A carbon quantum dot and a preparation method, application, perovskite precursor liquid and a preparation method thereof, and a perovskite solar cell and a preparation method thereof

Abstract

The application provides a carbon quantum dot and a preparation method and application thereof, a perovskite precursor solution and a preparation method thereof, and a perovskite solar cell and a preparation method thereof, and comprises the following steps: dissolving melamine in a solvent, and then heating and reacting in a reaction kettle to obtain the carbon quantum dot. The carbon quantum dot provided by the application not only has low preparation cost, but also can effectively improve the morphology characteristics of a perovskite layer in the preparation process of the perovskite layer, so that the surface of the final perovskite layer is smoother, the agglomeration of crystal grains is reduced, and thus the defect sites are effectively reduced, and the film forming quality of the perovskite layer is improved. On this basis, the charge recombination in the perovskite solar cell is effectively reduced, the carrier extraction speed and transmission speed are significantly accelerated, and finally the photoelectric conversion efficiency of the battery is obviously improved. In addition, the carbon quantum dot of the application can also improve the stability of the perovskite layer, inhibit the decomposition of the perovskite layer, and thus effectively improve the service life of the perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cells, and in particular to a carbon quantum dot and its preparation method, its application, a perovskite precursor solution and its preparation method, and a perovskite solar cell and its preparation method. Background Technology

[0002] In recent years, perovskite solar cells have been widely studied due to their advantages such as high light absorption coefficient, long carrier diffusion length, and low fabrication cost. However, at present, the actual photoelectric conversion efficiency of perovskite solar cells is still significantly lower than their theoretical limit. One of the important factors limiting the improvement of photoelectric conversion efficiency is the presence of halogen vacancies and uncoordinated Pb. 2+ These factors lead to poor perovskite layer film quality in perovskite solar cells, with high defect density at grain boundaries, significantly exacerbating nonradiative recombination. Summary of the Invention

[0003] Therefore, it is necessary to address the problem that poor perovskite film quality limits the improvement of photoelectric conversion efficiency of perovskite solar cells by providing a method for preparing carbon quantum dots, their applications, perovskite precursor solutions and their preparation methods, and perovskite solar cells and their preparation methods.

[0004] The technical solution provided by this invention is as follows:

[0005] A method for preparing carbon quantum dots includes: dissolving melamine in a solvent, and then heating and reacting it in a reaction vessel to obtain the carbon quantum dots.

[0006] In some embodiments of this application, the solvent is methanol, the reaction temperature in the reactor is 180°C, and the reaction time is 36 hours.

[0007] A carbon quantum dot is prepared using the aforementioned method for preparing carbon quantum dots.

[0008] The application of carbon quantum dots in improving the quality of perovskite film formation.

[0009] The application of the carbon quantum dots in the fabrication of perovskite solar cells.

[0010] A perovskite precursor liquid comprising MAPbI3 and the aforementioned carbon quantum dots.

[0011] A method for preparing a perovskite precursor solution, comprising:

[0012] Weigh MAI and PbI2 in a molar ratio of 1:1 and dissolve them in a mixture of DMF and DMSO to form a first solution;

[0013] The carbon quantum dots are dissolved in a mixture of DMF and DMSO to form a second solution;

[0014] The first solution and the second solution are mixed to form the perovskite precursor solution.

[0015] In some embodiments of this application, the concentration of MAPbI3 in the first solution is 1 mmol / mL, the concentration of carbon quantum dots in the second solution is 25 mg / mL, and the concentration of carbon quantum dots in the perovskite precursor solution is 4 mg / mL.

[0016] A perovskite solar cell includes a conductive glass layer, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer arranged sequentially in layers, wherein the perovskite layer is obtained by spin-coating the perovskite precursor solution.

[0017] A method for fabricating a perovskite solar cell, comprising:

[0018] NiCl2 and NaOH are mixed to obtain NiO. x Nanoparticles, then NiO x Nanoparticles dissolve in deionized water to form NiO x Solution;

[0019] NiO x The solution is spin-coated onto a conductive glass layer to form a hole transport layer;

[0020] The perovskite precursor liquid is spin-coated onto the hole transport layer to form a perovskite layer.

[0021] PC 61 BM's chlorobenzene solution is spin-coated onto the perovskite layer to form an electron transport layer;

[0022] Silver is deposited on the electron transport layer to form an electrode layer.

[0023] The beneficial effects of this invention are as follows:

[0024] The carbon quantum dots provided by this invention are not only inexpensive to prepare, but also effectively improve the morphology of the perovskite layer during the preparation process, resulting in a smoother surface and reduced grain agglomeration, thereby effectively reducing defect sites and improving the film quality of the perovskite layer.

