase sharply, which indicates that during the crystallization process from top to bottom, macromolecular tris(2,2,2-trifluoroethyl) phosphate is excluded at the perovskite grain boundary, and most of the tris(2,2,2-trifluoroethyl) phosphate molecules sink to the ITO substrate and adhere to the ITO / perovskite interface. At the same time, a small amount of tris(2,2,2-trifluoroethyl) phosphate remains on the upper surface of the perovskite before successfully migrating downward, which is consistent with the results of the three-dimensional distribution. The above shows that after the introduction of tris(2,2,2-trifluoroethyl) phosphate-containing antisolvent in the present application, the molecules are dispersed on the surface of the perovskite and inside the perovskite, which can regulate the crystallization of the perovskite.

[0071] Effect example 2 steady-state photoluminescence spectrum and time-resolved fluorescence spectrum characterization

[0072] The solar cells prepared in example 2 and comparative example 2 are characterized by steady-state photoluminescence (PL) and time-resolved fluorescence (TRPL) spectra to evaluate the effect of tris(2,2,2-trifluoroethyl) phosphate on the defect density and carrier performance of the perovskite film, see Figure 2Wherein (a) is a steady-state photoluminescence spectrum, (b) is a time-resolved fluorescence spectrum.

[0073] By Figure 2 It can be seen that when the sample is prepared on a glass substrate, the PL intensity of the perovskite active layer of Example 2 is about 2.1 times that of Comparative Example 2, indicating that Example 2 has better absorbance. The TRPL curve is analyzed by fitting the PL transient decay curve with an exponential function, and the parameter values are shown in Table 1. It can be seen that the average carrier lifetime (τa) of Comparative Example 2 is 320.22 ns, and the average carrier lifetime (τa) of Example 2 is 481.78 ns. The average carrier lifetime of the perovskite active layer of the solar cell of the present application is significantly improved, indicating that the treatment of tris(2,2,2-trifluoroethyl) phosphate reduces non-radiative recombination, which is a prerequisite for high-quality polycrystalline thin films, and leads to high V oc . It indicates that tris(2,2,2-trifluoroethyl) phosphate improves the transport of carriers and suppresses non-radiative recombination.

[0074] Table 1. Time-resolved fluorescence spectrum parameters of Comparative Example 2 and Example 2

[0075]

[0076] Effect Example 3: Electrochemical performance test

[0077] Figure 3 The dark-state J-V curve of the solar cell prepared for Example 2 and Comparative Example 2 can be seen. The reverse leakage current density of Comparative Example 2 is 2.17 x 10 -2 mA / cm 2 ; the reverse leakage current density of the solar cell of Example 2 is 2.78 x 10 - 3 mA / cm 2 , which is significantly reduced compared with Comparative Example 2, meaning that non-radiative recombination is significantly suppressed.

[0078] Figure 4 The space charge limited current (SCLC) based on pure electron devices for Example 2 and Comparative Example 2. According to the trap filling limit voltage (V TFL ) at the inflection point, the trap density can be obtained according to the formula:

[0079] N t =2εε0V TEL / (eL 2 );

[0080] Where N t is the trap density, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, e is the elementary charge, and L is the thickness of the perovskite thin film (700 nm).

[0081] Figure 4 It can be seen that the V TFL of Comparative Example 2 is 0.30 V, while the V TFL of Example 2 is reduced to 0.22 V, indicating that the trap density of Example 2 is significantly reduced. The reduction of defect density can be due to the P=O, CF3, C-O and other functional groups contained in the tris(2,2,2-trifluoroethyl) phosphate molecule, indicating that these functional groups have a certain defect passivation effect on the perovskite film, and are beneficial to the extraction and transmission of charges.

[0082] Figure 5 The J-V diagram of the solar cell prepared in Example 2 and Comparative Example 2 is shown in Table 2. The specific photovoltaic parameters are shown in Table 2.

