Perovskite precursor solution, perovskite solar cell and preparation method thereof

Abstract

The invention relates to the technical field of perovskite solar cells, in particular to a perovskite precursor solution, a perovskite solar cell and a preparation method of the perovskite solar cell. The perovskite precursor solution contains an additive; the additive is selected from any one or more of 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylpyrimidine thiocyanate, 1-butyl-3-methylpyrimidine thiocyanate and 1-butyl-3-methylimidazolium thiocyanate, and the additive is selected from any one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylpyrimidine thiocyanate, 1-butyl-3-methylpyrimidine thiocyanate and 1-butyl-3-methylimidazolium hexafluorophosphate. By adding the additive into the perovskite precursor solution, a perovskite thin film with more uniform crystal grains, fewer defects and stronger light absorption capability is obtained, so that the open-circuit voltage (VOC) and short-circuit current density (JSC) of the wide-band-gap perovskite solar cell are improved, and the photoelectric conversion efficiency of the cell is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a perovskite precursor solution, a perovskite solar cell and a preparation method thereof. Background Art

[0002] Perovskite materials have attracted extensive attention from researchers due to their excellent performance of high absorption coefficient and wide adjustable band gap. However, the phase separation caused by the high Br content (≥50%) in the top wide band gap perovskite material and the severe non-radiative recombination caused by ion migration have caused serious damage to the conversion efficiency and stability of solar cells. In addition, due to its rapid and uncontrollable crystallization, additional halogen vacancies (such as iodine vacancies and bromine vacancies) may be generated in the lattice of high bromine content wide band gap perovskites, and the halide phase segregation caused by halogen vacancies assisted ion migration in wide band gap perovskites greatly limits the efficiency and life of solar cells. Therefore, it is necessary to suppress the halide phase segregation in these perovskites by blocking the migration path of halide ions at grain boundaries and in the lattice.

[0003] The existing technology uses lead thiocyanate, rubidium thiocyanate or formamidinium thiocyanate as perovskite precursor additives. Although it can effectively improve the open circuit voltage of wide-bandgap perovskite solar cells, the short-circuit current of the solar cell cannot be improved, which results in the overall efficiency cannot be further improved. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a perovskite precursor solution, a perovskite solar cell and a preparation method thereof. The present invention adds the additive to the perovskite precursor solution to obtain a perovskite film with more uniform grains, fewer defects and stronger light absorption capacity, thereby improving the open circuit voltage (VOC) and short circuit current density (JSC) of the wide bandgap perovskite solar cell, thereby improving the photoelectric conversion efficiency of the cell.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a perovskite precursor solution, which contains an additive, and the additive is selected from any one or more of 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylpyrimidine thiocyanate, 1-butyl-3-methylpyrimidine thiocyanate, and 1-butyl-3-methylimidazolium thiocyanate.

[0007] Preferably, the mass volume ratio of the additive to the perovskite precursor solution is 0.5-4 mg / mL.

[0008] In some embodiments of the present invention, the mass volume ratio of the additive to the perovskite precursor solution is any one of 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL or a value between two of them.

[0009] In a second aspect, the present invention provides a perovskite solar cell, the structure of which includes a perovskite light-absorbing layer, and the perovskite light-absorbing layer is prepared from the above-mentioned perovskite precursor solution.

[0010] Preferably, the structure of the perovskite solar cell further includes conductive glass, an electron transport layer, a perovskite light absorption layer, a hole transport layer, and a metal electrode.

[0011] Preferably, the material of the electron transport layer is selected from fullerene derivatives (such as PCBM) or C60.

[0012] Preferably, the raw material of the perovskite light-absorbing layer is selected from one or more of cesium iodide (CsI), lead iodide (PbI), lead bromide (PbBr2), formamidine hydroiodide (FAI), lead chloride (PbCl2), and methylammonium chloride (MACl).

[0013] Preferably, the material of the hole transport layer is selected from one or more of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphoric acid (Me-4PACz), [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid (4PADCB), and (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid (MeO-2PACz).

[0014] Preferably, the metal electrode is selected from any one of Ag, Au or Cu.

[0015] In a third aspect, the present invention provides a method for preparing a perovskite solar cell, comprising the following steps:

[0016] Clean the conductive glass, prepare a hole transport layer, prepare a perovskite light absorbing layer, prepare an electron transport layer, and prepare a metal electrode, wherein the perovskite light absorbing layer is prepared from the perovskite precursor solution.