[0025] Based on this, charge recombination in perovskite solar cells is effectively reduced, and the carrier extraction and transport rates are significantly accelerated, ultimately resulting in a significant improvement in the photoelectric conversion efficiency of the cell. Furthermore, the carbon quantum dots of this invention can also enhance the stability of the perovskite layer and inhibit its decomposition, thereby effectively extending the lifespan of the perovskite solar cell. Attached Figure Description

[0026] Figure 1 This is a TEM image of the carbon quantum dots in Example 4 of the present invention;

[0027] Figure 2 The Raman spectrum of the carbon quantum dots in Example 4 of this invention;

[0028] Figure 3 The N 1s high-resolution XPS spectrum of the carbon quantum dots in Example 4 of this invention;

[0029] Figure 4 The UV-Vis absorption spectrum, PL spectrum, and PLE spectrum of carbon quantum dots in Example 4 of this invention;

[0030] Figure 5 The images shown are SEM images of the perovskite layers in the comparative examples and Example 4 of this invention.

[0031] Figure 6 The image shows the XRD pattern of the perovskite layer in the comparative example of this invention.

[0032] Figure 7 The image shown is the XRD pattern of the perovskite layer in Example 4 of this invention.

[0033] Figure 8 EDS images of the perovskite layers in the comparative examples and Example 4 of this invention;

[0034] Figure 9 This is a C-AFM current mapping diagram of the perovskite layer in the comparative example and Example 4 of the present invention;

[0035] Figure 10 The Mott-Schottky curves of the perovskite solar cells in the comparative examples and Example 4 of this invention are shown.

[0036] Figure 11 The EQE spectrum and integrated current curve of the perovskite solar cells in the comparative example and Example 4 of this invention;

[0037] Figure 12 The TPV decay curves of the perovskite solar cells in the comparative examples and Example 4 of this invention are shown.

[0038] Figure 13 The TPC decay curves of the perovskite solar cells in the comparative examples and Example 4 of this invention are shown.

[0039] Figure 14 The carrier transport characteristic curves of the perovskite solar cells in the comparative examples and Example 4 of this invention are shown.

[0040] Figure 15 The dark-state current-voltage (IV) characteristic curves of the perovskite solar cells in the comparative examples and Example 4 of this invention are shown.

[0041] Figure 16 The graphs show the efficiency and stability test results of the perovskite solar cells in the comparative example and Example 4 of this invention. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0043] Example 1:

[0044] This embodiment provides a carbon quantum dot, the preparation method of which includes the following steps: 252 mg of melamine is weighed and added to 15 mL of methanol. The mixture is magnetically stirred to fully disperse it and form a uniform solution. Then, it is heated to 180°C in a reaction vessel and reacted for 36 h. After the reaction is completed, it is cooled to room temperature. The liquid obtained from the reaction is filtered using filter paper with a pore diameter of 0.22 μm. The filtrate is transferred to a rotary evaporator to remove the solvent. Deionized water is added to the product after rotary evaporation. Finally, the mixture is dialyzed with a 1000 Da dialysis membrane for 24 h. During the dialysis process, the ultrapure water is replaced every 12 h. Finally, the mixture is freeze-dried to obtain the carbon quantum dots.

[0045] like Figure 1 As shown, the carbon quantum dots exhibit good dispersion with a lattice spacing of 2.079 Å, matching the (100) facet of graphite. Figure 2 As shown, the carbon quantum dots at 1380 cm⁻¹ -1 The D peak intensity at 1585 cm⁻¹ and at 1585 cm⁻¹ -1 The intensity ratio of the G peak at that location is 0.87, further demonstrating that the carbon quantum dots possess a high degree of crystallinity. Figure 3 As shown, a distinct peak corresponding to pyrrole N is observed at 399.6 eV, the appearance of which proves that melamine fully formed the carbon quantum dots through self-polymerization. Figure 4 As shown, the carbon quantum dot has two excitation wavelengths (395 nm and 460 nm) and one emission wavelength (555 nm).

[0046] This embodiment also provides a hole transport material, the preparation method of which includes the following steps: 12.885 g of NiCl2·6H2O is weighed and added to 100 mL of deionized water, and magnetically stirred until completely dissolved. During the stirring process, 10 mol / L NaOH solution is added dropwise until the pH of the solution rises to 10. During this process, a turbid light green precipitate gradually forms. The supernatant is then removed by centrifugation, the precipitate is washed twice with deionized water, and then dried at 80°C. The resulting dry powder is calcined at 270°C for 2 hours to obtain black NiO. x Nanoparticles (i.e., hole transport materials). NiO x Nanoparticles dispersed in deionized water form NiO x Solution, in which NiO x The concentration of the solution is 25 mg / mL.