[0083] Table 2. J-V parameters of reference device and target device

[0084]

[0085] It can be seen that the PCE of the solar cell prepared in Comparative Example 2 is 23.15%, the Voc is 1.13 V, the Jsc is 25.17 mA cm -2 , and the FF is 81.21%. The solar cell prepared in Example 2 shows a PCE of 24.91%, while the Voc is 1.16 V, the Jsc is 25.45 mA cm -2 , and the FF is 84.20%, indicating that the solar cell prepared by the method of the present application has better electrochemical performance.

[0086] The present application selects 30 effective electrodes of the solar cells prepared in Example 2, Example 4 and Comparative Examples 1-2 to make efficiency statistical distribution diagram, see Figure 6 It can be clearly seen that the solar cells prepared in Example 2 and Example 4 of the present application have higher efficiency and better repeatability. The comparison of Comparative Example 1 and Comparative Example 2 shows that if the concentration of tris(2,2,2-trifluoroethyl) phosphate molecules added in the present application is excessive, the electrochemical performance will be worse, so it is necessary to strictly control the amount of tris(2,2,2-trifluoroethyl) phosphate molecules.

[0087] The above is only a preferred embodiment of the present application, and it should be pointed out that the above preferred embodiment should not be regarded as a limitation of the present application, and the protection scope of the present application should be limited by the scope defined in the claims. For ordinary skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A reverse perovskite solar cell, characterized in that, The structure of the inverted perovskite solar cell, from top to bottom, includes: a metal electrode, an electron transport layer, a perovskite active layer, a hole transport layer, and a substrate glass. The perovskite active layer contains tris(2,2,2-trifluoroethyl) phosphate.

2. The inverted perovskite solar cell according to claim 1, characterized in that, The metal electrode material is selected from any one of gold, silver, copper, and aluminum.

3. The inverted perovskite solar cell according to claim 1, characterized in that, The electron transport layer material is selected from any one or more of PCBM and BCP.

4. The inverted perovskite solar cell according to claim 1, characterized in that, The perovskite active layer material is selected from one or more of organic amine salts and lead halide salts.

5. The inverted perovskite solar cell according to claim 1, characterized in that, The hole transport layer material is MeO-2PACz.

6. A method for fabricating an inverted perovskite solar cell, characterized in that, Includes the following steps: S1. Clean the substrate glass; S2. Deposit a hole transport layer on the substrate glass; S3. Deposit a perovskite active layer on the hole transport layer: Prepare a perovskite precursor solution and an antisolvent containing tris(2,2,2-trifluoroethyl) phosphate. Spin-coat the perovskite precursor solution onto the hole transport layer. In the last 5 seconds before spin-coating is complete, start adding and add the antisolvent dropwise. Then anneal the solution to obtain the perovskite active layer. S4. Deposit an electron transport layer on the perovskite active layer; S5. Deposit a metal electrode on the electron transport layer.

7. The preparation method according to claim 6, characterized in that, In step S3, the precursor solution is prepared by dissolving the perovskite active layer material in a solvent, wherein the solvent is DMF and DMSO in a volume ratio of 4:

1.

8. The preparation method according to claim 6, characterized in that, The antisolvent in S3 is prepared by dissolving tris(2,2,2-trifluoroethyl) phosphate in anisole.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The concentration of tris(2,2,2-trifluoroethyl) phosphate in the antisolvent of S3 is 10-20 μL / ml.

10. The preparation method according to any one of claims 6 to 8, characterized in that, In step S3, the spin-coating process of the perovskite precursor solution and the dropwise addition of the antisolvent are as follows: the perovskite precursor solution is spin-coated on the hole transport layer in two steps. The spin-coating parameters for the two steps are 1000 rad / min rotation speed, 500 rad / min acceleration, and 10 s spin-coating time, and 4500 rad / min rotation speed, 3000 rad / min acceleration, and 40 s spin-coating time, respectively. At the 45th second of the total time, the antisolvent solution is added dropwise for extraction, and the extraction time is 2 seconds.

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