[0017] Preferably, the process of preparing the perovskite light-absorbing layer is: spin-coating the perovskite precursor solution on a substrate, and then dripping an anti-solvent and annealing to obtain the perovskite light-absorbing layer.

[0018] Preferably, the spin coating process is a two-step spin coating process, wherein the first step spin coating parameters are a rotation speed of 1000 rpm, an acceleration of 500 rpm / s, and a spin coating time of 10 seconds, and the second step spin coating parameters are a rotation speed of 5000 rpm, an acceleration of 3000 rpm / s, and a spin coating time of 40 seconds.

[0019] Preferably, the annealing parameters are a temperature of 100° C. and an annealing time of 10 minutes.

[0020] The beneficial effects of the present invention are:

[0021] The present invention adds an additive to a perovskite precursor solution, and the additive is selected from any one or more of 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylpyrimidine thiocyanate, 1-butyl-3-methylpyrimidine thiocyanate, and 1-butyl-3-methylimidazolium thiocyanate. A perovskite film with more uniform grains, fewer defects, and stronger light absorption capacity is obtained, thereby improving the open circuit voltage (VOC) and short circuit current density (JSC) of a wide bandgap perovskite solar cell, thereby improving the photoelectric conversion efficiency of the cell. Taking 1-ethyl-3-methylimidazolium thiocyanate as an example, it contains 1-ethyl-3-methylimidazolium cation and thiocyanate anion, which has two advantages. On the one hand, one molecule realizes two stable lattice structure mechanisms: one is that the radius of thiocyanate anion is similar to that of iodine atom, so it can replace iodine atom to enter the lattice, thereby reducing the large number of iodine atom vacancies generated after the device is exposed to light; the other is that the lone pair of electrons of nitrogen atom in 1-ethyl-3-methylimidazolium cation can form coordination bond with lead atom in perovskite, and coordination bond is a kind of covalent bond, so this combination mode can further stabilize the lattice structure. On the other hand, compared with thiocyanate molecules with single functional groups, such as formamidine thiocyanate, rubidium thiocyanate, etc., the molecule of the present invention realizes V OC With J SC The additive of the present invention not only improves the short-circuit current of the device, but also the thiocyanate anion improves the open-circuit voltage of the device, thereby further improving the overall performance and stability of the device over the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The JV curves of the perovskite solar cells prepared in each embodiment and comparative example 1 are shown;

[0023] Figure 2 The JV curve diagram (a) and the short-circuit current box diagram (b) of the perovskite solar cells prepared in Example 2 and Comparative Example 1 and Comparative Example 2;

[0024] Figure 3 XRD spectra (a) and (100) half-peak width ratio diagram (b) of the perovskite light absorbing layers prepared in Example 2 and Comparative Example 1;

[0025] Figure 4 SEM images of the perovskite light-absorbing layers prepared in Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0027] Example 1

[0028] The present embodiment provides a perovskite precursor solution: 0.0433 g of cesium iodide, 0.0516 g of lead iodide, 0.3037 g of lead bromide, 0.1224 g of formamidine hydroiodide, 0.0107 g of lead chloride, 0.004 g of methylammonium chloride and 1-ethyl-3-methylimidazole thiocyanate (EImSCN) are weighed and mixed, 1 mL of a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is added to the mixed solution (the volume ratio of DMF:DMSO is 4:1), and the solution is placed on a stirrer until it is completely dissolved, wherein the amount of 1-ethyl-3-methylimidazole thiocyanate (EImSCN) added is 0.5 mg / mL.

[0029] This embodiment provides a perovskite solar cell, whose structure includes conductive glass, an electron transport layer, a perovskite light absorbing layer (prepared from the above-mentioned perovskite precursor solution), a hole transport layer, and a metal electrode.