[0047] This embodiment also provides a perovskite precursor solution, the preparation method of which includes the following steps:

[0048] Step 101: Weigh MAI and PbI2 at a molar ratio of 1:1 and add them to a mixture of DMF and DMSO (the volume ratio of DMF to DMSO is 7:3) to form a first solution with a MAPbI3 concentration of 1 mmol / mL.

[0049] Step 102: Disperse the carbon quantum dots in a mixture of DMF and DMSO (the volume ratio of DMF to DMSO is 7:3) to form a second solution with a carbon quantum dot concentration of 25 mg / mL.

[0050] Step 103: Mix the first solution and the second solution to form a perovskite precursor solution with a carbon quantum dot concentration of 1 mg / mL.

[0051] This embodiment also provides a perovskite solar cell, comprising a conductive glass layer, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer arranged sequentially in layers.

[0052] The fabrication method of the perovskite solar cell includes the following steps:

[0053] Step 201: Clean the FTO conductive glass (conductive glass layer) with deionized water and ethanol for 15 minutes in sequence, and then perform UV-ozone treatment for 15 minutes.

[0054] Step 202: The aforementioned NiO x The solution (25 mg / mL) was spin-coated onto FTO conductive glass at a spin speed of 2000 rpm for 30 s, and then annealed at 130 °C for 20 min to form a hole transport layer.

[0055] Step 203: In a nitrogen atmosphere within a glove box, spin-coat the perovskite precursor solution onto the hole transport layer at a spin-coating speed of 2800 rpm for 30 seconds. Chlorobenzene is added dropwise as an anti-solvent during the spin-coating process. After spin-coating, anneal the perovskite layer sequentially at four temperatures: 40℃, 60℃, 80℃, and 100℃ for 5 minutes each.

[0056] Step 204: Add 20 mg / mL PC 61 BM's chlorobenzene solution was spin-coated onto the perovskite layer at a speed of 2500 rpm for 30 seconds, and then heated at 60°C for 10 minutes to form the electron transport layer.

[0057] Step 205: An 80 nm thick Ag electrode (electrode layer) is deposited on the electron transport layer by vapor deposition.

[0058] Example 2:

[0059] The difference between this embodiment and Example 1 is that the concentration of carbon quantum dots in the perovskite precursor solution is 2 mg / mL.

[0060] Example 3:

[0061] The difference between this embodiment and Example 1 is that the concentration of carbon quantum dots in the perovskite precursor solution is 3 mg / mL.

[0062] Example 4:

[0063] The difference between this embodiment and Example 1 is that the concentration of carbon quantum dots in the perovskite precursor solution is 4 mg / mL.

[0064] Comparative example:

[0065] The difference between this comparative example and Example 1 is that the first solution was not mixed with the second solution; instead, the first solution was directly spin-coated onto the hole transport layer to obtain the perovskite layer. The spin-coating speed of the first solution was also 2800 rpm, and the spin-coating time was 30 s. Chlorobenzene was added dropwise as an anti-solvent during the spin-coating process.

[0066] like Figure 5 As shown, in the comparative example, the perovskite layer without carbon quantum dots is in a state of dispersed grains and uneven size, with fine bumps and pores on the surface. However, in Example 4, after the perovskite layer was doped with carbon quantum dots, the surface was smoother, the grain aggregation was reduced, and the overall morphology uniformity was significantly improved, which confirms that the carbon quantum dots can effectively improve the film quality of the perovskite layer.

[0067] like Figure 6 and Figure 7As shown, by doping with carbon quantum dots, the intensity of the diffraction peak corresponding to the (002) crystal plane of the perovskite layer increases, while a new diffraction peak corresponding to the (100) crystal plane appears in the perovskite layer, indicating that carbon quantum dots improve the crystallinity of the perovskite layer. Meanwhile, since the diffraction peak corresponding to the (002) crystal plane did not shift significantly before and after carbon quantum doping, it indicates that carbon quantum dots did not change the crystal structure of the perovskite, but only played a role in regulating the crystallization process.

[0068] like Figure 8 As shown, the perovskite layer without carbon quantum doping exhibits uneven lattice fringes, with lattice disorder and numerous lattice defects in localized areas. In contrast, the perovskite layer with carbon quantum doping shows more continuous and regular lattice fringes, with a significant reduction in defect sites. This indicates that carbon quantum dots can passivate lattice defects in perovskite and enhance the crystal's orderliness.

[0069] like Figure 9 As shown, the surface current distribution of the perovskite layer without carbon quantum doping is extremely uneven, with large fluctuations and generally low current values; while the surface current distribution of the perovskite layer doped with carbon quantum dots is more uniform, and the current values ​​are significantly increased, greatly improving the uniformity of material conductivity. This demonstrates the optimizing effect of carbon quantum doping on the surface electrical properties of the perovskite layer.