[0030] This embodiment provides a method for preparing a perovskite solar cell, the steps are as follows:

[0031] (1) Cleaning conductive glass: The indium tin oxide (ITO) substrate is treated in a UV ozone cleaning machine for 15 minutes to clean impurities on the substrate surface and improve wettability;

[0032] (2) Preparation of hole transport layer: 65 μL of 0.5 mg / ml ME-4PACZ solution (solvent: ethanol) was spin-coated on a conductive glass substrate at a speed of 4000 rpm for 30 s and an acceleration of 4000 rpm / s, followed by annealing at 100°C for 10 min;

[0033] (3) Preparation of perovskite light absorbing layer: 0.05 mL of the pre-prepared perovskite precursor solution was dripped onto the hole transport layer, and then the perovskite was spin-coated using a two-step spin coating method. The first step spin coating parameters were a rotation speed of 1000 rpm, an acceleration of 500 rpm / s, and a spin coating time of 10 seconds. The second step spin coating parameters were a rotation speed of 5000 rpm, an acceleration of 3000 rpm / s, and a spin coating time of 40 seconds. At the 15th second before the end of the spin coating, 175 μL of anisole anti-solvent was dripped. After the spin coating was completed, the layer was annealed at 100° C. for 10 minutes.

[0034] (4) Preparation of electron transport layer: Spin-coat 70 μL of 20 mg / ml PCBM solution (the solvent is chlorobenzene) on the perovskite light absorbing layer at a spin-coating speed of 1500 rpm for 30 s at an acceleration of 1500 rpm / s;

[0035] (5) Preparation of metal electrodes: Use an aperture area of ​​0.0900 cm 2 The mask is placed on the top layer of the glass, and then Ag with a thickness of 120nm is evaporated as a metal electrode.

[0036] Example 2

[0037] Same as Example 1, except that the added amount of 1-ethyl-3-methylimidazole thiocyanate is 1 mg / mL.

[0038] Example 3

[0039] Same as Example 1, except that the added amount of 1-ethyl-3-methylimidazole thiocyanate is 2 mg / mL.

[0040] Example 4

[0041] Same as Example 1, except that the added amount of 1-ethyl-3-methylimidazole thiocyanate is 3 mg / mL.

[0042] Example 5

[0043] Same as Example 1, except that the added amount of 1-ethyl-3-methylimidazole thiocyanate is 4 mg / mL.

[0044] Example 6

[0045] The same as Example 2, except that 1-ethyl-3-methylimidazolium thiocyanate in the perovskite precursor solution is replaced by 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0046] Example 7

[0047] The same as Example 2, except that 1-ethyl-3-methylimidazolium thiocyanate in the perovskite precursor solution is replaced by 1-ethyl-3-methylimidazolium hexafluorophosphate.

[0048] Example 8

[0049] Same as Example 2, except that 1-ethyl-3-methylimidazole thiocyanate in the perovskite precursor solution is replaced by 1-ethyl-3-methylpyrimidine thiocyanate.

[0050] Example 9

[0051] The same as Example 2, except that 1-ethyl-3-methylimidazole thiocyanate in the perovskite precursor solution is replaced by 1-butyl-3-methylpyrimidine thiocyanate.

[0052] Example 10

[0053] The same as Example 2, except that 1-ethyl-3-methylimidazole thiocyanate in the perovskite precursor solution is replaced by 1-butyl-3-methylimidazole thiocyanate.

[0054] Comparative Example 1

[0055] The same as Example 1, except that 1-ethyl-3-methylimidazole thiocyanate is not added to the perovskite precursor solution.

[0056] Comparative Example 2

[0057] The same as Example 1, except that 1-ethyl-3-methylimidazole thiocyanate in the perovskite precursor solution is replaced by formamidine thiocyanate (FASCN), and the added amount is 1.5 mg / ml.

[0058] Effect Example 1 Electrochemical Performance Test

[0059] The electrochemical performance of the perovskite solar cells prepared in the examples and comparative examples was tested. The results are shown in Table 1. Figure 1-2 .

[0060] Table 1

[0061]

[0062] From Table 1 and Figure 1 It can be seen that compared with Comparative Example 1, the electrochemical performance of the perovskite solar cells prepared by adding 1-ethyl-3-methylimidazole thiocyanate to the perovskite precursor solution of Example 1 is improved. Among them, when the concentration of 1-ethyl-3-methylimidazole thiocyanate in Example 2 is 1 mg / ml, the solar cell efficiency reaches 16.14%, and the improvement effect is most significant.