[0070] like Figure 10 As shown, the slope of the curve for the undoped perovskite layer is smaller, corresponding to a lower carrier concentration; while the slope of the curve for the doped perovskite layer is relatively larger, the carrier concentration is significantly increased, and the overall linearity of the curve is good. This indicates that carbon quantum doping has a better control over the space charge layer characteristics of perovskite and promotes the separation of photogenerated carriers.

[0071] The photoelectric data of the perovskite solar cells in the comparative examples and Examples 1-4 are shown in Table 1.

[0072] Table 1

[0073]

[0074] Based on Table 1, it can be clearly seen that at AM 1.5G (100 mW·cm⁻¹), -2 Under standard illumination conditions, as the carbon quantum dot doping content increases, the open-circuit voltage, short-circuit current density, and fill factor of perovskite solar cells all gradually increase, resulting in a significant increase in cell efficiency.

[0075] like Figure 11 As shown, by doping with carbon quantum dots, the battery's response to 400nm-800nm ​​light is enhanced, confirming that carbon quantum dots have a real effect on improving battery performance, rather than being an experimental error.

[0076] like Figure 12As shown, by doping with carbon quantum dots, the TPV response lifetime of the battery almost doubles, indicating an effective reduction in charge recombination. Figure 13 As shown, by doping carbon quantum dots, the carrier extraction and transport speeds are significantly accelerated.

[0077] See Figure 14 The slope of the curve for the undoped carbon quantum dot battery is extremely small, reflecting that the carrier migration in the perovskite bulk is restricted by the trap state, resulting in poor transport dynamics. In contrast, the slope of the curve for the carbon quantum dot-doped battery is significantly increased and shows good linear growth, indicating that the doping of carbon quantum dots effectively passivates the internal defects of the perovskite, reduces the carrier trap density, and improves the carrier migration and transport capabilities from the intrinsic level of the material.

[0078] See Figure 15 The current curve of the undoped carbon quantum dot battery is close to the zero current line, and the overall dark-state electrical response of the device is weak; while the current response amplitude of the carbon quantum dot battery with voltage change is significantly increased, and the dark-state conductivity output capability of the device under electric field drive is substantially improved.

[0079] like Figure 16 As shown, by doping with carbon quantum dots, the battery efficiency and stability were significantly increased, and the more carbon quantum dots were doped, the greater the improvement in battery stability.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing carbon quantum dots, characterized in that, include: Melamine is dissolved in a solvent and then heated in a reaction vessel to obtain the carbon quantum dots.

2. The method for preparing carbon quantum dots according to claim 1, characterized in that, The solvent is methanol, the reaction temperature in the reactor is 180°C, and the reaction time is 36 hours.

3. A carbon quantum dot, characterized in that, The carbon quantum dots were prepared using the method described in claim 1 or 2.

4. The application of carbon quantum dots as described in claim 3 in improving the quality of perovskite film formation.

5. The application of carbon quantum dots as described in claim 3 in the fabrication of perovskite solar cells.

6. A perovskite precursor solution, characterized in that, Including MAPbI3 and carbon quantum dots as described in claim 3.

7. A method for preparing a perovskite precursor solution, characterized in that, include: Weigh MAI and PbI2 in a molar ratio of 1:1 and dissolve them in a mixture of DMF and DMSO to form a first solution; The carbon quantum dots as described in claim 3 are dissolved in a mixture of DMF and DMSO to form a second solution; The first solution and the second solution are mixed to form the perovskite precursor solution.

8. The method for preparing the perovskite precursor solution according to claim 7, characterized in that, The concentration of MAPbI3 in the first solution was 1 mmol / mL, the concentration of carbon quantum dots in the second solution was 25 mg / mL, and the concentration of carbon quantum dots in the perovskite precursor solution was 4 mg / mL.

9. A perovskite solar cell, comprising a conductive glass layer, a hole transport layer, a perovskite layer, an electron transport layer, and an electrode layer arranged sequentially in layers, characterized in that, The perovskite layer is obtained by spin coating with the perovskite precursor liquid as described in claim 6.

10. A method for preparing a perovskite solar cell, characterized in that, include: NiCl2 and NaOH are mixed to obtain NiO. x Nanoparticles, then NiO x Nanoparticles dissolve in deionized water to form NiO x Solution; NiO x The solution is spin-coated onto a conductive glass layer to form a hole transport layer; The perovskite precursor liquid as described in claim 6 is spin-coated onto the hole transport layer to form a perovskite layer. PC 61 BM's chlorobenzene solution is spin-coated onto the perovskite layer to form an electron transport layer; Silver is deposited on the electron transport layer to form an electrode layer.

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