[0063] In addition, the prior art uses lead thiocyanate, rubidium thiocyanate or formamidinium thiocyanate as additives to the perovskite precursor solution to increase the open circuit voltage of wide bandgap perovskite solar cells, but it cannot increase the short circuit current and overall efficiency of the battery. Figure 2As shown, the present invention tests the JV curve and the short-circuit current box diagram of the perovskite solar cell prepared in Example 2 and Comparative Example 2. It can be seen that compared with Comparative Example 2, the present invention can effectively improve the short-circuit current of the perovskite battery. This is mainly because the 1-ethyl-3-methylimidazolium cation and the thiocyanate anion in 1-ethyl-3-methylimidazolium thiocyanate carry out two lattice stabilization mechanisms. On the one hand, the thiocyanate anion radius is similar to that of the iodine atom, which can replace the iodine atom to enter the lattice, thereby reducing the generation of a large number of iodine atom vacancies after the device is exposed to light; on the other hand, the lone pair of electrons of the nitrogen atom in the 1-ethyl-3-methylimidazolium cation can form a coordination bond with the lead atom in the perovskite, and the coordination bond belongs to a kind of covalent bond. Such a combination mode can further stabilize the lattice structure, improve the short-circuit current of the device, and then improve the overall performance and stability of the device.

[0064] Effect Example 2 XRD Characterization

[0065] Figure 3 The XRD diagram and the half-peak width of the (100) crystal plane of the perovskite light-absorbing layer prepared in Example 2 and Comparative Example 1 are compared. It can be seen that compared with Comparative Example 1, the 1-ethyl-3-methylimidazolium thiocyanate molecule contained in Example 2 enhances the crystallinity of the perovskite film, and the molecule slows down the crystallization rate and improves the overall crystallinity of the film, indicating that the lone pair of electrons of the nitrogen atom in the 1-ethyl-3-methylimidazolium cation can form a coordination bond with the lead atom in the perovskite, which can further stabilize the lattice structure.

[0066] Effect Example 3 Surface morphology characterization

[0067] Figure 4 The SEM images of the perovskite light-absorbing layers prepared in Example 2 and Comparative Example 1. Under a field emission scanning electron microscope with a resolution of 50,000 times, it can be seen that the addition of 1-ethyl-3-methylimidazole thiocyanate molecules inhibits the precipitation of lead iodide and makes the grains more uniform, which is consistent with the XRD test results.

[0068] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A perovskite precursor solution, characterized in that: The perovskite precursor solution contains an additive, and the additive is selected from any one or more of 1-ethyl-3-methylimidazole thiocyanate, 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole hexafluorophosphate, 1-ethyl-3-methylpyrimidine thiocyanate, 1-butyl-3-methylpyrimidine thiocyanate, and 1-butyl-3-methylimidazole thiocyanate.

2. The perovskite precursor solution according to claim 1, characterized in that The mass volume ratio of the additive to the perovskite precursor solution is 0.5-4 mg / mL.

3. A perovskite solar cell, characterized in that: The structure of the perovskite solar cell includes a perovskite light-absorbing layer, and the perovskite light-absorbing layer is prepared from the perovskite precursor solution according to claim 1 or 2.

4. The perovskite solar cell according to claim 3, characterized in that: The structure of the perovskite solar cell also includes conductive glass, an electron transport layer, a perovskite light absorption layer, a hole transport layer, and a metal electrode.

5. The perovskite solar cell according to claim 4, characterized in that: The material of the electron transport layer is selected from fullerene derivatives or C60.

6. The perovskite solar cell according to any one of claims 3 to 5, characterized in that: The raw material of the material of the perovskite light-absorbing layer is selected from one or more of cesium iodide, lead iodide, lead bromide, formamidine hydroiodide, lead chloride, and methylammonium chloride.

7. A method for preparing a perovskite solar cell, characterized in that: The following steps are involved: Cleaning conductive glass, preparing a hole transport layer, preparing a perovskite light absorbing layer, preparing an electron transport layer, and preparing a metal electrode, wherein the perovskite light absorbing layer is prepared from the perovskite precursor solution according to claim 1 or 2.

8. The preparation method according to claim 7, characterized in that: The process of preparing the perovskite light-absorbing layer is: spin-coating the perovskite precursor solution on a substrate, then dripping an anti-solvent and annealing to obtain the perovskite light-absorbing layer.

9. The preparation method according to claim 8, characterized in that: The spin coating is a two-step spin coating, wherein the first step spin coating parameters are a rotation speed of 1000 rpm, an acceleration of 500 rpm / s, and a spin coating time of 10 seconds, and the second step spin coating parameters are a rotation speed of 5000 rpm, an acceleration of 3000 rpm / s, and a spin coating time of 40 seconds.

10. The preparation method according to claim 8, characterized in that: The annealing parameters are a temperature of 100° C. and an annealing time of 10 minutes.

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